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Biographies of Famous Scientists

Biographies of Famous Scientists, his life and achievements

Biographies of Famous Scientists:

  1. Who is Ada Lovelace: Biography
  2. Who is Albert Einstein: Biography
  3. Who is Alessandro Volta: Biography
  4. Who is Alexander Fleming: Biography
  5. Who is Alexander Graham Bell
  6. Who is Alfred Wegener: Biography
  7. Who is Amedeo Avogadro: Biography
  8. Who is Alfred Russel Wallace
  9. Who is Archimedes: Biography
  10. Who is Aristarchus: Biography
  11. Who is Benjamin Franklin: Biography
  12. Who is Brahmagupta: Biography
  13. Who is Carolus Linnaeus: Biography
  14. Who is Chen-Ning Yang: Biography
  15. Who is David Hilbert: Biography
  16. Who is Dmitri Mendeleev: Biography
  17. Who is Eratosthenes: Biography
  18. Who is Ernest Rutherford: Biography

Who is Ada Lovelace: Biography

Lived 1815 – 18
Born two centuries ago, Ada Lovelace was a pioneer of computing science. She took part in writing the first published program and was a computing visionary, recognizing for the first time that computers could do much more than just calculations.
Early Life and Education
Ada Lovelace was born in London, England on December 10, 18She was named Augusta Ada Byron, but her surname changed after she married.
Her father was the brilliant, yet notorious poet Lord Byron (mad, bad and dangerous to know!) and her mother was Anne Isabella Milbanke. Her father was one of the greats of poetry, but his personality was unstable. Her mother was highly intelligent, had been well-educated by private tutors, and was particularly enthusiastic about mathematics and the sciences.
Ada’s father abandoned his wife and daughter, leaving Britain forever when Ada was one month old. He died in Greece when Ada was eight years old. Ada never knew him.
Ada’s mother, Lady Byron, seems to have had little or no affection for her daughter and had very little contact with her. The young girl was brought up by her maternal grandmother and servants. Her grandmother died when Ada was just seven years old, and Ada herself suffered long spells of poor health in both childhood and later.
One thing her mother insisted upon was that Ada get a high quality education.
In those days, there were no places for girls in the United Kingdom’s universities.
However, girls from wealthy, aristocratic families could still be educated to a high level by private tutors. And this is how Ada was educated.
Her mother wanted Ada to concentrate particularly hard on mathematics and science. She had two reasons for this:
• these were her own favorite subjects
• she was worried that insanity ran in Ada’s father’s family and wanted her daughter to stay away from her father’s interests, such as poetry
Lady Byron also ensured Ada had tuition in music and French, since musical ability and the ability to read and make conversation in French were socially desirable.
Her mother was very strict with Ada. In fact she seems to have been something of a tyrant, demanding that the young girl work very hard and punishing her with periods of isolation if she thought she had not worked hard enough. Lady Byron’s desire was that her daughter would become a highly disciplined, serious person – the opposite of her father.
Ada Lovelace: Mathematician and Computer Scientist
It may seem odd to call someone born in 1815 a computer scientist, but that is what Ada Lovelace became.
Her life changed forever on June 5, 1833, when the 17 year-old girl met Charles Babbage. This was not something many girls Ada’s age could ever do, but as an aristocrat she enjoyed better opportunities than most.
Babbage was Lucasian Professor of Mathematics at the University of Cambridge, a position once held by Isaac Newton and held more recently by Stephen Hawking.
Babbage learned that both Lady Byron and her daughter were knowledgeable about mathematics and invited them to see a small-scale version of the calculating machine he was working on called the difference engine.
Babbage had become fed up with people making mistakes in lengthy calculations, and his idea was to build an infallible steam-driven or hand-cranked calculating machine. Ada was completely captivated by the concept, but there was little she could do at the time to help Babbage with his work.
However, she sent a message to Babbage requesting copies of the machine’s blueprints, because she was determined to understand how it worked.
Learning That You Can Talk to Machines
A Jacquard loom and punch cards. A first step in machine language. Image: George Williams.
Ada and Lady Byron also arranged to visit factories where they could see steam driven machines at work and learn as much as they could about mechanical devices. These were highly unusual activities for an aristocratic woman and her daughter! An important part of Ada’s education was to see the Jacquard loom in operation.
The Jacquard loom was a machine that produced textiles with patterns woven into them. Joseph Marie Jacquard had invented it in 18
The Jacquard loom was controlled by punch cards, with one card equal to one row of the textile being woven. If the card was punched, the loom thread would be raised. If the card was not punched, the loom thread would be left alone. In other words, the punch cards issued instructions to the machine. They were a simple language, or putting it another way, machine code.
More Math and also Marriage & Children
Ada continued her independent pursuit of mathematical knowledge. She became friends with one of the finest female mathematicians of her time, Mary Somerville, who discussed modern mathematics with Ada, set her higher level mathematics problems, and talked in detail about Charles Babbage’s difference engine.
In 1835, at the age of 19, Ada married William King, the Earl of Lovelace, with whom she would have three children between 1836 and 18
In 1841 she began working on mathematics again, and was given advanced work by Professor Augustus De Morgan of University College London. She also continued to learn advanced mathematics through correspondence with Mary Somerville.
All the time, she had kept Babbage’s difference engine in mind.
Ada Lovelace’s Notes on the Analytical Engine
In 1842 Ada Lovelace became aware of a work in French called Sketch of Charles Babbage’s Analytical Engine, by Luigi Federico Menabrea, an engineer.
Menabrea had listened to lectures by Babbage and written them up in French. By this time, Babbage had moved on from the difference engine to a much higher level computer concept, the analytical engine.
The analytical engine would be capable of much more sophisticated calculations than the original difference engine.
Indeed, the analytical engine concept was completely groundbreaking, and a work of incredible genius on Babbage’s part; it was the world’s first programmable computer. In modern terms, the analytical engine would be described as Turing-complete. It featured an arithmetic logic portion, control flow by loops and conditional branching, and separate memory – and all of this to be built using mechanical parts and powered by hand-cranking or steam!
Ada Lovelace got hold of Menabrea’s work and translated it into English.
Babbage read her translation and asked her why she had not written such a paper herself, because she was more than capable. Perhaps she could now add her own thoughts to Menabrea’s work?
Ada Lovelace responded by adding notes to her translation of Menabrea’s work. Her notes were three times more extensive than the original work. When her English translation was published, most of the work published was actually her own.
She also added algebraic workings to the notes for how an analytical engine could perform calculations. Babbage himself took on one of the trickiest calculations – Bernoulli Numbers – and sent it to Ada to include in her work, but she detected and corrected what Babbage himself described as ‘a grave error’ in his working. In her notes, she included the world’s first published computer program, or algorithm – this was the Bernoulli number algorithm – and hence she is often cited as the world’s first computer programmer. It would be fair to say, though, that Babbage contributed much of this section of her notes – precisely how much is the subject of academic debate.
In her notes Ada Lovelace broke new ground in computing, when she realized something that nobody else had. She realized that an analytical engine could go beyond numbers. This was the first ever conception of a modern computer – not just a calculator – but a machine that could contribute to other areas of human endeavor, for example to compose music.
Ada Lovelace had grasped that anything that could be converted into numbers, such as music, or the alphabet (language) or images, could then be manipulated by computer algorithms. An analytical engine had the potential to revolutionize the way the whole world worked, not just the world of mathematics.
She wrote, for example:
… Supposing, for instance, that the fundamental relations of pitched sounds in the science of harmony and of musical composition were susceptible of such expression and adaptations, the engine might compose… pieces of music of any degree of complexity or extent.
Ada Lovelace, 1815 – 1852
Ada’s notes indicate that her mental processes had evolved further than her mother’s strictly disciplined approach. She had become comfortable with a more visionary approach. Yes, it’s true that her notes are full of mathematics, but she had freed her mind sufficiently to look beyond the equations and algorithms to other possibilities. Babbage himself described her as ‘an enchantress of numbers.’
However, this was not destined to be the brilliant dawn of a new science.
Ada Lovelace became increasingly unwell after she wrote her notes and died young. Charles Babbage ran into financial problems, which meant that he never built a working computer.
An important question to ask at this stage is: could one of Babbage’s mechanical computers ever have worked in practice?
The working difference engine at the Science Museum in London. Image: Geni.
Fortunately, we know the answer to this. In 1991, Doron Swade, Curator of Computing at London’s Science Museum, had a difference engine built using Babbage’s design.
It weighed 5 tons and worked perfectly. One or two small design errors had to be corrected, although it is likely that these were deliberate errors aimed at preventing a competitor or foreign government building an engine easily if they could steal the plans.
Enter Alan Turing
About 90 years after Ada Lovelace wrote her notes, Alan Turing entered the field. Turing, of course, was a genius in his own right.
As a young man he had read Ada Lovelace’s notes, among many other papers he read. We know he disagreed with one of her conclusions – that artificial intelligence is not possible. She believed that computers could only ever follow instructions, and could never ‘think’ independently. Turing demonstrated that she was wrong.
Unfortunately, with no means of asking him the question, we cannot say to what extent Ada Lovelace’s work actually influenced his concept of The Universal Turing Machine, the machine concept that began the modern age of computing.
Certainly the mathematics involved in the development of the Universal Turing Machine is beyond anything done in Babbage and Lovelace’s time. On the other hand, the concept of a machine that could be more than a calculator, to compose music, for example, began with Lovelace’s notes.
A Colossus computer at Bletchley Park being used to decode German messages sent during World War
The codebreakers at Bletchley Park in the United Kingdom, where Turing worked during World War 2, built and used the Colossus series of computers – the world’s first electronic computers. In doing so, they actually put Lovelace’s visionary concept of a computer to work. Coded text from German messages was converted to numbers which could then undergo statistical analysis by the computer before being converted back into text that could be read and understood by humans.
The Mother of Modern Computing?
So, is it correct to describe Ada Lovelace as the mother of our modern concept of computing?
If we’re using language like mothers and fathers, I think we’re on pretty safe ground to say that Ada Lovelace is the mother of modern computing, and Charles Babbage is the father.
What we can’t say for certain is:
Did Ada and Charles’s child die in infancy, so that Turing’s computing breakthroughs represented an entirely new child?
or
Did Ada and Charles’s child live on in some kind of suspended animation until it was rediscovered, adopted and reared into adulthood by Alan Turing.
We shall probably never know the answer.
What we do know is that the Pentagon and US military’s programmers named their own computing language Ada.
The End
Ada Lovelace died, probably of uterine cancer, at the age of 36 on November 27, 18Her health had deteriorated after she completed her notes on the analytical engine, and she had suffered a variety of illnesses. She had been in pain for several years, and was given opiates by her physicians to help her cope with it. She also drank considerable amounts of alcohol, affecting her moods in her later years.
In the end, she forgave her father for abandoning her as a baby. She came to believe that her mother had deliberately tried to turn her against her father. Ada requested that she be buried beside Lord Byron at the Church of St. Mary Magdalene, Hucknall, Nottingham. Her grave can be seen there today.
We’ll end with the words penned by Lord Byron at the beginning of one of his greatest works Childe Harold’s Pilgrimage soon after he left his wife and baby daughter forever:
Is thy face like thy mother’s, my fair child!
Ada! sole daughter of my house and heart?
When last I saw thy young blue eyes, they smiled,
And then we parted, not as now we part,
But with a hope.
Lord Byron, 1788 – 1824

Who is Albert Einstein: Biography

Lived 1879 – 19
Albert Einstein rewrote the laws of nature.
He completely changed the way we understand the behavior of things as basic as light, gravity, and time.
Although scientists today are comfortable with Einstein’s ideas, in his time, they were completely revolutionary. Most people did not even begin to understand them.
If you’re new to science, you’ll probably find that some of his ideas take time to get used to!
Quick Guide to Albert Einstein’s Scientific Achievements
Albert Einstein:
• provided powerful confirmation that atoms and molecules actually exist, through his analysis of Brownian motion.
• demonstrated the photoelectric effect, establishing that light can behave as both a wave and a particle. Light particles (he called them quanta) with the correct amount of energy can eject electrons from metals.
• proved that everyone, whatever speed we move at, measures the speed of light to be 300 million meters per second in a vacuum. This led to the strange new reality that time passes more slowly for people traveling at very high speeds compared with people moving more slowly.
• discovered the hugely important and iconic equation, E = mc2, which showed that energy and matter can be converted into one another.
• rewrote the law of gravitation, which had been unchallenged since Isaac Newton published it in 16In his General Theory of Relativity, Einstein:
» showed that matter causes space to curve, which produces gravity.
» showed that the path of light follows the gravitational curve of space.
» showed that time passes more slowly when gravity becomes very strong.
• became the 20th century’s most famous scientist when the strange predictions he made in his General Theory of Relativity were verified by scientific observations.
• spent his later years trying to find equations to unite quantum physics with general relativity. This was an incredibly hard task for him to set himself. To date, it has still not been achieved.
His Beginnings
Albert Einstein was born on March 14, 1879 in Ulm, Germany. He was not talkative in his childhood, and until the age of three, he didn’t talk much. He spent his teenage years in Munich, where his family had an electric equipment business. As a teenager, he was interested in nature and showed a high level of ability in mathematics and physics.
Einstein loved to be creative and innovative. He loathed the uncreative spirit in his school at Munich. His family’s business failed when he was aged 15, and they moved to Milan, Italy. Aged 16, he moved to Switzerland, where he finished high school.
In 1896 he began to study for a degree at the Swiss Federal Institute of Technology in Zurich. He didn’t like the teaching methods there, so he bunked classes to carry out experiments in the physics laboratory or play his violin. With the help of his classmate’s notes, he passed his exams; he graduated in 19
Einstein was not considered a good student by his teachers, and they refused to recommend him for further employment.
Einstein 1903
While studying at the Polytechnic, Einstein had learned about one of the biggest problems then baffling physicists. This was how to marry together Isaac Newton’s laws of motion with James Clerk Maxwell’s equations of electromagnetism.
In 1902 he obtained the post of an examiner in the Swiss Federal patent office, and, in 1903, he wedded his classmate Mileva Maric. He had two sons with her but they later divorced. After some years Einstein married Elsa Loewenthal.
Early Scientific Publications
Einstein continued to work in the patent office, during which time he made most of his greatest scientific breakthroughs. The University of Zurich awarded him a Ph.D. in 1905 for his thesis “A New Determination of Molecular Dimensions.”
1905: The Year of Miracles
In 1905, the same year as he submitted his doctoral thesis, Albert Einstein published four immensely important scientific papers dealing with his analysis of:
• Brownian motion
• the equivalence of mass and energy
• the photoelectric effect
• special relativity
Each of these papers on their own was a huge contribution to science. To publish four such papers in one year was considered to be almost miraculous. Einstein was just 26 years old.
Mass Energy Equivalence
Einstein gave birth in 1905 to what has become the world’s most famous equation:
E = mc2
The equation says that mass (m) can be converted to energy (E). A little mass can make a lot of energy, because mass is multiplied by c2 where c is the speed of light, a very large number.
A small amount of mass can make a large amount of energy. Conversion of mass in atomic nuclei to energy is the principle behind nuclear weapons and explains the sun’s source of energy.
The Photoelectric Effect
If you shine light on metal, the metal may release some of its electrons. Einstein said that light is made up of individual ‘particles’ of energy, which he called quanta. When these quanta hit the metal, they give their energy to electrons, giving the electrons enough energy to escape from the metal.
Einstein showed that light can behave as a particle as well as a wave. The energy each ‘particle’ of light carries is proportional to the frequency of the light waves.
Einstein’s Special Theory of Relativity
In Einstein’s third paper of 1905 he returned to the big problem he had heard about at university – how to resolve Newton’s laws of motion with Maxwell’s equations of light. His approach was the ‘thought experiment.’ He imagined how the world would look if he could travel at the speed of light.
He realized that the laws of physics are the same everywhere, and regardless of what you did – whether you moved quickly toward a ray of light as it approached you, or quickly away from the ray of light – you would always see the light ray to be moving at the same speed – the speed of light!
This is not obvious, because it’s not how things work in everyday life, where, for example, if you move towards a child approaching you on a bike he will reach you sooner than if you move away from him. With light, it doesn’t matter whether you move towards or away from the light, it will take the same amount of time to reach you. This isn’t an easy thing to understand, so don’t worry about it if you don’t! (Unless you’re at university studying physics.) Every experiment ever done to test special relativity has confirmed what Einstein said.
If the speed of light is the same for all observers regardless of their speed, then it follows that some other strange things must be true. In fact, it turns out that time, length, and mass actually depend on the speed we are moving at. The nearer the speed of light we move, the bigger differences we seen in these quantities compared with someone moving more slowly. For example, time passes more and more slowly as we move faster and faster.
Einstein Becomes Known to the Wider Physics Community
As people read Einstein’s papers and argued about their significance, his work gradually gained acceptance, and his reputation as a powerful new intellect in the world of physics grew. In 1908 he began lecturing at the University of Bern, and the following year resigned from the Patent Office. In 1911 he became a professor of physics at the Karl-Ferdinand University in Prague, before returning to Zurich in 1912 to a professorship there.
Working on the general theory of relativity, in 1911 he made his first predictions of how our sun’s powerful gravity would bend the path of light coming from other stars as it traveled past the sun.
The General Theory of Relativity – Einstein Becomes Famous Worldwide
A very, very rough approximation: the earth’s mass curves space. The moon’s speed keeps it rolling around the curve rather than falling to Earth. If you are on Earth and wish to leave, you need to climb out of the gravity well
Einstein published his general theory of relativity paper in 1915, showing, for example, how gravity distorts space and time. Light is deflected by powerful gravity, not because of its mass (light has no mass) but because gravity has curved the space that light travels through.
In 1919 a British expedition traveled to the West African island of Principe to observe an eclipse of the sun. During the eclipse they could test whether light from far away stars passing close to the sun was deflected. They found that it was! Just as Einstein had said, space truly was curved.
On November 7, 1919, the London Times’ headline read:
Revolution in science – New theory of the Universe – Newtonian ideas overthrown.
Honors and More Honors
Albert Einstein was awarded the Nobel Prize in Physics in 19People are sometimes surprised to learn that the award was not made for his work in special or general relativity, but for his overall services to theoretical physics and one of the works from his miracle year specifically – the discovery of the law of the photoelectric effect in 19
The Royal Society of London awarded him its prestigious Copely Medal in 1925 for his theory of relativity and contributions to the quantum theory. The Franklin Institute awarded him with the Franklin medal in 1935 for his work on relativity and the photo-electric effect.
Universities around the world competed with one another to award him honorary doctorates, and the press wrote more about him than any other scientist – Einstein became a celebrity.
Einstein’s Later Years
Einstein made his greatest discoveries when he was a relatively young man.
In his later years he continued with science, but made no further groundbreaking discoveries. He became interested in politics and the state of the world.
Einstein had been born German and a Jew. He died an American citizen in 19Einstein was in America when Hitler came to power. He decided it would be a bad idea to return to Germany, and renounced his German citizenship. Einstein did not practice Judaism, but strongly identified with the Jewish people persecuted by the Nazi Party, favoring a Jewish homeland in Palestine with the rights of Arabs protected.
It was Einstein’s wish that people should be respected for their humanity and not for their country of origin or religion. Expressing his cynicism for nationalistic pride, he once said:
“If relativity is proved right the Germans will call me a German, the Swiss will call me a Swiss citizen, and the French will call me a great scientist. If relativity is proved wrong, the French will call me Swiss, the Swiss will call me a German, and the Germans will call me a Jew.”

Who is Alessandro Volta: Biography

Alessandro Volta was a physicist, chemist and a pioneer of electrical science. He is most famous for his invention of the electric battery. In brief he:
• Invented the first electric battery – which people then called the “voltaic pile” – in 18Using his invention, scientists were able to produce steady flows of electric current for the first time, unleashing a wave of new discoveries and technologies.
• Was the first person to isolate methane.
• Discovered methane mixed with air could be exploded using an electric spark: this is the basis of the internal combustion engine.
• Discovered “contact electricity” resulting from contact between different metals.
• Recognized two types of electric conduction.
• Wrote the first electromotive series. This showed, from highest to lowest, the voltages that different metals can produce in a battery. (We now talk of standard electrode potentials, meaning roughly the same thing.)
• Discovered that electric potential in a capacitor is directly proportional to electric charge.
In recognition of Alessandro Volta’s contributions to electrical science, the unit of electric potential is called the volt.
Early Life and Education
Alessandro Volta was born in Como, Lombardy, Italy, on February 18, 17His family was part of the nobility, but not wealthy. Until the age of four, he showed no signs of talking, and his family feared he was not very intelligent or possibly dumb. Fortunately, their fears were misplaced.
When he was seven, his father died leaving unpaid debts. The young Alessandro Volta was educated at home by his uncle until he was twelve years old. He then started studies at a Jesuit boarding school. The Jesuit school charged no fees, but pressurized him to become a priest. His family did not want this, and withdrew him from the school after four years. Volta then studied at the Benzi Seminary until reaching eighteen years of age.
Volta’s family wanted him to become a lawyer. Volta had his own ideas! He was interested in the world around him; he wanted to be a scientist.
Although as a child he had been slow to speak Italian, Volta now seemed to have a special talent for languages. Before he left school, he had learned Latin, French, English and German. His language talents helped him in later life, when he traveled around Europe, discussing his work with scientists in Europe’s centers of science.
Aged 18, Volta was bold enough to begin an exchange of letters about electricity with two leading physicists: Jean-Antoine Nollet in Paris, and Giambatista Beccaria in Turin. Beccaria did not like some of Volta’s ideas and encouraged him to learn more by doing experiments.
When he wrote his first dissertation, Volta addressed it and dedicated it to Beccaria.
“You must be ready to give up even the most attractive ideas when experiment shows them to be wrong.”
Alessandro Volta
Volta’s Career Timeline Before the Battery
Amateur Scientist, Inventor, Teacher and Physics Professor
1765 – Volta had reached 20 years of age. His wealthy friend Giulio Cesare Gattoni had built a physics laboratory in his home. For several years he kindly allowed Volta to do experiments in this laboratory.
1765 – Volta wrote his first scientific paper, which he addressed to Giambatista Beccaria, about static electricity generated by rubbing different substances together – i.e. triboelectricity.
1769 – Volta published a dissertation titled On the Attractive Force of the Electric Fire, and on the Phenomena Dependent On It, which he sent to Beccaria. He discussed his ideas on the causes of electrical attraction and repulsion and compared these with gravity. He set out his position that, like gravity, static electricity involved action at a distance. The main scientists influencing his thinking were Isaac Newton, Roger Boscovich, Benjamin Franklin and Giambatista Beccaria himself.
1771 – Volta read Joseph Priestley’s 1767 review of scientific research on electricity. He learned that some discoveries he had made recently had already been made by others.
1774 – Volta began work overseeing schools in Como. He said that teaching in Como’s classrooms should be modernized. He wanted the children to spend more time learning science and modern languages.
1775 – Volta began teaching experimental physics in Como’s public grammar school, where he worked until 17
1775 – Volta wrote a letter to Joseph Priestley. He explained how he had invented a device which was a source of static electricity: the electricity could be transferred to other objects. We call this device the electrophorus. Volta wanted to know if the device was a new invention. Priestly told him Johann Wilcke had invented such a device in 1762, but Volta had invented it independently. Priestley encouraged Volta to keep up his interesting research work.
1776 – Aged 31, Volta was the first person to isolate methane gas. He discovered that a methane-air mixture could be exploded in a closed container with an electric spark. In the future, an electrically started chemical reaction like this would be the basis of the internal combustion engine.
1776 – Volta suggested that the sparking apparatus he used to explode methane could also be used to send an electric signal along a wire from Como to the city of Milan.
“What is it possible to do well, in physics particularly, if things are not reduced to degrees and measures?”
Alessandro Volta, 1792
1777 – Volta invented a much better eudiometer than any that had gone before. A eudiometer tests how much oxygen is present in air to determine how good for breathing it is. Volta’s eudiometer was superior to others because it used hydrogen as the gas reacting with oxygen, giving a clean, reliable reaction. The reaction was also cleanly started using an electric spark. The eudiometer worked on the basis that the decrease in volume of hydrogen after sparking was proportional to the amount of oxygen present in air.
1777 – Volta set out on a scientific journey to Switzerland and France. He met other scientists and showed them his innovations in electrical equipment. He also traveled so that his name would become better known outside Italy.
1778 – Volta was appointed to the Chair of Experimental Physics at the University of Pavia, about 55 miles (85 km) from Como, a position he would hold for over 40 years.
1778 – Volta discovered that the electrical potential (we now often call this the voltage) in a capacitor is directly proportional to electrical charge.
1781 to 1782 – Volta traveled around most of Europe’s major scientific centers, including the French Academy in Paris, demonstrating his electrical equipment and inventions to eminent people such as Antoine Lavoisier and Benjamin Franklin. Volta was beginning to become well-known outside Italy.
1782 – Volta wrote about the condenser he had constructed (today we would call it a capacitor) to collect and store electric charge, and how he had used it to study a variety of electrical phenomena.
1788 – Volta built increasingly sensitive electroscopes to detect and measure the effects of electric charge.
1790 – Volta carried out experiments on the behavior of gases. He found an accurate value for air’s increasing volume with rising temperature.
1791 – Recognizing that he had become one of Europe’s foremost electrical scientists, Volta was elected to be a Fellow of the Royal Society of London.
1794 – At the age of 50, Volta was awarded the Royal Society’s top prize – the Copley Medal – for his contributions to scientific understanding of electricity.
Invention of the Electric Battery
A Feud over Frogs’ Legs led to the Battery
Volta did not set out to invent the battery. His experiments in this area were actually performed to show the claims of another scientist were wrong. That scientist was another Italian, Luigi Galvani.
Jumping Frogs’ Legs
Galvani discovered that contact between frog leg nerves and different metals caused the legs to move. We now understand that he had created an electric cell. The frog legs acted as the electrolyte and also moved when stimulated by the flow of electricity.
Galvani was a professor of anatomy. In the late 1780s he noticed that a spark of static electricity carried by a metal scalpel touching the nerves of a dead frog while the legs lay on metal caused the legs to move. This was an amazing discovery: animal movement was based on electricity in some way.
In 1817, this led to Mary Shelley writing Frankenstein. In this novel, a creature made from a monstrous mixture of body parts from dead people is brought to life by Doctor Frankenstein using electricity from a lightning storm.
In 1791, Galvani announced his discovery of animal electricity. He believed that animals generated electricity in their bodies and that a fluid within animals’ nerves carried electricity to muscles, causing movement. He believed that electricity from an outside source released a flow of electrical fluid from the nerves, causing the muscles to jump.
He also believed that animals such as electric eels could build up extra amounts of this fluid and use it to deliver electric shocks.
Galvani concluded that animal electricity was similar to static electricity, but it was different and was a unique property of living things.
Enter Volta
Volta studied Galvani’s phenomenon.
In 1792, Volta said that the “animal” part of Galvani’s animal electricity was not needed. Animals merely responded to normal electricity. There was no difference between animal electricity and electricity.
Volta performed various experiments on frogs’ legs. He found the key to getting them to move was contact with two different metals. Contact with pieces of the same metal did nothing.
Then, moving away from frogs’ legs, in 1794, Volta did experiments to measure the electrical effect of bringing different pairs of metals into contact. He listed the metals in order of what he called their electromotive force.
Volta’s List Of Conductors, Highest Electromotive Force First
Zinc
Lead
Tin
Iron
Copper
Silver
Gold
Graphite
Manganese Ore
This was the first time anyone had listed electrode potentials. It was the first electrochemical series.
In modern language, we would say that the farther apart the substances on this list are, the greater the voltage they will produce when brought into contact or used as the electrodes in electric cells and batteries. For example, a zinc-graphite cell will produce a greater voltage than a zinc-lead cell.
By 1797, Volta had completely proved his “contact theory” of electricity.
He now knew that the key to producing what today we call a voltage was two metals connected by by something moist, like frogs’ legs. The moist connection between the metals did NOT have to be an animal. Connecting the metals by placing them in a cup of dilute acid was a very effective way of producing electricity.
He formally split electrical conductors into those of the first kind: these were metals, graphite and pure charcoal; and the second kind: these were substances we would now call electrolytes, such as salt water or dilute acids. An electric current would result when a circuit was built using two conductors of the first kind combined with one of the second kind.
An illustration from Volta’s 1800 paper. Pieces of silver (A) and zinc (Z) connected by metal strips and sitting in cups of dilute acid will produce electricity. This could be tested by putting a finger in each of the end cups. You would get an electric shock. Unlike Galvani’s version, no animals need be hurt in this production, except for the human tester who gets a mild electric shock.
Alternatively, connecting the metals with paper soaked in dilute acid or salt water also worked.
Volta said that in Galvani’s work, the frogs’ legs had served two functions:
• They conducted electricity as conductors of the second kind.
• They acted as a very sensitive electroscope. (An electroscope is a device used to detect electricity.)
Diagram from Volta’s 1800 paper. The pile is made using discs of silver (A) and zinc (Z) linked in series with card soaked in salt water. The positive and negative polarities of this battery are as shown. Adding more pairs of discs increases the voltage of the battery.
Volta found that by connecting up more and more pairs of metals connected with moist card, he could produce ever higher voltages, leading to significant electrical currents.
And so the electrical battery was born.
Volta used alternating zinc and silver discs linked by card or cloth soaked in salt water.
In 1800, Volta described his results in a letter to Joseph Banks, at the Royal Society in London.
Banks showed the letter to other scientists, and arranged for Volta’s description of his discovery to be read out at a meeting of the Society and published.
“I continue coupling a plate of silver with one of zinc, and always in the same order… and place between each of these couples a moistened disk. I continue to form a column. If the column contains about twenty of these couples of metal, it will be capable of giving to the fingers several small shocks.”
Alessandro Volta, 1800
Volta’s Battery Unleashed a Wave of New Scientific Discoveries
The battery that Volta had invented gave chemists a very powerful new method to study substances.
The beauty of Volta’s device was that almost anyone could make one – silver and copper coins were available to many people, as were other metals such as iron, tin and zinc.
Within weeks of Volta’s invention of the battery, William Nicholson and Anthony Carlisle built and used a battery to decompose water into hydrogen and oxygen.
Within just six years, Humphry Davy had built a powerful battery. With it, he isolated new chemical elements, and deduced that chemical bonds were electrical in nature.
Volta demonstrates his battery to Napoleon Bonoparte in 18Napoleon was very impressed by Volta’s work, giving him the aristocratic title of Count.
Davy’s discoveries of the new elements barium, calcium, lithium, magnesium, potassium, sodium, and strontium, were all made possible by Volta’s invention of the battery.
By 1820, courtesy of Volta’s batteries, Hans Christian Oersted was investigating the relationship between electricity and magnetism.
By 1821, Michael Faraday had produced an electric motor.
Volta’s battery produced a steady source of electric current for the first time ever. All electrical devices depend on electric current. Without Volta’s invention, there could be no modern technology. Volta’s battery was an absolutely crucial invention in the development of our technology based civilization.
The End
In 1819, at the age of 74, Volta decided it was time to hang up his capacitors, his voltaic piles, his electrophorus, and his administrative work at the university. He retired to a country house close to his home town of Como, where he could spend more time with his wife, Maria Teresa. They had three sons, Zanino, Faminio and Luigi.
Volta lived in Como until his death, aged 82, on March 5, 18
In 1881, scientists decided that the unit of electric potential would be called the volt to recognize Volta’s great contributions to electrical science.

Who is Alexander Fleming: Biography

Lived 1881 – 19
Alexander Fleming discovered penicillin, whose use has saved untold millions of lives. Less well-known is that before making this world-changing discovery, he had already made significant contributions to medical science.
Beginnings
Alexander Fleming was born on August 6, 1881 at his parents’ farm located near the small town of Darvel, in Scotland, UK.
His parents, Hugh Fleming and Grace Stirling Morton, were both from farming families. His father’s health was fragile; he died when Alexander was just seven years old.
Alexander’s earliest schooling, between the ages of five and eight, was at a tiny moorland school where 12 pupils of all ages were taught in a single classroom.
Darvel School was Alexander’s next school, which involved an eight-mile round trip walk every school-day. At the age of 11 his academic potential was recognized and he was awarded a scholarship to Kilmarnock Academy, where he boarded for about two years before leaving for the city of London.
Alexander arrived in London early in 1895, aged This was the year his fellow Scot, Arthur Conan Doyle, published The Memoirs of Sherlock Holmes, in which readers were horrified to learn that their hero had died falling over the Reichenbach Falls.
Alexander lived in the home of an older brother, Tom, who was a doctor of medicine. Most of the Fleming family ended up living with Tom, leaving the eldest brother, Hugh, running the farm.
Alexander attended the Polytechnic School, where he studied business and commerce. He started in a class appropriate to his age, but his teachers soon realized he needed more challenging work. He was moved into a class with boys two years older than him and finished school aged
Work and Medical School
His business training helped him get a job in a shipping office, but he did not enjoy working there.
In 1901, at the age of 20, he inherited some money from his uncle, John Fleming. He decided to use the money to go to medical school; he wanted to become a doctor like his successful brother Tom.
First, he needed suitable qualifications to enable him to join a medical school. This did not present any great difficulties; he passed his exams with the highest marks of any student in the United Kingdom.
In 1903, aged 22, Alexander enrolled at London’s St Mary’s Hospital Medical School, graduating with distinction three years later as Bachelor of Medicine, Bachelor of Surgery.
Rather than follow in Tom’s footsteps, Alexander was persuaded by Almroth Wright, an authority in immunology, to become a researcher in his bacteriology group at St Mary’s Hospital Medical School. While carrying out this research Fleming graduated, in 1908, with a degree in bacteriology and the Gold Medal for top student. St Mary’s Hospital Medical School then promoted him to the role of bacteriology lecturer.
Almroth Wright was interested in our bodies’ natural ability to fight infection. Fleming became particularly fascinated by the fact that, although many people suffered bacterial infections from time to time, the majority of people’s natural defenses prevented infections from taking hold.
Fleming’s Most Significant Contributions to Science
Proving that Antiseptics Kill rather than Cure
In 1914 World War 1 broke out and Fleming, aged 33, joined the army, becoming a captain in the Royal Army Medical Corps, working in field hospitals in France.
There, in a series of brilliant experiments, he established that antiseptic agents used to treat wounds and prevent infection were actually killing more soldiers than the infections were!
The antiseptics, such as carbolic acid, boric acid and hydrogen peroxide, were failing to kill bacteria deep in wounds; worse, they were in fact lowering the soldier’s natural resistance to infection because they were killing white blood cells.
Fleming demonstrated that antiseptic agents were only useful in treating superficial wounds, but were harmful when applied to deep wounds.
Almroth Wright believed that a saline solution – salt water – should be used to clean deep wounds, because this did not interfere with the body’s own defenses and in fact attracted white cells. Fleming proved this result in the field.
Wright and Fleming published their results, but most army doctors refused to change their ways, resulting in many preventable deaths.
Nurses come to the aid of a wounded soldier. Fleming saved many soldiers’ lives in World War One by washing deep wounds with saline solution rather than the antiseptics recommended by medical textbooks.
Discovery of Lysozyme
In 1919 Fleming returned to research at St Mary’s Hospital Medical School in London. His wartime experience had firmly established his view that antibacterial agents should only be used if they worked with the body’s natural defenses rather than against them; in particular, they must not harm white blood cells.
His first discovery of such an agent came in 1922, when he was 41 years old.
Fleming had taken secretions from inside the nose of a patient suffering from a head cold. He cultured the secretions to grow any bacteria that happened to be present. In the secretions, he discovered a new bacterium he called Micrococcus lysodeikticus, now called M luteus.
A few days later, Fleming was examining these bacteria. He himself was now suffering from a head cold, and a drop of mucus fell from his nose on to the bacteria. The bacteria in the area the drop had fallen were almost instantly destroyed. Always on the lookout for natural bacteria killers, this observation excited Fleming enormously.
He tested the effect of other fluids from the body, such as blood serum, saliva, and tears, on these bacteria and found that bacteria would not grow where a drop of one of these fluids had been placed.
Fleming discovered the common factor in the fluids was an enzyme.
He named his newly discovered enzyme lysozyme. The effect of lysozyme was to destroy certain types of microbe, rendering them harmless to people. The presence of lysozyme in our bodies prevents some potentially pathogenic microbes from causing us harm. It gives us natural immunity to a number of diseases.
However, lysozyme’s usefulness as a medicine is rather limited, because it has little or no effect on many other microbes that infect humans.
It did, however, mean that Fleming had discovered a natural antibiotic which did not kill white blood cells. If only he could find a more powerful antibiotic, then medicine could be transformed.
Today, lysozyme is used as a food and wine preservative. It is naturally present in especially large concentrations in egg-whites, offering protection against infection to chicks.
It is also used in medicines, particularly in Asia, where it is used in treatments for head colds, athlete’s foot and throat infections.
Lysozyme is shown here in blue. It is an enzyme, meaning it is a type of protein. It destroys bacteria by breaking down their cell walls, shown in pink.
“The view has been generally held that the function of tears, saliva and sputum, so far as infections are concerned, was to rid the body of microbes by mechanically washing them away… however, it is quite clear that these secretions, together with most of the tissues of the body, have the property of destroying microbes to a very high degree.”
Alexander Fleming
Bacteriologist
Discovery of Penicillin
In the month of August 1928, Fleming did something very important. He enjoyed a long vacation with his wife and young son.
On Monday, September 3, he returned to his laboratory and saw a pile of Petri dishes he had left on his bench. The dishes contained colonies of Staphylococcus bacteria. While he was away, one of his assistants had left a window open and the dishes had become contaminated by different microbes.
Annoyed, Fleming looked through the dishes and found something remarkable had taken place in one of them.
A fungus was growing and the bacterial colonies around it had been killed. Farther from the fungus, the bacteria looked normal. Excited by his observation, he showed the dish to an assistant, who remarked on how similar this seemed to Fleming’s famous discovery of lysozyme.
Hoping he had discovered a better natural antibiotic than lysozyme, Fleming now devoted himself to growing more of the fungus. He identified that it belonged to the Penicillium genus and that it produced a bacteria-killing liquid. On March 7, 1929 he formally named the antibiotic – it would be known as penicillin.
Fleming published his results, showing that penicillin killed a variety of bacteria which were then the scourge of humanity, including those responsible for scarlet fever, pneumonia, meningitis and diphtheria. Furthermore, penicillin was non-toxic and it did not attack white blood cells.
Unfortunately, the scientific world was largely underwhelmed, ignoring his discovery.
Fleming faced a number of problems:
• it was difficult to isolate penicillin from the fungus producing it
• he could not find a way of producing penicillin in high concentrations
• penicillin seemed to be slow acting
• clinical tests of penicillin as a surface antiseptic showed it was not especially effective
• Fleming’s boss, Almroth Wright, had a generalized dislike of chemists and refused to allow them in his laboratory. The presence of a skilled chemist would have been a huge benefit in terms of isolating, purifying, and concentrating penicillin.
Regardless of these issues, Fleming continued with some work on penicillin in the 1930s, but never made the breakthrough he needed to produce it in large, concentrated quantities. Others, however, did.
In the early 1940s a large team of University of Oxford scientists led by pharmacologist Howard Florey and biochemist Ernst Boris Chain finally transformed penicillin into the medicine we know today.
In 1945 Alexander Fleming shared the Nobel Prize in Medicine or Physiology with Florey and Chain. The award was made:
“for the discovery of penicillin and its curative effect in various infectious diseases.”
In his Nobel Prize winning speech in 1945, Fleming warned of a danger which today is becoming ever more pressing:
“It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them, and the same thing has occasionally happened in the body. The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant.”
Alexander Fleming
Bacteriologist
Fleming was always fulsome in his praise for Florey, Chain, and their team, and he downplayed his own role in penicillin’s story. Despite his modesty, he became a worldwide hero. Millions of people owed their lives to the antibiotic he had discovered.
In 1945 he toured America, where chemical companies offered him a personal gift of $100,000 as a mark of respect and gratitude for his work. Typically of Fleming, he did not accept the gift for himself: he donated it to the research laboratories at St Mary’s Hospital Medical School.
Some Personal Details and the End
In 1915, while a captain in the Medical Corps, Fleming married Sarah Marion McElroy. Their only son, Robert, became a general medical practitioner.
In 1944 he was knighted and became Sir Alexander Fleming.
His wife Sarah died in 19
In 1953 Fleming married Dr. Amalia Koutsouri-Voureka, who was working in his research group at St Mary’s Hospital Medical School.
Alexander Fleming died aged 73 of a heart attack in London on March 11, 19His ashes were placed in St Paul’s Cathedral.

Who is Alexander Graham Bell

Alexander Graham Bell invented the telephone. Remarkably, he only worked on his invention because he misunderstood a technical work he had read in German. His misunderstanding ultimately led to his discovery of how speech could be transmitted electrically.
Images are: A model of Bell’s very first telephone (top-left). Alexander Graham Bell in 1874, aged 26, when he became a professor at Boston University (bottom-left). Bell, aged 45, making the first call from New York to Chicago when the exchange opened in 1892 (right).
Alexander Graham Bell’s Early Life, Early Inventions, and Education
Alexander Graham Bell was born March 3, 1847 in Edinburgh, Scotland. His mother’s name was Eliza Grace Symonds.
His father, Alexander Melville Bell, was a professor of speech elocution at the University of Edinburgh. His father also wrote definitive books about speech and elocution, which sold very well in the UK and North America.
The young Alexander was home-schooled until he was 11, following which he attended Edinburgh’s Royal High School for four years: he enjoyed science, but did not do well academically.
Although his schoolwork was poor, his mind was very active. One day, he was playing at a flour mill owned by the family of a young friend. Bell learned that de-husking the wheat grains took a lot of effort and was also very boring. He saw that it would be possible for a machine to do the work, so he built one. He was only 12 at the time. The machine he built was used at the mill for several years.
Aged 15, he joined his grandfather who had moved to London, England. His grandfather home-schooled him, which seemed to bring out the best in Bell again. When he was 16, he enrolled at Weston House Academy in Elgin, Scotland, where he learned Greek and Latin and also earned some money teaching elocution.
While he was 16, he and his brother tried to build a talking robot. They built a windpipe and a realistic looking head. When they blew air through the windpipe, the mouth could make a small number of recognizable words.
For the next few years, Bell moved to a new school most years, either teaching elocution or improving his own education.
To Canada
While Bell moved around a lot, he continued to carry out his own research into sound and speech. He worked very hard indeed, and by the time he was 20 he was in very poor health and returned to his family home, which was now in London.
By mid-1870, when Bell was 23, both of his younger brothers had died of tuberculosis. Bell’s parents were terrified that Alexander, whose health was fragile, would suffer a similar fate. He was now the only child of theirs who was still alive.
Bell’s father had gone to Canada when he was younger and found that his poor health had improved dramatically. He now decided that what was left of his family should move to Canada, and by late 1870, they were living in Brentford, Ontario. Thankfully, Alexander Graham Bell’s health began to improve.
While living in Brentford, Bell learned the Mohawk language and put it in writing for the first time. The Mohawk people made him an Honorary Chief.
And the United States
When he was 25, Bell opened his School of Vocal Physiology and Mechanics of Speech in Boston, MA, where he taught deaf people to speak. At age 26, although he did not have a university degree, he became Professor of Vocal Physiology and Elocution at the Boston University School of Oratory.
The Invention of the Telephone
While he was moving jobs and locations around the UK and North America, Bell had developed an overriding desire to invent a machine that could reproduce human speech.
Speech had become his life: his mother had gone deaf, and Bell’s father had developed a method of teaching deaf people to speak, which Bell taught. His research into mechanizing human speech had become a relentless obsession: in the UK it had driven him almost to collapse.
When Bell was only 19 years old, he had described the work was doing in a letter to the linguistics expert Alexander Ellis. Ellis told Bell his work was similar to work carried out in Germany by Hermann von Helmholtz.
A Mistake Puts Bell on the Right Track
Bell eagerly read Helmholtz’s work, or tried to read it. It was in German, which he did not understand. Instead, he tried to follow the logic of the book’s diagrams. Bell misunderstood the diagrams, believing that Helmholtz had been able to convert all of the sounds of speech to electricity.
In fact, Helmholtz had not been able to do this – he had only succeeded with vowel sounds – but from then on, Bell believed it could be done!
Aged 23, Bell built a workshop in the new family home in Ontario and experimented there with converting music into an electrical signal.
In Boston, aged 25, Bell continued his experiments through the night while working in the day. In summer, he would return to his workshop in Ontario and continue his experiments.
Financial Backing for a Voice Telegraph
And now it was 1874, and Bell was The first electrical telegraph lines had been built forty years earlier, in the 1830s. These allowed electrical clicks (Morse code) to be instantly transmitted over great distances. Bell wanted to transmit human speech instead of clicks, and he was getting close to doing it.
He had found that human speech came in wave like patterns. He now hoped to produce an electrical wave that would follow the same patterns as someone’s speech.
And he won financial backing from Gardiner Hubbard and Thomas Sanders, two wealthy investors. Hubbard also brought in Anthony Pollok, his patent attorney.
The money enabled Bell to hire Thomas Watson, a skilled electrical engineer, whose knowledge would compliment Bell’s.
Patenting the Telephone
Aged 27, in 1875, Bell and his investors decided the time had come to protect his intellectual property using patents.
Alexander Graham Bell’s Telephone Patent. (Click to enlarge.)
Bell had a patent written for transmission of speech over an electrical wire. He applied for this patent in the UK, because in those days UK patents were granted only if they had not first been granted in another country. Bell told his attorney to apply in the USA only after the patent had been granted in the UK.
By 1876, things in the USA had become murkier. In February of that year, Elisha Gray applied for a US patent for a telephone which used a variable resistor based on a liquid: salt water.
In the transmitter, the liquid resistor transferred to an electric circuit the vibrations of a needle attached to a diaphragm which had been made to vibrate by sound. The electrical resistance of the circuit changed in tandem with the needle’s position in the liquid, and so sound was converted into an equivalent electrical signal. The receiver converted the electrical signal back into sound using a vibrating needle in liquid connected to a diaphragm which vibrated to recreate the sound that had been transmitted.
On the same day, Bell’s attorney filed his US patent application.
It was only in March 1876 that Bell actually got his invention to work, using a design similar to Gray’s. Hence Gray lay claim to have invented the telephone.
On the other hand, Bell had established the concept before Gray, and in all demonstrations of a working phone Bell gave or developed commercially he used his own setup rather than a water based variable resistor. In fact, in 1875, Bell had filed a patent for a liquid mercury based variable resistor, predating Gray’s liquid variable resistor patent.
Bell had to fend off around 600 lawsuits before he could finally rest in bed at night as the legally acknowledged inventor of the telephone.
“Mr. Watson, come here. I want to see you.”
The first words spoken in a telephone call: Alexander Graham Bell
Inventor
By summer 1876, Bell was transmitting telephone voice messages over a line several miles long in Ontario.
Making Money
Near the end of 1876, Bell and his investors offered to sell their patent to Western Union for $100,0Western Union ran America’s telegraph wires, and its top people believed the telephone was just a fad. They thought it would not be profitable.
How spectacularly wrong they were!
By 1878, Western Union’s opinion had altered dramatically. They now thought that if they could offer $25 million to get the patent, they would have gotten it cheaply.
Unfortunately for Western Union, in 1877, the Bell Telephone Company had been launched. And the rest, as they say, is history.
Not Just the Telephone
Alexander Graham Bell had a restless mind. The telephone made him wealthy and famous, but he wanted new challenges, and he continued inventing and innovating.
The Photophone, or Optical Telephone
Today, it is standard practice to transmit huge amounts of data using photons of light through optical fiber.
In 1880, Bell and his assistant Charles Summer Tainter transmitted wireless voice messages a distance of over 200 meters in Washington D.C. The voice messages were carried by a light beam, and Bell patented the photophone. This was two decades before the first radio messages were sent without wires and a century before optic fiber communications became commercially viable.
The receiver of Bell’s photophone. In Bell’s opinion, the photophone was his best invention.
The Metal Detector
In 1881, after President James Garfield was shot, Bell invented the metal detector to locate the bullet precisely. The rudimentary metal detector worked in tests, but the bullet in the President’s body was too deep to be detected by the early detecting equipment.
National Geographic Society
In 1888 Bell was one of the founders of the National Geographic Society. In 1897, he became its second president.
The End
Alexander Graham Bell died aged 75 on August 2, 1922 in Nova Scotia, Canada. He had been ill for some months with complications from diabetes. He was survived by his wife, Mabel, and two daughters – Elsie and Marian.
Every phone in North America was silenced during his funeral in his honor.
The unit of sound intensity, the bel, more usually seen as the smaller unit, the decibel, was named after Bell: it was conceived of in the Bell Laboratories.

Who is Alfred Wegener: Biography

Lived 1880 – 19
Alfred Wegener proposed the theory of continental drift – the idea that Earth’s continents move. Despite publishing a large body of compelling fossil and rock evidence for his theory between 1912 and 1929, it was rejected by most other scientists. It was only in the 1960s that continental drift finally became part of mainstream science.
Alfred Wegener: Beginnings
Alfred Wegener was born on November 1, 1880, in Germany’s capital city, Berlin.
His father, Richard Wegener, was a classical languages teacher and pastor. His mother, Anna Wegener, was a housewife. The Wegener family of two adults and five children – Alfred was the youngest – was quite well-off financially.
Alfred was an intelligent boy. He received a conventional education, attending grammar school in Berlin. His academic ability at school marked him clearly for a university education.
He began university in Berlin in 1899, aged 18, taking a variety of science classes, before specializing in astronomy, meteorology and physics.
In 1902 he began working towards a Ph.D. degree in astronomy, spending a year at Berlin’s famous Urania Observatory, whose purpose was, and still is, to bring astronomy to a wider public.
Alfred Wegener completed his astronomy Ph.D. in 1905, at the age of
Although he was now intellectually prepared to be a professional astronomer, he decided to abandon astronomy. He felt he might not discover anything new or interesting in astronomy. He believed he could make a greater contribution in meteorology – studying weather and climate.
Alfred Wegener’s Scientific Career
A first job and a world record
After completing his doctoral degree, Wegener started work in 1905 as a scientist at a meteorological station near the small German town of Beeskow.
There, working with his older brother Kurt, he carried out pioneering work with weather balloons studying air movements. If there had been a Guinness Book of World Records in 1906, the Wegener brothers would won a place for the longest continuous balloon flight ever: 52.5 hours in April of that year.
Greenland
Wegener was delighted to be appointed as the official meteorologist for the Danmark scientific expedition to the world’s largest island – Greenland, which took place from 1906 to 19The expedition’s principle aim was to chart the coastline of Greenland’s unexplored northeast coast. During the expedition, Wegener made his mark by building Greenland’s first meteorological station and taking a large number of atmospheric readings using kites and balloons.
The expedition’s work in uncharted territory was dangerous – three expedition members died of starvation/exposure!
University Lecturer
Back in Germany, in 1908, Wegener became an associate professor in meteorology at the University of Marburg. There he quickly gained a reputation for giving lectures that made difficult topics easy for his students to understand.
In 1910 he brought together the meteorological data he had gathered in Greenland with his talent for explaining tough concepts simply and published his first book: Thermodynamics of the Atmosphere.
He also had the first inkling of the idea that would bring him both anguish and long-lasting fame: continental drift.
Continental Drift
Wegener looks at a map and sits up
Looking at a world map in 1910, Wegener noticed how the coastlines of eastern South America and western Africa seemed to fit together, rather like jigsaw pieces.
The South American and African continents seem to fit quite well together.
Publishing fossil and geological evidence
After further research, he learned in 1911 that fossils of the same species could be found in Brazil and western Africa – evidence which seemed to indicate that South America and Africa had once been linked.
He researched geological data and found evidence of similar rock formations on the two continents.
In 1912, aged 32, Wegener gave talks at German universities and published two papers proposing that Earth’s continents moved.
A second expedition to Greenland followed by the outbreak of World War 1 (he was conscripted into the German Army) prevented Wegener making as much progress as he would have liked on his drift theory.
Nevertheless, while recovering from a wound in 1915, he wrote and published his groundbreaking book: The Origin of Continents and Oceans, discussing the movement of Earth’s continents.
He proposed that many millions of years ago Earth had consisted of a single great continent. Very slowly the land masses of this huge continent had moved apart to form the continents we see today.
Unfortunately, nobody took much notice!
Today we recognize that Wegener’s ancient continent actually existed. Its name is the one Wegener gave it – Pangaea.
From The Origin of Continents and Oceans: Alfred Wegener’s view of the supercontinent and superocean that existed on Earth about 300 million years ago. Color added by this website.
More evidence and more book editions
In 1920, 1922, and 1929 Wegener published updated editions of The Origin of Continents and Oceans, adding more evidence each time for his idea that the continents move around the planet at very slow speeds. He also added further evidence he had gathered in Greenland that it had once been linked to North America.
He pointed out that he was not the first person to propose the movement of continents; others had also found evidence from fossils and rocks which strongly suggested continents now far apart were once joined; the American geologist Frank Bursley Taylor had published evidence in 1910 supporting the idea of continental drift.
Wegener’s work was independent of Taylors; in 1920s America, people referred to continental drift as the Taylor-Wegener theory.
Wegener found that identical fossils could be found on different continents, supporting his theory that continents which are now far apart were once linked.
Geologists will not accept Wegener’s ideas
Scientists who stray into another field can encounter difficulties, such as those encountered by physicist Luis Alvarez when he proposed a meteor impact had resulted in the extinction of the dinosaurs.
Wegener, an astronomer who had become a meteorologist, encountered vigorous resistance to his ideas from a large majority of geologists.
In compiling a huge volume of convincing evidence for Pangaea and continental drift, he had made one or two small errors, and he also made one big error.
Although the rock and fossil evidence he reported should have been more than enough to convince skeptics that his theory was largely correct, Wegener tried to explain why continents move – and got this wrong!
Polflucht
Polflucht is German for pole flight. Wegener proposed that there was a geological force which pushed the continents away from Earth’s poles towards the equator. This was untrue.
Geologists told him it was untrue. Unfortunately they threw the baby out with the bathwater. They rejected Wegener’s truly compelling evidence for continental drift; they also rejected work which today we recognize as a forerunner of the correct explanation of continental drift – plate tectonics, the idea that solid continents float on a fluid mantle.
“It is a strange fact, characteristic of the incomplete state of our current knowledge, that totally opposite conclusions are drawn about prehistoric conditions on Earth, depending on whether the problem is approached from the biological or the geophysical viewpoint.”
Alfred Wegener
The Origin of Continents and Oceans
The End
Wegener published what would be the final edition of his book The Origin of Continents and Oceans in 19
On an unknown day in mid-November 1930, Alfred Wegener died at the age of 50 on his fourth expedition to Greenland.
He had been trying to resupply a remote camp in very bad weather. Temperatures had dropped as low as a deadly −60 °C (−76 °F).
He supplied the camp successfully, but there was not enough food at the camp for him to stay there. He and a colleague, Rasmus Villumsen, took dog sleds to travel to another camp.
Wegener died on this journey, probably of a heart attack. Villumsen buried Wegener’s body in the snow and marked the grave with skis. Villumsen then resumed his journey, but did not complete it. His body was never found.
Alfred Wegener (left) and Rasmus Villumsen on November 1 or 2, 19November 1 was Wegener’s fiftieth birthday.
In May 1931, after a search, Kurt Wegener discovered his brother’s grave. He and other expedition members built a pyramid-shaped mausoleum in the ice and snow, and Alfred Wegener’s body was laid to rest in it. The mausoleum has now, with the passing of time, been buried under Greenland’s ice and snow.
Alfred Wegener was survived by his wife, Else Köppen, whom he had married in 1913, and two daughters: Sophie Käte and Lotte.
“He was a person of flawless character, unadorned simplicity and rare modesty. At the same time, he was a man of action, who, in pursuing an ideal goal, achieved the extraordinary by means of his iron will power and tenacity while putting his life at risk.
Hans Benndorf, 1870 – 1953
Physicist and Seismologist
Alfred Wegener’s Scientific Legacy
Today, we recognize that continental drift theory is correct.
It was only in the 1960s, when the theory of plate tectonics was recognized as correct, that geologists finally accepted that Wegener’s continental drift theory and the concept of Pangaea were also correct. Wegener’s ideas are now standard concepts in geology, taught to everyone who studies the subject.

Who is Amedeo Avogadro: Biography

Lived 1776 – 18
Amedeo Avogadro is best known for his hypothesis that equal volumes of different gases contain an equal number of molecules, provided they are at the same temperature and pressure.
His hypothesis was rejected by other scientists. It only gained acceptance after his death. It is now called Avogadro’s law.
He was also the first scientist to realize that elements could exist in the form of molecules rather than as individual atoms.
Avogadro’s Life
Amedeo Avogadro was born in Turin, Italy, on August 9th, 17
His family background was aristocratic. His father, Filippo, was a magistrate and senator who had the title of Count. His mother was a noblewoman, Anna Vercellone of Biella.
Amedeo Avogadro inherited the title of Count from his father. In fact, Amedeo Avogadro’s full name was Count Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto – quite a mouthful!
Avogadro was highly intelligent. In 1796, when he was only 20, he was awarded a doctorate in canon law and began to practice as an ecclesiastical lawyer.
Although he had followed the family tradition by studying law, he gradually lost interest in legal matters. He found science was much more intellectually stimulating.
Mathematics and physics in particular attracted his logical mind. He spent increasing amounts of time studying these subjects. He was helped in this by the prominent mathematical physicist Professor Vassalli Eandi.
In 1803, in cooperation with his brother Felice, Avogadro published his first scientific paper, which looked at the electrical behavior of salt solutions. This was state-of-the-art science: only three years earlier, Avogadro’s fellow Italian scientist Alessandro Volta had demonstrated the electric battery for the first time.
In 1806, aged 30, Avogadro abandoned his successful legal practice and started teaching mathematics and physics at a high school in Turin. In 1809 he became a senior teacher at the College of Vercelli.
In 1820 Avogadro became the professor of mathematical physics at the University of Turin. Unfortunately, this post was short lived because of political turmoil. Avogadro lost his job in 18
Avogadro was reappointed in 1833 and remained in this post until, at the age of 74, he retired in 18
Although he was an aristocrat, Avogadro was a down-to-earth, private man, who was quietly religious. He was dedicated to hard work and his lifestyle was simple. His wife’s name was Felicita Mazzé. They married in 1818 when Avogadro was aged They had six sons.
Avogadro’s Contributions to Science
In the early 1800s, scientists’ ideas about the particles we now call atoms and molecules were very limited and often incorrect. Avogadro was deeply interested in finding out how the basic particles of matter behaved and came together to form chemical compounds.
He studied the work of two other scientists:
John Dalton
In 1808 John Dalton published his atomic theory proposing that all matter is made of atoms. He further stated that all atoms of an element are identical, and the atoms of different elements have different masses. In doing so, Dalton carried chemistry to a new level. But he also made mistakes about the way elements combine to form compounds. For example, he thought water was made of one hydrogen atom and one oxygen atom and wrote it as HO; today we know water contains two hydrogens to every oxygen and we write water as HActually, Avogadro figured this out, as we shall see.
Joseph Gay-Lussac
In 1809 Joseph Gay-Lussac published his law of combining gas volumes. He had noticed that when two liters of hydrogen gas react with one liter of oxygen gas, they form two liters of gaseous water. All gases that he reacted seemed to react in simple volume ratios.
Avogadro’s Hypothesis
In 1811 Avogadro published a paper in Journal de Physique, the French Journal of Physics. He said that the best explanation for Gay-Lussac’s observations of gas reactions was that equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules. This is now called Avogadro’s law. He published it when he was working as a physics teacher at the College of Vercelli.
In Avogadro’s (correct) view, the reason that two liters of hydrogen gas react with a liter of oxygen gas to form just two liters of gaseous water is that the volume decreases because the number of particles present decreases. Therefore the chemical reaction must be:
2H2 (gas) + O2 (gas) → 2H20 (gas)
In this reaction three particles (two hydrogen molecules and one oxygen molecule) come together to form two particles of water… or 200 particles react with 100 particles to form 200 particles… or 2 million particles react with 1 million particles to form 2 million particles… etc. The observable effect is that after the reaction, when all of the hydrogen and oxygen gases have become H20 gas, the volume of gas falls to two-thirds of the starting volume.
As a result of these observations Avogadro became the first scientist to realize that elements could exist as molecules rather than as individual atoms. For example, he recognized that the oxygen around us exists as a molecule in which two atoms of oxygen are linked.
Other scientists in the field, such as Dalton, believed that only compounds could form molecules while all elements existed as single atoms.
Avogadro realized that elements could exist in the form of molecules with individual atoms joined together.
In 1815 Avogadro published a further paper in Journal de Physique discussing the masses of atoms, their compounds and their gas densities.
In 1821, now writing as the professor of mathematical physics at the University of Turin, he published a further paper looking at the masses of atoms and the proportions in which they combine.
Between 1837 and 1841 Avogadro published four weighty volumes looking in detail at the physics of matter.
Avogadro’s findings were almost completely ignored until Stanislao Cannizarro presented them at the Karlsruhe Conference in 1860, four years after Avogadro’s death. This conference had been called to remedy the scientific confusion that existed about atoms, molecules and their masses.
Even after Cannizarro presented his work not all scientists agreed with it. Another decade passed – with continued strong advocacy from Cannizarro – before Avogardo’s hypothesis became more widely accepted and became Avogadro’s Law.
Today Avogadro is regarded as one of the founders of atomic-molecular chemistry.
Why Was Avogadro’s Hypothesis Rejected For Decades?
There are a number of reasons why Avogadro’s work was not accepted quickly:
• He published his work in Journal de Physique, which was not a very well read journal.
• The theories of better known scientists of the time, like John Dalton and Jöns Jacob Berzelius, disagreed with Avogadro’s work.
• Italy – the country of Leonardo da Vinci and Galileo – was no longer regarded as a country where great science was done. Realizing this, a few years earlier, Avogadro’s compatriot Alessandro Volta had traveled out of Italy to make himself and his work known to scientists in other countries. Avogadro stayed in Italy and did not make personal contact with foreign scientists to help bridge the gap as Volta had done.
Even though we like to think of science as a noble endeavor, where the truth will quickly become obvious, this is not always the case. Scientists are just people; they can be stubborn, just as we all can be at times. If you have a controversial new scientific theory, and you are not well-known, it seems that personal contact can sometimes achieve as much as a scientific paper – or even more.
Avogadro’s Constant
Avogadro’s constant is one of the most important numbers in chemistry. Its value is 6.02214129 x 10Avogadro did not calculate this number, but its existence follows logically from his hypothesis and work.
Avogadro’s constant is the number of particles (atoms or molecules) in one mole of any substance. For example, 12 grams of carbon contain 6.02214129 x 1023 carbon atoms.
Avogadro’s constant is an enormous number. If you could save a million dollars a second, it would take you longer than the universe is believed to have existed to save 6.02214129 x 1023 dollars; which all goes to show that it takes a lot of atoms to make a small amount of matter!
“My studies of the natural sciences have particularly involved that part of physics which looks at the atomic world: the properties of molecules, the forces involved in their movement, the heat capacity of different substances, expansion of gases by heat, and the density and pressure of gases.”
Amedeo Avogadro, 1776 – 1856
The End
Amedeo Avogadro died aged 79 on July 9th, 1856 in Turin. He was buried in the cemetery of Quaregna.

Who is Alfred Russel Wallace


Alfred Russel Wallace discovered the concept of evolution by natural selection.
Although he is now rarely mentioned as the discoverer (Darwin is usually cited) Wallace enjoyed a very high reputation in his lifetime, and was awarded many of the most prestigious awards in science.
He was a highly original thinker and was not afraid to court controversy. Few biologists would admit to believing that the spirits of dead people are around us, but Wallace did! He was also one of the first biologists to express concern about the effects humans were having on the natural world.
Early Life and Education
Alfred Wallace was born in Llanbadoc, Wales, 8 January, 18His family were middle class, but they were not well off. His father believed he was descended from William Wallace, the Scottish warrior portrayed in the movie Braveheart.
Alfred Wallace attended a grammar school: these schools did not charge fees and were attended by children who passed an academic selection test. Wallace had no formal training as a biologist and did not attend university. He trained and worked as a land surveyor, initially with his older brother’s firm.
Working outdoors, Wallace grew interested in the natural world and began collecting insects.
As his interest in insects grew, he became inspired reading about the work of naturalists such as Carl Linnaeus, Charles Darwin, and Alexander von Humboldt: these were scientists who had traveled overseas gathering samples, data, and discovering new species.
Wallace’s Travels
Brazil
To emulate his scientific heroes, in 1848, aged 25, Wallace embarked on a voyage to Brazil with the naturalist Henry Bates.
Wallace had little money and he intended to fund his work by collecting specimens in the Amazon for sale to British collectors and institutions. He also put his surveying skills to use, spending four years charting the course of the Rio Negro, collecting specimens, and making observations about the people and the languages he encountered along the way.
Wallace spent six years in Brazil before sailing back to the UK in 1852 with his collection of writings and specimens.
Unfortunately, the ship he was sailing on caught fire in the middle of the Atlantic Ocean. The passengers and crew abandoned ship and Wallace spent 10 days in an open boat before he was picked up. All the specimens he had brought on the ship were lost, along with most of what he had written and drawn.
Fortunately for Wallace, he had insured the specimens and he received money for their loss.
He now worked hard, writing six papers for academic journals and two books. He also spent time meeting and getting to know other British naturalists.
The East Indies
The unfortunate end to his Brazilian expedition did not diminish Wallace’s thirst for travel.
In 1854, aged 31, he set off on a new voyage: to Malaysia, Singapore, Indonesia and New Guinea.
This was a much more successful expedition than Brazil, and he discovered thousands of new species of beetle. He sent over 100,000 specimens of various species back to the UK.
He also observed how between two islands – Bali and Lombok – separated by a short stretch of water there was a big change in the animal life. This is now called the Wallace Line and marks a zone where Asian wildlife meets Australian wildlife.
The Wallace Line marks the zone where species from the Asian and Australian continents come together.
It was on this expedition that Wallace first described the theory of evolution.
Wallace returned to the UK from this expedition in 1862, aged
The Theory of Evolution by Natural Selection
Even before he embarked on his first voyage to Brazil, Wallace was interested in evolution, writing:
I should like to take some one family [of beetles] to study thoroughly, principally with a view to the theory of the origin of species.
On this first expedition he realized that geographical barriers often mark species boundaries.
On his second expedition, in the East Indies, he suffered a tropical fever which caused him to have hallucinations. When he recovered, he found that the theory of evolution by natural selection had come to him.
He wrote:
As animals usually breed much more quickly than does mankind, the destruction every year from these causes must be enormous in order to keep down the numbers of each species, since evidently they do not increase regularly from year to year, as otherwise the world would long ago have been crowded with those that breed most quickly. Vaguely thinking over the enormous and constant destruction which this implied, it occurred to me to ask the question, why do some die and some live? And the answer was clearly, on the whole the best fitted live… and considering the amount of individual variation that my experience as a collector had shown me to exist, then it followed that all the changes necessary for the adaptation of the species to the changing conditions would be brought about. In this way every part of an animal’s organization could be modified exactly as required, and in the very process of this modification the unmodified would die out, and thus the definite characters and the clear isolation of each new species would be explained.
And so the theory of evolution by natural selection was born.
As part of a continuing correspondence he was having with Charles Darwin, Wallace wrote a private letter to Darwin in June 1858 with an essay containing his theory of evolution.
Some people have suggested that Darwin stole Wallace’s idea. Sir Fred Hoyle, for example, proposed that although Darwin had a huge amount of data from the natural world, he had been unable to put it together into a satisfactory formulation.
Hoyle’s proposal is not supported by the majority of biologists and historians of science. Furthermore, Wallace and Darwin became friends. It seems unlikely a friendship would have been possible if Wallace believed Darwin had behaved badly to him.
When he received Wallace’s essay, Darwin passed it to the geologist Charles Lyell and botanist Joseph Hooker, with whom he had previously discussed his own ideas of evolution by natural selection. Lyell and Hooker decided Wallace and Darwin’s theories should be read at a meeting of the Linnean Society on July 1, 1858, and, to establish Darwin’s priority, which Lyell and Hooker believed was proper, Darwin’s should be read first.
An interesting question sometimes asked is: “How long would it have taken Darwin to publish his own theory of evolution, if Wallace hadn’t sent him that essay?”
Should it be Darwin’s or Wallace’s theory of Evolution
Today we hear about Darwin’s theory of evolution. In earlier times it was often called the Darwin-Wallace theory.
In 2002, recognizing Wallace’s discovery, the evolutionary biologist Richard Dawkins said that we should be talking about the Darwin/Wallace-mechanism of natural selection.
Awards
Wallace was one of the world’s greatest biologists. He received the highest awards science could bestow, including: Royal Medal (1868), Gold Medal of the Société de Géographie (1870), Darwin Medal (1890), Founder’s Medal (1892), Linnean Medal (1892), Copley Medal (1908), Gold Darwin-Wallace Medal (1908), Order of Merit (1908).
The End
Alfred Russel Wallace died aged 90 in Broadstone, England, 7 November, 19When he died, he was the most famous biologist in the world. Science historian George Beccaloni said of him:
“There were very long, glowing obituaries in all the world’s papers from Bombay to Boston saying he was the last of the great Victorians. One of the papers said only a great ruler would have had the sort of level of obituary recognition as Wallace.”

Who is Archimedes: Biography

Archimedes was, arguably, the world’s greatest scientist – certainly the greatest scientist of the classical age. He was a mathematician, physicist, astronomer, engineer, inventor, and weapons-designer. As we shall see, he was a man who was both of his time, and far ahead of his time.
Artists’ ideas of Archimedes. We do not know what he really looked like.
Archimedes was born in the Greek city-state of Syracuse on the island of Sicily in approximately 287 BC. His father, Phidias, was an astronomer.
Archimedes may also have been related to Hiero II, King of Syracuse.
Quick Guide – Archimedes’ Greatest Achievements
In the 3rd Century BC, Archimedes:
• invented the sciences of mechanics and hydrostatics.
• discovered the laws of levers and pulleys, which allow us to move heavy objects using small forces.
• invented one of the most fundamental concepts of physics – the center of gravity.
• calculated pi to the most precise value known. His upper limit for pi was the fraction 22⁄This value was still in use in the late 20th century, until electronic calculators finally laid it to rest.
• discovered and mathematically proved the formulas for the volume and surface area of a sphere.
• showed how exponents could be used to write bigger numbers than had ever been thought of before.
• proved that to multiply numbers written as exponents, the exponents should be added together.
• invented the Archimedean Screw to pull water out of the ground – the device is still used around the world.
• infuriated mathematicians who tried to replicate his discoveries 18 centuries later – they could not understand how Archimedes had achieved his results.
• directly inspired Galileo Galilei and Isaac Newton to investigate the mathematics of motion. Archimedes’ surviving works (tragically, many have been lost) finally made it into print in 15Leonardo da Vinci was lucky enough to have seen some of the hand-copied works of Archimedes before they were eventually printed.
• was one of the world’s first mathematical physicists, applying his advanced mathematics to the physical world.
• was the first person to apply lessons from physics – such as the law of the lever – to solve problems in pure mathematics.
• invented war machines such as a highly accurate catapult, which stopped the Romans conquering Syracuse for years. It’s now believed he may have done this by understanding the mathematics of projectile trajectory.
• became famous throughout the ancient world for his brilliant mind – so famous that we cannot be sure that everything he is said to have done is true.
• inspired what we now believe are myths including a mirror system to burn attacking ships using the sun’s rays, and jumping from his bath, and running naked through the streets of Syracuse shouting ‘Eureka’ meaning ‘I’ve found it’ after realizing how to prove whether the king’s gold crown had silver in it.
Early Days and Greek Culture
The ancient Greeks were the first people to do real science and recognize science as a discipline to pursue for its own sake.
Although other cultures had made scientific discoveries, these were made for thoroughly practical reasons, such as how to build stronger temples or predict when the heavens would be right for planting crops or getting married.
Today, we’d describe much of the Ancient Greeks’ work as blue skies scientific research.
They investigated the world for the sheer pleasure of adding to their knowledge. They studied geometry for its logic and its beauty. With no practical purpose in mind, Democritus proposed that all matter was made of tiny particles called atoms and that these atoms could not be split into smaller particles. He produced logical arguments for his idea.
Archimedes was born into this Greek scientific culture. He must have felt the influence particularly strongly, flowing from his astronomer father. We believe his father was an astronomer, because Archimedes tells us in his work The Sand Reckoner. Writing about another astronomer’s estimates of the sun’s size, he says: “Pheidias, my father, said the sun was twelve times bigger.”
Archimedes spent most of his life in Syracuse. As a young man, he furthered his education in the city of Alexandria in Egypt, where Alexander the Great’s successor, Ptolemy Lagides, had built the world’s greatest library.
The Library of Alexandria, with its meeting rooms and lecture halls, had become the focal point for scholars in the ancient world.
Some of Archimedes’ work is preserved in copies of the letters he sent from Syracuse to his friend Eratosthenes. Eratosthenes was in charge of the Library of Alexandria, and was no mean scientist himself. He was the first person to calculate the size of our planet accurately.
An artist’s view of Archimedes’ friend Eratosthenes teaching in the Library of Alexandria. Of course, the books in the library would have been scrolls, rather than the codex style shown here.
Immersed in the scientific culture of Ancient Greece, Archimedes blossomed into one of the finest minds our world has known. He was the Einstein of his time, or perhaps we should say that Einstein was the Archimedes of his time.
An Annoying Mathematician Ignites Curiosity Far into the Future
Two thousand years after Archimedes’ time, during the Renaissance and 1600s, mathematicians looked again at his work.
They knew Archimedes’ results were correct, but they couldn’t figure out how the great man had found them.
Archimedes was very frustrating, because he gave clues, but did not reveal his full methods. In truth, Archimedes enjoyed teasing other mathematicians, such as Eratosthenes. He would tell them the correct answer to problems, then see if they could solve the problems for themselves.
1800 years later, annoyed that they could not figure out what Archimedes had done long in the past, Renaissance mathematicians pushed themselves to greater heights, carrying out new research, trying to measure up to Archimedes.
A Real Life Indiana Jones Style Discovery
The mystery of Archimedes’ mathematics wasn’t solved until 1906, when Professor Johan Heiberg discovered a book in the city of Constantinople, Turkey. (The city is now, of course, called Istanbul.)
The book was a Christian prayer book written in the thirteenth century, when Constantinople was the last outpost of the Roman Empire. Within Constantinople’s walls were stored many of the great works of Ancient Greece. The book Heiberg found is now called the Archimedes Palimpsest.
Heiberg discovered that the book’s prayers had been written on recycled vellum. The vellum had originally been home to what looked like mathematics. The monks who wrote the prayers had tried to remove the original mathematical work, and only faint traces remained of it.
It turned out that the traces of mathematics were actually copies of Archimedes’ work – a momentous discovery. The Archimedes text had been copied on to the vellum in the 10th century.
A false color view of a page from the Archimedes Palimpsest, showing some of the recovered mathematics. Courtesy of The Walters Museum.
Archimedes Revealed
There were seven treatises from Archimedes in the book including The Method, which had been lost for many, many centuries.
Archimedes had written The Method to reveal how he did mathematics. He’d sent it to Eratosthenes to be lodged in the Library of Alexandria. Archimedes wrote:
“I presume there will be some current as well as future generations who can use The Method to find theorems which we have not discovered.”
And so we learned just how far ahead of his time Archimedes’ math had been: using summing of series; using his law of the lever to establish how theoretical mathematical objects would behave; and using infinitesimals to do work as close to integral calculus as anyone would get until Newton finally got there 1800 years later.
Archimedes’ Famous Discoveries and Inventions
The Archimedes’ Screw
One of Archimedes’ marvelous inventions is the ‘Archimedean Screw.’ This device is rather like a corkscrew within an empty tube. When the screw turns, water is pulled up the tube, so the screw can pull water up from a river, lake, or well.
The Archimedes’ Screw
Archimedes is thought to have invented this device when he was in Egypt, where it’s still used for irrigation. It’s also helpful for lifting light, loose materials such as ash, grain, sand from a lower level to a higher level and is still used worldwide for a variety of purposes.
The Story of the Golden Crown
King Hiero II had given gold to a craftsman to make him a crown. The crown he got back weighed the same as the gold given to the craftsman, but King Hiero was suspicious. He thought the craftsman had stolen some gold, replacing it with silver in the crown. He couldn’t be sure, so he sent for Archimedes and explained the problem to him.
It was known that gold was denser than silver, so a one centimeter cube of gold would weigh more than a one centimeter cube of silver.
The problem was that the crown was irregularly shaped, so although its weight was known, its volume wasn’t.
Archimedes is believed to have measured how much the level of water in a cup was raised by sinking, for example, one kilogram of gold in it, and comparing this with one kilogram of silver.
If we did this measurement using modern equipment, we would find the 1 kg of gold would raise the water level by 51.8 ml and the 1 kg of silver by 95.3 ml.
So, if King Hiero’s crown weighed 1 kg, and it raised the water level by 52 ml or so, then the crown would be pure gold. If the water level rose more than this, then some of the gold had been replaced by silver.
Archimedes found that the crown was a mixture of gold and silver, which was bad news for King Hiero, and even worse news for the King’s craftsman!
Archimedes is supposed to have had the idea of how to solve King Hiero’s problem when he was taking a bath, noticing the water level moving as he lowered and raised himself. He was so excited that he leaped up and ran naked through the streets of Syracuse shouting ‘Eureka,’ meaning, ‘I’ve found it.’ It seems that even thousands of years ago, scientists had a reputation for being a little crazy!
Calculation of Pi
π is the number you get when you divide the circumference of a circle by its diameter.
To calculate a circle’s area, or circumference, you need to know π.
Archimedes was intensely interested in calculating the mathematical properties of curved solids, such as cylinders, spheres and cones. To do this, he wanted to learn more about π.
We now know that π is an irrational number: 3.14159265358979… the numbers after the decimal point never end, so an exact value can never be found.
Archimedes knew that the circumference of a circle equals 2 x π x r, where r is the circle’s radius.
Here is how Archimedes calculated the circumference of a circle of known radius, and hence found π.
He imagined a circle, and in his mind drew an equilateral triangle inside it, with each point of the triangle touching the circle. Outside the circle, he drew another equilateral triangle, with each side touching the circle.
Archimedes drew a mental image of a circle bounded by triangles.
He could easily calculate the perimeter of each triangle, and therefore he knew the circle’s circumference was greater than the inside triangle and smaller than the outside triangle.
Then, using a formula he had devised to calculate the perimeter of a polygon with double the number of sides of the previous polygon, he repeated his calculation, this time for a circle with a regular hexagon inside it, and a regular hexagon outside it. The hexagons enclosed the circle more closely than the triangles had and their perimeters were nearer to the true circumference of the circle.
Archimedes drew a mental image of a circle bounded by regular hexagons.
In this way Archimedes tightened the limits for the maximum and minimum circumference of the circle.
Next, he imagined a circle between two 12-sided regular polygons, then two 24-sided regular polygons, then two 48-sided regular polygons. Finally, Archimedes calculated the circumference of a 96-sided regular polygon inside his circle, and a 96-sided regular polygon outside his circle.
A 96-sided regular polygon looks the same as a circle unless you zoom in with high magnification.
Is this a polygon, or a circle?
Above is a 90-sided polygon. It has fewer sides than the 96-sided polygon Archimedes used for his calculation, but you can see that it looks like a circle to the human eye.
Using the 96-sided polygon, Archimedes found that π was greater than the fraction 25344⁄8069, and less than the fraction 29376⁄93
For the world at large, he simplified these numbers, losing a tiny amount of precision to say π was bigger than 310⁄71 and smaller than 31⁄
If we average Archimedes’ best upper and lower limits for π, we get it to be 3.141868115 to nine decimal places. Archimedes’ value of π differs from the value on your calculator by less than 1 part in 10,0
In fact, Archimedes’ value of π of 31⁄7 (this is often written as 22⁄7) was used until it became less necessary in our digital age.
Remember that Archimedes did not actually make measurements for his calculations. They could never have been precise enough. He used pure mind-power to calculate the areas involved in each situation.
Calculation of the Volume of a Sphere
Archimedes saw his proof of the volume of a sphere as his greatest personal achievement. His work is remarkable for its similarity to modern calculus.
Archimedes gave instructions that his proof should be remembered on his gravestone.
The Beast Number
Read about how Archimedes invented the Beast Number, a number so enormous that the visible universe isn’t big enough to write it out in full.
And all this because he was fed up of people saying that it was impossible to calculate how many grains of sand there were on a beach.
Death and Legacy
Archimedes died during the conquest of Syracuse in 212 BC when he was killed by a Roman soldier.
Cicero at Archimedes’ Tomb. Painting by
Benjamin West
He was buried in a tomb on which was carved a sphere within a cylinder. This was his wish, because he believed his greatest achievement was finding the formula for the volume of a sphere.
Many years later, Cicero, the Roman Governor of Sicily, went looking for the tomb of Archimedes.
He found that it had become overgrown with weeds and bushes, which he ordered to be cleared.
Today, we do not know where Archimedes’ tomb is – it has been lost, probably for ever.
Much of his work has also been lost for ever, but what we know of it leaves us in awe of his achievements from so long ago.
More than 300 years after Archimedes’ death, the Greek historian Plutarch said of him:
“He placed his whole affection and ambition in those purer speculations where there can be no reference to the vulgar needs of life.”
Archimedes was a great practical scientist, but above all, he lived up to the Greek ethos of carrying out blue sky research. He worked on mathematical problems for the sake of mathematics itself, not to solve practical problems. Funnily enough, all of his discoveries in mathematics ultimately did prove to be useful both practically as well as mathematically.
On his tomb, in addition to the sphere in the cylinder, his name was written in Greek:
ΑΡΧΙΜΗΔΗΣ

Who is Aristarchus: Biography

Aristarchus It’s funny, but not all of the scientists we talk about on this website are actually famous. Some of them, like Aristarchus, deserve to be… but they’re not.
An artist’s view of how Aristarchus might have looked.
If you’re looking for an unsung hero of science, you could do worse than Aristarchus of Samos, or Aristarchus the Mathematician as some people called him. Today, a better name might be Aristarchus, who discovered that Earth orbits the Sun.
Aristarchus was born in about the year 310 BC, probably on the Greek island of Samos, the same island that Pythagoras had been born on 260 years earlier. We know very little about Aristarchus’s life, but we know enough to be astounded by his science.
We know that Aristarchus lived at about the same time as two of our other scientific heroes, Archimedes and Eratosthenes, and that he was 20 to 30 years older than them. We know that his greatest work has been lost in the mists of time. We know a little about this work because Archimedes mentions it in a work called The Sand Reckoner, more of which soon.
Copernicus says that Earth orbits the Sun
To appreciate what Aristarchus did over 2000 years ago, it’s worthwhile thinking about one of the greats of astronomy, Nicolaus Copernicus.
In 1543 Nicolaus Copernicus published his famous book: On the Revolutions of the Heavenly Spheres. He told us that Earth, and all the other planets, orbit the sun. In other words, he said that the Solar System is heliocentric.
Until Copernicus published his work, people thought we lived in a geocentric Solar System – i.e. that Earth was at the center of everything. They believed that the moon, the planets, the sun and the stars orbited the earth.
The geocentric idea was taught by the Catholic Church, and Copernicus was a member of that church. Copernicus’s book was suppressed by the church, but gradually, his theory came to be accepted.
In fact, however, Copernicus was rather late coming to the heliocentric view.
Aristarchus beat him by 18 centuries.
Archimedes tells us about Aristarchus’s Book
Sadly, the book Aristarchus wrote describing his heliocentric Solar System has been lost – the fate of many great Ancient Greek works. Fortunately, we know a little about it, because it is mentioned by other Greeks, including Archimedes, who mentions it in a letter he addressed to a King named Gelon. This letter was ‘The Sand Reckoner.’ Archimedes wrote:
“You know the universe is the name astronomers call the sphere whose radius is the straight line from the center of the earth to the center of the sun. But Aristarchus has written a book in which he says that the universe is many times bigger than we thought. He says that the stars and the sun don’t move, and that the earth revolves about the sun and that the path of the orbit is circular.”
Aristarchus must have used the concept of parallax to show that the stars are a very large distance from Earth. In doing so, he expanded the size of the universe enormously.
It would be marvelous if we could learn the details of Aristarchus’s observations, calculations, arguments, could read his notes and see his diagrams; but, unless a copy of his ancient book can be discovered in some forgotten, dusty corner of an ancient library, that is a pleasure we shall never have.
A modern view of the bodies orbiting in our heliocentric Solar System. Aristarchus would have been thrilled to know what we know now. Image credit: NASA/JPL-Caltech (click for larger image).
Aristarchus also believed that, in addition to orbiting the sun, Earth was spinning on its own axis, taking one day to complete one revolution.
Aristarchus Offends the ‘Pious’
Unfortunately, it seems that Aristarchus’s idea didn’t find many fans. In fact, echoing the persecution of Renaissance scientists, some Greeks wanted to put Aristarchus on trial for daring to say Earth was not at the center of the universe. Most Ancient Greeks rejected Aristarchus’s work, and continued to believe in a geocentric Solar System.
Thankfully, Archimedes was happy to use Aristarchus’s model of the universe in The Sand Reckoner, to discuss calculations using larger numbers than the Greeks had used before.
Only one of Aristarchus’s works has survived, in which he tried to calculate the sizes of the moon and sun and tried to figure out how far they were from Earth. He already knew the sun was much larger than Earth by observing Earth’s shadow on the moon during a lunar eclipse, and he also knew that the sun was much farther away from us than the moon.
Although the optical technology of his time didn’t allow Aristarchus to know the finer details of our Solar System, his deductions were absolutely correct based on what he could actually see. What he lacked in technology, he made up for in deductive genius.
What Aristarchus got Right
23 centuries ago, Aristarchus’s proposed, with evidence, that the earth and the planets orbit the sun. He further deduced that the stars are much farther away than anyone else had imagined, and hence that the universe is much bigger than previously imagined. These were major advances in human ideas about the universe.
What did Copernicus know about Aristarchus’s Work?
Copernicus actually acknowledged in the draft of his own book that Aristarchus might have said the earth moved around the sun. He removed this acknowledgement before he published his work.
In Copernicus’s defense, he was probably unaware of The Sand Reckoner by Archimedes, because, after its rediscovery in the Renaissance, The Sand Reckoner only seems to have existed as a few hand-written copies until it was finally printed in 15By then Copernicus had published his own book and had died. What he knew of Aristarchus probably came from the following very brief words written by Aetius:
“Aristarchus counts the sun among the fixed stars; he has the earth moving around the ecliptic [orbiting the sun] and therefore by its inclinations he wants the sun to be shadowed.”
Galileo knew that Aristarchus was the First Heliocentrist
Galileo Galilei, who most certainly had read The Sand Reckoner, and understood its message, did not acknowledge Copernicus as the discoverer of the heliocentric Solar System. Instead, he described him as the ‘restorer and confirmer’ of the hypothesis.
Clearly, Galileo reserved the word ‘discoverer’ for Aristarchus of Samos.
Aristarchus lived for about 80 years. If we could have built on his insights, rather than forgetting about them for so many centuries, I wonder how much further we might have come in our understanding the Universe.

Who is Benjamin Franklin: Biography

Lived 1706 – 17
Benjamin Franklin lived his life in the spirit of a renaissance man: he was deeply interested in the world around him, and he excelled in several widely differing fields of human endeavor.
He had a profound effect on our understanding of electricity and shaped the language we use when we talk about it, even today.
Here we shall concentrate on his life as a scientist and an inventor, only briefly touching on his other achievements.
Benjamin Franklin’s Early Life and Education
Benjamin Franklin was born on January 17, 1706, in Boston, Massachusetts. His father, Josiah, was a tallow chandler, candle maker, and soap boiler who had moved to the American Colonies from England. His mother, Abiah Folger looked after the home and was the mother of ten children, including Benjamin, who was the eighth child in the family. She was born in Nantucket, Massachusetts.
Benjamin only had two years of formal education, which finished when he was ten years old, because his family could not afford the fees. His informal education then accelerated, because his mind was too restless to stop learning.
He had to work in his father’s business, but in his spare time he read everything he could, about every subject under the sun.
When he was twelve, Benjamin began working as an apprentice in a printing shop owned by one of his elder brothers, James. When his brother started printing a newspaper, Benjamin wrote to it in the name of “Mrs. Dogood” in defense of freedom of speech.
Aged 17, Benjamin Franklin left for Philadelphia, escaping from his apprenticeship, which was against the law. He was, however, free. After a few months in Philadelphia he left for London, England, where he learned more about printing, before returning to Philadelphia at the age of 20 to continue his career in printing.
Benjamin Franklin – Publisher
By the age of just 23, Franklin had become the publisher of the Philadelphia Gazette.
Aged 27, in December 1732, the first editions of the publication that would make him a wealthy man rolled off his printing press: Poor Richard’s Almanac, which Franklin would publish annually for the next 25 years. It was a general interest pamphlet offering interest and amusement for its readers, including: ‘how to’ guides, practical tips, stories, astrological forecasts, and brain teasers.
With each year he published the Almanac, his financial position grew more secure, and Franklin’s fertile mind began looking for new outlets.
He continued reading as much as he could, increasing his knowledge of science and technology until he was in a position to begin innovating himself.
Benjamin Franklin’s Science, Innovation, and Inventions
Franklin was an original thinker, scientist and inventor. Dating his inventions is not always easy, because Franklin did not patent what he invented. He said that anyone who wanted to make money from his ideas was free to do so. This means the dates given to his inventions are approximate.
Bifocal Spectacles
Franklin wore spectacles for most of his life.
He felt limited by the spectacles of his day, because a lens that was good for reading blurred his vision when he looked up. Working as a printer, this could be infuriating.
He defeated this problem in about 1739, aged 33, with his invention of split-lens bifocal spectacles. Each lens now had two focusing distances. Looking through the bottom part of the lens was good for reading, while looking through the upper part offered good vision at a greater distance.
The Franklin Stove
As Franklin read more about science, he learned more about heat transfer. He looked at the design of a typical stove and concluded that it was inefficient. Much more heat was lost up the flue than necessary.
He decided to redesign the stove using the concept of heat-exchange/heat recovery.
The idea was that hot gases which would normally simply go up the flue would exchange their heat with cold air from the room, heating it up, and so heating the room up.
In 1741, the Franklin Stove came on to the market, allowing homeowners to get more heat into their homes for each unit of fuel they burned.
Cold air (blue) gains heat from contact with the hot stove. As this warming air continues on its path, it gains more heat through contact with metal, the other side of which is in contact with the hot smoke (red) going to the flue.
Franklin wrote:
The use of these fireplaces in very many houses, both of this and the neighboring colonies, has been, and is, a great saving of wood to the inhabitants.
American Philosophical Society
In 1743, Franklin founded the American Philosophical Society. (In those days, scientists were called philosophers.) The Society offered a scientific forum for new ideas, including Franklin’s electrical theories.
The Size of the Units of Matter
Benjamin Franklin performed a beautiful experiment using surfactants; on a pond at Clapham Common, he poured a small amount of oleic acid, a natural surfactant which tends to form a dense film at the water-air interface. He measured the volume required to cover all the pond. Knowing the area, he then knew the height of the film, something like three nanometers in our current units.
Pierre-Gilles de Gennes, 1932 to 2007
Electricity
In summer 1743, Franklin visited his hometown of Boston. Always seeking new knowledge, he visited a science show. There he saw Dr. Archibald Spencer, who had arrived from Scotland, demonstrating a variety of scientific phenomena. The electrical part of the show intrigued Franklin most: it featured the effects of static electricity.
Franklin left the show determined to learn more about electricity. It seemed to him that Dr. Spencer didn’t really understand it. This, of course, was true: nobody understood it! It was more a source of entertainment than a science.
In 1747, Franklin got hold of a long glass tube for the efficient generation of static electricity from Peter Collinsion in London.
Soon, Franklin was spending much of his time studying electricity. He wrote:
“For my own part, I never was before engaged in any study that so totally engrossed my attention and my time as this has lately done.”
Shaping our understanding of electricity
Franklin’s observations soon began to shape the world’s understanding of electricity and shape the language we use even today when we talk about it.
He identified that there was an electrical fluid that could flow from A to B. To describe the process he coined the terms positive and negative to describe the difference between A and B after the electrical fluid had flowed. Of course, today we would call the electrical fluid electrons, but remember: this was 1747; J.J. Thomson’s discovery of the electron lay 150 years in the future!
Franklin found that an excess of fluid led to positive charge (okay, we’ll have to pretend that electrons are positively charged for this) and a deficit of fluid led to negative charge.
Franklin was the first to write that electric charge cannot be created; it can only be ‘collected.’ This is a fundamental law of physics – the Law of Conservation of Electric Charge. It means that you cannot create (or destroy) electric charge.
Franklin was also the first person to use the words electrical battery. His meaning was not the same as ours though. His battery was made of capacitors (known as Leyden jars) wired together in series to store more charge than one alone could. This enabled Franklin to produce a bigger discharge of static electricity in his experiments.
In 1751, Franklin published the fruits of his labors in a book called Experiments and Observations on Electricity, which was widely read in Britain and then Europe, shaping a new understanding of electricity.
In 1752 Franklin’s most famous scientific work was carried out – the proof that lightning is electricity.
Franklin had an idea for an experiment to prove that lightning is electricity, making use of another of his own discoveries in electricity: that static electricity discharges to a sharp, pointed object more readily than to a blunt object.
And now here are Benjamin Franklin’s own words on the subject:
From Benjamin Franklin’s Experiments and Observations on Electricity
Benjamin Franklin
“As electrified clouds pass over a country, high hills and high trees, lofty towers, spires, masts of ships, chimneys, etc, as so many prominences and points, draw the electrical fire, and the whole cloud discharges there…
“If these things are so, may not the power of points be of use to mankind, in preserving houses, churches,… from the stroke of lightning, by directing us to fix on the highest parts of those edifices, upright rods of iron made sharp as a needle… and from the foot of those rods a wire down the outside of the building into the ground…?
Benjamin Franklin’s Proposed Sentry Box
“I would propose an experiment… On the top of some high tower or steeple, place a kind of sentry-box big enough to contain a man and an electrical stand. From the middle of the stand, let an iron rod rise and pass bending out of the door, and then upright 20 or 30 feet, pointed very sharp at the end. If the electrical stand be kept clean and dry, a man standing on it when such clouds are passing low might be electrified and afford sparks, the rod drawing fire to him from a cloud. If any danger to the man should be apprehended (although I think there would be none) let him stand on the floor of his box, and now and then bring near to the rod a loop of wire that has one end fastened to the leads he his holding by a wax handle; so the sparks, if the rod is electrified, will strike from the rod to the wire and not affect him.”
King Louis XV saw a translation of Experiments and Observations on Electricity, and he asked French scientists to test Franklin’s lightning rod concept.
Jean Francois Dalibard used Franklin’s idea to confirm by experiment that lightning was indeed electrical in Paris in May 17Franklin himself carried out similar work in 1752, using a kite with a metal key connected to a Leyden Jar to prove his own theory. He didn’t write about his own experiment, however, until 17
The significance of the experiment was that it established the study of electricity as a serious scientific discipline.
Franklin had shown how to prove that electrical phenomena were a fundamental force of nature. Electricity would never again be thought of as just an interesting plaything for scientists and showmen to conjure up using glass rods.
Very soon, in 1753, when he was aged 47, the transformation in science that Franklin had brought about was recognized. Britain’s Royal Society honored his electrical work with its highest award, the Copley Medal – the equivalent of a modern Nobel Prize.
The Lightning Rod
A building protected by a lightning rod. A cable carries electricity from lightning to ground.
Even today, we still use Benjamin Franklin’s lightning rod.
Like his other ideas, he did not patent it: he profited from the lightning rod intellectually, not financially.
Since the time he invented it, it has saved societies all over the world great amounts of time and money by protecting buildings from damage. It has also, of course, saved countless lives.
Refrigeration
In 1758, working with John Hadley in Cambridge, England, Franklin investigated the principle of refrigeration by evaporation.
In a room at 18 °C (65 °F) , the scientists repeatedly wetted a thermometer with ether, then used bellows to quickly evaporate the ether.
They were finally able to achieve a temperature reading on the thermometer of -14 °C (7 °F).
We now know the reason for the refrigeration effect. We have learned that molecules in a liquid have a range of energies. Some have high energy, and some have low energy. Molecules carrying the most energy escape from the liquid most easily – they evaporate. This leaves the lower energy, colder molecules in the liquid. The result is that the temperature of the liquid falls.
Of his discovery, Franklin said:
“One may see the possibility of freezing a man to death on a warm summer’s day.”
In fact, the principle of cooling by evaporation had been publicly demonstrated by William Cullen in Edinburgh, Scotland in 17Cullen had used a pump to lower the pressure above ether in a container.
The reduced pressure caused the ether to evaporate rapidly through boiling, absorbing heat from the air around it, and causing some ice to form on the container sides.
Meteorology
By observation of storms and winds, Franklin discovered that storms do not always travel in the direction of the prevailing wind. This was an important discovery in the development of the scientific discipline of meteorology.
More than a Scientist and Inventor
Franklin lived in turbulent times, which culminated in the United States’ Declaration of Independence in 1776: Franklin was one of the five men who drafted it. He had previously acted as British postmaster for the colonies; he was the American Ambassador in France from 1776 – 1785; and the governor of Pennsylvania from 1785 – 17
The End
Benjamin Franklin died on April 17, 1790, at the age of He was killed by pleurisy – a lung inflammation.
His wife, Deborah, had died sixteen years earlier. Franklin was survived by his daughter, Sarah, who looked after him in his later years and his son, William. William left America to live in Britain in 17
Today, the Benjamin Franklin Medal, named in Franklin’s honor, is one of the most prestigious awards in science. Its winners include Alexander Graham Bell, Marie and Pierre Curie, Albert Einstein and Stephen Hawking.

Who is Brahmagupta: Biography

Brahmagupta is unique. He is the only scientist we have to thank for discovering precisely zero…
Brahmagupta was an Ancient Indian astronomer and mathematician, who lived from 597 AD to 668 AD. He was born in the city of Bhinmal in Northwest India. His father, whose name was Jisnugupta, was an astrologer.
Although Brahmagupta thought of himself as an astronomer who did some mathematics, he is now mainly remembered for his contributions to mathematics.
Many of his important discoveries were written as poetry rather than as mathematical equations! Nevertheless, truth is truth, regardless of how it may be written.
Quick Guide to Brahmagupta
Brahmagupta:
• was the director of the astronomical observatory of Ujjain, the center of Ancient Indian mathematical astronomy.
• wrote four books about astronomy and mathematics, the most famous of which is Brahma-sphuta-siddhanta ( Brahma’s Correct System of Astronomy, or The Opening of the Universe.)
• wrote that solving mathematical problems was something he did for pleasure.
• was the first person in history to see zero as a number with its own properties.
• defined zero as the number you get when you subtract a number from itself. Identifying zero as a number whose properties needed to be defined was vital for the future of mathematics and science.
• said that zero divided by any other number is zero.
• said that dividing zero by zero produces zero. (Although, this seems reasonable, Brahmagupta actually got this one wrong. Mathematicians have now shown that zero divided by zero is undefined – it has no meaning. There really is no answer to zero divided by zero.)
• was the first person to discover the formula for solving quadratic equations.
• wrote that pi, the ratio of a circle’s circumference to its diameter, could usually be taken to be 3, but if accuracy were needed, then the square-root of 10 (this equals 3.162…) should be used. This is about 0.66 percent higher than the true value of pi.
• indicated that Earth was nearer the moon than the sun
• incorrectly said that Earth did not spin and that Earth did not orbit the sun. This, however, may have been for reasons of self-preservation. Opposing the Brahmins’ religious myths of the time would have been dangerous.
• produced a formula to find the area of any four-sided shape whose corners touch the inside of a circle. This actually simplifies to Heron’s formula for triangles.
• wrote that the length of a year was 365 days 6 hours 12 minutes 9 seconds.
• calculated that Earth was a sphere of circumference around 36,000 km (22,500 miles).
Brahmagupta established rules for working with positive and negative numbers, such as:
• adding two negative numbers together always results in a negative number.
• subtracting a negative number from a positive number is the same as adding the two numbers.
• multiplying two negative numbers together is the same as multiplying two positive numbers.
• dividing a positive number by a negative, or a negative number by a positive results in a negative number.
Why is Zero Important?
Although it may seem obvious to us now that zero is a number, and obvious that we can produce it by subtracting a number from itself, and that dividing zero by another non-zero number gives an answer of zero, these results are not actually obvious.
The brilliant mathematicians of Ancient Greece, so far ahead of their time in many ways, had not been able to make this breakthrough. Neither had anyone else, until Brahmagupta came along!
It was a huge conceptual leap to see that zero was a number in its own right. Once this leap had been made, mathematics and science could make progress that would have been impossible otherwise.
Brahmagupta might smile at the fact that, without his concept of zero, we would not have the science of thermodynamics; and without thermodynamics we could not even begin to understand the universe – the same universe that Brahmagupta, who viewed himself chiefly as an astronomer, tried so hard to understand over 1300 years ago.

Who is Carolus Linnaeus: Biography

1707 – 1778
Carolus Linnaeus is one of the giants of natural science. He devised the formal two-part naming system we use to classify all lifeforms.
A well-known example of his two-part system is the dinosaur Tyrannosaurus rex; another is our own species – Homo sapiens.
In fact, Linnaeus pushed the science of biology to new heights by describing and classifying our own human species in precisely the same way as he classified other lifeforms. Other people at that time demanded that humans must be regarded as a special case in biology, different from animals.
Early Life and Education
Carl Linnaeus was born on May 23, 1707 in the village of Råshult in southern Sweden. His father was Nils Ingemarsson Linnaeus, a church minister and amateur botanist; and his mother was Christina Brodersonia.
His father believed that the best thing he could offer his children was a solid education and, in addition to botany, taught Carl about religion and to speak Latin before the young boy could walk.
Carl paid close attention to his father’s activities. He soon picked up his father’s love of plants and botany; he began growing his own plants in his family’s generously sized garden and walking further afield, searching for new plants.
His father recognized that Carl had a good mind. To improve his education he brought in a private tutor when the boy was seven.
In comparison with lessons given by his father, and his days in the garden and countryside cultivating and searching for plants, Carl found the tutor’s work very dull.
Carl Linnaeus started school at the age of He was not a bad student, but he did not excel. He continued to work hard on his own private botanical studies.
By the end of his secondary schooling, his teachers had formed the opinion that he was not bright enough to go to university. His immense interest in and knowledge of botany were ignored – it was not a ‘proper subject.’ His teachers expected their students to be skilful in Greek, Hebrew, mathematics and theology, but Carl was not especially interested in these subjects.
Fortunately, one of his school teachers, Johan Rothman, who was also a medical doctor, recognized the boy’s talents and advised his father that Carl should aim for a career in medicine. Carl moved into the Rothman family home, where Rothman gave him formal lessons in anatomy and physiology as well as botany.
By the age of 21, Linnaeus was ready for university.
He enrolled at Lund University using the Latin form of his name, Carolus Linnaeus. This was common practice for students in Europe. For example, centuries earlier, when Mikolaj Kopernik enrolled at university in Poland, he took the Latin name Nicolaus Copernicus.
After just one year at Lund University, Linnaeus switched to Uppsala University, because Rothman told him the medicine and botany courses were better at Uppsala. This proved to be untrue, but actually worked out well for Linnaeus.
After studying at Uppsala for a year, Linnaeus wrote up some of his thoughts and observations on reproduction in plants. One of Uppsala’s medical professors, Olof Rudbeck, read what Linnaeus had written.
The courses at Uppsala were so bad that Rudbeck formed the view that the second year student Linnaeus knew more about botany than the lecturers! In 1730, aged just 23, Linnaeus became a botany lecturer at Uppsala University. He turned out to be a rather good lecturer, and his lectures were popular.
His mother, who had always been unhappy that her eldest son had not been good enough to study theology at university, now consoled herself that he had become a university lecturer – and at such a young age!
Carolus Linnaeus: The Science
Lapland, New Species, Classifying and Naming Plants
In the winter of 1730/31 Linnaeus continued working hard on botany in Uppsala. In particular, he had grown dissatisfied with the way plant species were classified. He began making notes about how he could improve this.
Carolus Linnaeus dressed as a native Sami in Lapland. The plant in his right hand is the Linnaea borealis, named in his honor. This was his favorite plant of all.
In 1732 he was awarded funding for an expedition to Lapland, in the far north of Sweden.
From May to October that year the 25 year-old botany lecturer traveled 1250 miles (2000 km) in Lapland, making observations of the native plants and birds. He also made geological notes.
On this journey he discovered about 100 new plants.
He wrote a book about Lapland’s plants called Flora Lapponica, describing his new discoveries. He also started using a two-part naming system – which would eventually become the Linnaean or binomial system, used worldwide to name living things.
It also came to him that he could use his new system to name animals as well as plants.
The Netherlands and a Medical Doctorate
In 1735, aged 28, Linnaeus traveled to the University of Harderwijk in the Netherlands to get a doctoral level degree in medicine. Harderwijk was famous for awarding degrees very quickly. Linnaeus had already written a thesis in Uppsala about malaria and its causes, which he submitted to Harderwijk. Within two weeks he had diagnosed a patient, defended his thesis and become a doctor of medicine!
Systema Naturae
In the Netherlands Linnaeus met Johan Frederik Gronovius, a Dutch botanist. He showed Gronovius his recent writings on the classification and naming of plants. Linnaeus had replaced some very lengthy plant names with logical, much shorter, two-part names.
Gronovius saw that Linnaeus’s work could transform botany. He became very excited.
He wanted to get the book published as quickly as possible. He contacted his friend Isaac Lawson, a Scottish doctor, and together Gronovius and Lawson paid for Linnaeus’s work to be published. And so in 1737 the first edition of Systema Naturae (System of Nature) came to the world.
Over the years, Linnaeus continued to develop his ideas and add new species so that Systema Naturae grew in a period of about 30 years from 12 outsize pages in its first edition to 2400 pages in its twelfth edition. This was the first serious attempt ever made to document all of our planet’s species. It was a huge effort: Linnaeus took the apparently chaotic natural world and organized it, making it easier for everyone to grasp it and understand it.
The classification of lifeforms is called taxonomy. Linnaeus classified living things by looking for similarities. For example he would look at the teeth of different mammals to decide if they were related. In modern times, DNA is used to classify lifeforms. In the case of fossils, where no DNA is present, scientists still use similarities between fossils – and between fossils and current lifeforms – to classify them.
After publishing Systema Naturae, Linnaeus also visited England and France, where he met other scientists, collected specimens, and discussed his work.
Linnaeus was not a modest man. He was well-aware of his achievements, and in later life, he wrote of himself:
“No one has been a greater botanist or zoologist. No one has written more books, more correctly, more methodically, from personal experience. No one has more completely changed a whole science and started a new epoch.”
Carolus Linnaeus
Physician and President of the Royal Swedish Academy of Science
Linnaeus returned to Sweden in 1738, becoming a physician in the nation’s capital city, Stockholm. While in Stockholm, Linnaeus helped found the Royal Swedish Academy of Science and became its first president.
Professor of Botany
In 1741, aged 34, Linnaeus returned to Uppsala University and became a full professor of medicine, taking control of botany, natural history and the university’s botanical garden. He immediately undertook a one-month long visit to the Swedish island of Gotland with some of his new students, where together they discovered 100 new plant species.
In summertime, Linnaeus would take his botany students on walks around Uppsala to observe and record the plant and animal life they could find. This was almost a return to his early boyhood enthusiasm for plants, when he walked freely in the countryside around his village searching for plants.
When he had given his first lectures in Uppsala as a 23 year-old student, they had been popular. Now, as an older professor, his lectures were more popular than ever – and he held some of them in the botanical garden. His students were captivated by Linnaeus’s enormous enthusiasm for botany and nature.
In 1750, at the age of 43, Linnaeus was appointed as Uppsala University’s rector.
Species Plantarum – Transforming Biology
In 1753, Linnaeus published his natural science masterpiece in two volumes and 1200 pages: Species Plantarum (Plant Species). In this work, he listed all of the plant species that had been discovered at that time – almost 6000 – and classified them into about 1000 appropriate genera. This enabled him to use two-part names for all plants throughout Species Plantarum – the first time all plants had been named in this way.
Many of the plants in the two volumes had been discovered by Linnaeus’s own students. A select group of his best students (who became known as the Apostles) traveled the world spreading the word about Linnaeus’s two-part naming system, and describing new plant species, many of which they sent as specimens back to Linnaeus in Uppsala. The Apostles traveled to wild and remote places. Out of 17 Apostles, 7 died on expeditions.
In 1758, Linnaeus published the tenth edition of Systema Naturae in which he classified all of the animal kingdom into genera and gave all of the species two-part names.
Plant drawings from Systema Naturae. Linnaeus organized plants into 24 classes. This illustration shows his readers how to tell the difference between these classes.
During his career, Linnaeus named about 13,000 lifeforms and classified them into suitable categories such as mammals, birds, fish, primates, canines, etc.
Other Notable Contributions
• Linnaeus modified the Celsius temperature scale into the form that we use today. The scale had been invented by his compatriot, Anders Celsius, who had said 0 °C was the boiling point of water and 100 °C was water’s freezing point. Linnaeus realized that it would be more useful if these values were reversed and persuaded the rest of the scientific world to follow his example.
• Linnaeus was the first person to place humans in the primate family and to describe whales as mammals rather than fish and bats as mammals rather than birds. Linnaeus did not categorize humans alongside apes with any idea of an evolutionary link. He did it with the same reasoning he used to categorize all life, which was similarities he identified between species.
• Linnaeus was one of the founders of the science of ecology – describing the relationship between living organisms and their environments.
• Linnaeus’s idea of going on expeditions to study nature and gather specimens inspired Charles Darwin and Alfred Russel Wallace to go on the expeditions that led to their theories of evolution by natural selection.
• Linnaeus invented index cards. He did this in response to his ever growing lists of species which required a cataloging method that was easily expandable and easy to reorganize.
Linnaeus invented the index card system to record and store data.
The End
Carolus Linnaeus was knighted by the King of Sweden in 1761 and took the nobleman’s name of Carl von Linné.
He died at the age of 70, on 10 January, 1778, after suffering a stroke. He was survived by his wife Sara, and five children. Two of the couple’s other children died when they were very young.
Linnaeus died on his farm about 6 miles (10 km) from Uppsala. He had bought the farm 20 years before his death. The farm was called Hammarby. Linnaeus cultivated his own private gardens at Hammarby and had hoped to be buried there. In fact he was buried in Uppsala.
Today Hammarby is a museum which features exhibitions of Linnaeus’s work, his botanical collections, and a garden and a park where his love of the natural world has been preserved.

Who is Chen-Ning Yang: Biography

Born 1922.
Chen-Ning Yang thought the unthinkable and won the 1957 Nobel Prize in physics: Yang and his coworker Tsung-Dao Lee showed that parity – a property that physicists had believed was always conserved – like energy, momentum and electric charge – need not be conserved.
Yang also worked with Robert Mills to produce Yang-Mills theory, which today lies at the heart of the Standard Model in physics.
Early Life and Education
Chen-Ning Franklin Yang was born on October 1, 1922, in the city of Hefei, China.
His family moved to Beijing when he was young after his father, Wu-Chih, became a Professor of Mathematics at Tsinghua University. His mother, Meng-hua was a housewife.
Yang was schooled in Beijing until 1937, when the Japanese invasion of China forced his family to return to Hefei, and then, a year later, move to the city of Kunming. The Japanese Army did not reach Kunming, in the south-west of China, although it was bombed by the Japanese Air Force.
Yang enrolled at the National Southwestern Associated University in Kunming and was awarded a bachelor’s degree in physics in 19
In 1944 he was awarded a master’s degree in physics for his work in statistical mechanics. He was awarded his degree by Beijing’s Tsinghua University, which had relocated to Kunming.
Yang worked as a teacher until he won a United States government scholarship in 1946, which took him to the University of Chicago. There his doctoral advisor was Edward Teller, the father of the hydrogen bomb.
In 1948 Yang was awarded a Ph.D. in physics for work in the field of nuclear reactions.
Chen-Ning Yang’s Research Work
After the award of his Ph.D., Yang stayed at Chicago for a year, working with one of the giants of 20th century physics, Enrico Fermi.
In 1949 he was invited to become a theoretical physics researcher at the Institute for Advanced Study in Princeton.
The Institute had been founded in 1930 with the goal of employing the best mathematicians and physicists in the world; Albert Einstein was there from 1933 until his death in 19
Parity Conservation
Atom Smashing
During the 1950s, increasingly complex results had been coming out of particle accelerators and cosmic ray detectors, causing increasing confusion among physicists.
The accelerators were pushing ions and particles to enormous speeds, then smashing them into one another. Physicists hoped the debris from the collisions would reveal more about what matter is and how it behaves.
Cosmic rays – high energy particles reaching Earth from the sun and the stars – also produced interesting debris.
The debris from both accelerators and cosmic rays contains subatomic particles, which are generally unstable, quickly decaying into other particles.
A very high energy proton (red) ejected by the sun enters Earth’s atmosphere. We call this a cosmic ray. It collides with a particle high in Earth’s atmosphere, producing a shower of subatomic particle debris, which can help reveal some of the basic properties of matter. Image by Mpfiz, modified by this site.
The Meson Problem
Two unstable particles, the theta-meson and the tau-meson, were causing a lot of heads to be scratched.
In some senses, the theta-meson and the tau-meson looked as if they might be the same particle: their masses and the average time they took to decay into other particles seemed to be the same. The theta-meson and the tau-meson both decayed into pi-mesons, usually known as pions.
BUT, the theta decayed to produce two pions, while the tau decayed to produce three pions.
The theta and tau particles seemed to be identical, except the theta decayed to give two pions, while the tau produced three pions.
Most physicists took it as a fundamental law of the universe that when any particle decayed, its parity stayed the same.
Parity must never be broken: this meant, in a very simplified way, that the same particle could not possibly decay sometimes into two pions, and at other times into three pions. Physicists believed there was a fundamental symmetry in the universe. If parity were broken, the fundamental symmetry they believed in would also be broken.
Physicists regarded parity as a property that was conserved in the same way that energy, momentum, and electric charge are always conserved.
Yet the only difference physicists could find between the theta-meson and the tau-meson was that they decayed differently. Otherwise these mesons seemed identical.
A Daring Hypothesis: Broken Parity
What if there really were only one meson – a meson that sometimes decayed into two pions and sometimes into three pions?
Most physicists thought the idea was ludicrous; if there was one thing they could rely on Mother Nature to do, it was to preserve parity and symmetry.
Enter Yang and Lee
At the Institute for Advanced Study, Yang had started working with Tsung-Dao Lee. They had actually first met in China at the National Southwest University.
Yang was now a full professor of theoretical physics, having been promoted in 19
In summer 1956, Yang and Lee thought the unthinkable. What if parity really could be broken? At this time, Yang was 34 and Lee was 29 years old.
The meson decay they were looking at involved the weak nuclear force – the force responsible for nuclear fission and beta particle emission from atomic nuclei.
The two physicists read everything they could and carried out a large number of calculations; they wanted to see if there truly was a fundamental physical law preventing parity being broken for interactions involving the weak nuclear force. There was already good evidence that parity could not be broken for interactions involving the strong nuclear force.
They published their work late in 1956, showing they could find nothing to stop parity being broken for weak interactions and they described experiments they had devised which could prove whether parity was broken.
The Unthinkable is True = Nobel Prize
A team of physicists at the Cryogenics Physics Laboratory at the National Bureau of Standards in Washington carried out one of the experiments designed by Yang and Lee, cementing Yang and Lee’s place in the history of science.
In 1957 Yang and Lee won the Nobel Prize in Physics: they had thought the unthinkable, their calculations showed the unthinkable was possible, and they had devised experiments that had established that the unthinkable was actually true: the theta and tau mesons were actually the same particle and Mother Nature did not preserve parity. Symmetry had also been broken. At a deep level, this means that nature can tell the difference between left and right.
In the more somber words of the Nobel Prize Committee, Yang and Lee’s prize was for their:
“penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles.”
Even in the face of the theta-tau puzzle, most physicists had not seriously contemplated the possibility of parity breaking. Physics giant Richard Feynman was pleased that at one point he gave the odds of parity breaking being discovered as low as 1 in 50!
Particle physics had been held back for years by the incorrect assumption that parity could not be broken in weak interactions. Yang and Lee set particle physics free again.
The theta-tau puzzle was solved when Yang and Lee paved the way for the discovery that tau and theta mesons are identical: they represent different behaviors of the K+ meson. Sometimes a K+ meson decays to form two pions; sometimes it decays to form three pions.
Yang-Mills Theory
Prior to his Nobel Prize winning work, Yang studied the fundamental forces in particle physics and how they relate to one another.
The first unification of forces in physics had happened in the 19th century, when James Clerk Maxwell unified the electric and magnetic forces; he showed they were actually manifestations of a single force: the electromagnetic force. In doing so, Maxwell established that light is an electromagnetic wave which carries energy between electric charges.
Maxwell’s work shook physics to its core.
Ever since Maxwell set the ball rolling, physicists have dreamed of uniting all of the forces of nature into one fundamental theory: a theory of everything.
In 1954 Yang was doing some work at Brookhaven National Laboratory, where he shared an office with Robert Mills, another young physicist.
Bouncing ideas off one another, they developed a new generalization of Maxwell’s equations, now called Yang-Mills theory.
The theory produces Maxwell’s equations as a special case. In addition to explaining electromagnetic forces, Yang-Mills theory also explains interactions between nuclear particles – in doing so, it carries physics closer to a theory of everything.
“Einstein’s theory of General Relativity has a mathematical structure very similar to Yang-Mills theory.”
Chen-Ning Yang
50 Years of Yang-Mills Theory
Yang-Mills theory now lies at the heart of the Standard Model of particle physics. The Standard Model tries to tie together the electromagnetic force, the weak nuclear force, the strong nuclear force, and all of the subatomic particles into a single consistent system – a theory of everything.
Yang–Mills theory is one of the seven Millennium Prize Problems in mathematics. Anyone solving a Millennium Prize Problem will be awarded $1 million.
The Yang-Mills millennium problem asks scientists to rigorously establish quantum Yang-Mills theory and to solve a further Yang-Mills issue known as the mass gap.
Today, more than fifty years after it was born, Yang–Mills theory is a very active research field in physics.
Other Information
Yang was married to Chi-Li Tu from 1950 until she died in 20He has three children from this marriage. In 2004, he married Weng Fan.
Although he has been an American citizen since 1964, he now lives in China, where he is an honorary director of Tsinghua University, Beijing – his father’s old university, and the university where he studied for his master’s degree.

Who is David Hilbert: Biography

David Hilbert was one of the mathematical greats of the 19th and 20th centuries. Today, mathematics and physics are still powerfully influenced by his work and his vision.
Early Life and Education
David Hilbert was born on January 23, 1862, in Königsberg, Prussia, on the Baltic Sea. Prussia later merged into Germany. Since the end of World War 2, Königsberg has been called Kaliningrad and is part of Russia.
David Hilbert’s parents were Otto Hilbert, who was a judge, and Maria Therese Erdtmann. His father came from a legal family, while his mother’s family were merchants. Both families were protestant, and his father held the faith rather strongly. His mother’s interests shaped the young boy’s interests – she was an enthusiastic amateur mathematician and astronomer.
At the age of 10, Hilbert began as a student at the Friedrichskollegium Gymnasium – a high school for academically talented children, where he studied for seven years. In his final high school year, he transferred to the more specialist math-science Wilhelm Gymnasium. He graduated from the Wilhelm Gymnasium at the highest academic level – good enough to study for a degree at any European university.
His mathematics teacher, whose name was Hermann von Morstein, wrote a note of recommendation for him, saying:
“Hilbert has a comprehensive knowledge of mathematics, with the ability to solve problems using his own methods.”
Of that time, Hilbert himself recalled:
“I didn’t work especially hard at mathematics at school, because I knew that’s what I’d be doing later.”
Hilbert decided to stay close to home: in 1880, aged 18, he enrolled to study mathematics at the University of Königsberg.
Five years later, he had not only obtained a degree in mathematics, but a Ph.D. too.
After completing his Ph.D. Hilbert spent winter at the University of Leipzig and then Paris.
In 1886 he became a mathematics lecturer at the University of Königsberg.
While studying for his degrees, Hilbert made friends with two other exceptionally talented mathematicians, Hermann Minkowski, a fellow student, and Adolf Hurwitz, an associate professor. The three pushed one another to ever greater mathematical heights – they would continue to exchange ideas for the rest of their careers.
David Hilbert’s Career
Starting in 1886, David Hilbert worked for nine years at the University of Königsberg, first as a lecturer, then as a professor.
In 1895, aged 33, he moved to became a professor at the world’s then top mathematics university, the University of Göttingen, Germany, where giants such as Carl Friedrich Gauss, Bernhard Riemann and Peter Dirichlet had been professors of mathematics. Hilbert would spend the rest of his career at Göttingen.
In 1902, at the age of 40, he became co-editor of the world’s leading mathematical journal, Mathematische Annalen.
He retired from his research and teaching work at the University of Göttingen in 1930, aged
He continued working as co-editor of Mathematische Annalen until 19
Mathematical Achievements
Hilbert was a pure mathematician. His knowledge of mathematics was unusually broad as well as deep, and he contributed to several areas of mathematics and also physics.
The mathematics he did is often at a level that can stretch the best of us, so here are brief summaries of some of his most famous achievements.
Hilbert’s Basis Theorem Proof
In 1888, Hilbert proved the finite basis theorem for any number of variables. In 1868, Paul Gordan had been able to prove the theorem, but for only two variables: three or more variables were simply too time consuming to prove. Hilbert used an entirely new abstract strategy for his proof, establishing that the theorem was true for an arbitrary number of variables. This was a major advance in algebraic number theory.
Hilbert’s Axioms of Geometry
In 1899, Hilbert published Foundations of Geometry.
Geometry, like arithmetic, requires for its logical development only a small number of simple, fundamental principles. These fundamental principles are called the axioms of geometry.
David Hilbert
Hilbert’s new axioms of geometry replaced those of Euclid from over 2000 years earlier, unifying two dimensional and three dimensional geometry into one system.
Hilbert’s 23 Problems
In 1900, Hilbert took a sweeping overview of mathematics. He then defined his famous 23 problems. In doing so, he had a greater effect in shaping mathematics in the 20th century than any other person. Hilbert outlined 23 problems or questions he thought, if answered correctly, would carry mathematics to a new level. The list, he said, was not meant to exclude other problems. It was merely a sample of problems.
Sample or not, since Hilbert first posed the 23 Problems, a huge amount of work has been done seeking the answers.
Mathematicians solved some of the problems within a few years, and others later, but some remain unsolved. Over one hundred years since Hilbert first listed them, the solution of these problems would still shine a bright new light on mathematics.
The remaining great unsolved problems Hilbert identified are:
• The Riemann Hypothesis
• The Kronecker-Weber theorem extension
• The problem of the topology of algebraic curves and surfaces
Is mathematics doomed to suffer the same fate as other sciences that have split into separate branches?… Mathematics is, in my opinion, an indivisible whole… May the new century bring with it ingenious champions and many zealous and enthusiastic disciples.
David Hilbert
The total subject of mathematics is clearly too broad for any of us. I do not think that any mathematician since Gauss has covered it uniformly and fully; even Hilbert did not and all of us are of considerably lesser width quite apart from the question of depth than Hilbert.
John von Neumann, 1903 – 1957, Mathematical Polymath
Mathematical Physics
Although he was primarily a pure mathematician, Hilbert had broad tastes in mathematics.
There is little if any separation between applied mathematics and mathematical physics. Hilbert sometimes dabbled in this area, often as a result of discussions with Hermann Minkowski, his old friend from his student days.
After graduating, Minkowski had gone on to teach Albert Einstein in Zurich. In 1907 he had taken Einstein’s Special Theory of Relativity, published in 1905, and shown that it could be advantageous to consider it differently – in four-dimensional spacetime – now called Minkowski Spacetime.
Gradually a fascination with mathematical physics grew in Hilbert, and he spent increasing amounts of time thinking about the subject.
By 1912 it had become his primary research field. He believed that most physicists approached problems with insufficient mathematical rigor. He believed that physics would benefit from the more rigorous approach that pure mathematicians brought to problems.
Physics is actually too hard for physicists.
David Hilbert
The Gravitational Field Equations of General Relativity
In summer 1915, Albert Einstein came to Göttingen at Hilbert’s invitation to lecture for a week. For years he had been struggling to express his (as yet) unpublished General Theory of Relativity mathematically.
The meeting between the two great minds was obviously fruitful, because by November, they had independently derived and published field equations of gravitation, putting Einstein’s General Theory of Relativity on firm mathematical ground. Hilbert and Einstein used different methods to find the equations – each method had its own strengths and weaknesses.
Hilbert never claimed any credit for the discovery of these equations, giving the credit to Einstein. Nevertheless, for some applications, Hilbert’s treatment of the field equations can be rather helpful.
Hilbert Space
Hilbert extended vector algebra and calculus so they could be used in any number of dimensions. This was a huge advance in the development of both mathematics and physics. Today, Hilbert Space is essential in quantum mechanics, Fourier analysis, and in the application of partial differential equations, which are numerous in physics and physical chemistry.
Hilbert’s Program: Logic and the Foundation of Mathematics
In 1920 Hilbert founded mathematical formalism. He did this after realizing that there were inconsistencies at the heart of arithmetic. He hoped to repeat with arithmetic and number theory the success he had enjoyed in 1899 with the axioms of geometry.
By choosing the correct axioms, he hoped to prove that the rest of classical mathematics would follow naturally.
In 1931, Kurt Gödel was able to establish that Hilbert’s Program could never be fully achieved. Gödel’s Incompleteness Theorems proved that there are mathematical statements which, although true, can never be mathematically proved.
Hilbert’s Retirement
David Hilbert retired from his professorship in 19His retirement years were spent living in Nazi Germany. Jewish mathematicians, many of whom had been his friends, were banished from Göttingen: they all left for other countries.
It was a sad, rather lonely end for a brilliant, exceptionally influential mathematician, who had been a friend to everyone, and who was known for his zest for life.
When he had first arrived as a new professor at Göttingen he had upset the older professors by going to the local billiard hall, where he played against his juniors. He was worshiped by his many students, whom he made a point of going on walks with, so they could talk about mathematical problems informally.
David Hilbert died at the age of 81 on February 14, 1943, in Göttingen. Only about 10 people attended his funeral, a pitiful number for a great and much loved mathematician. For one reason or another, the Nazis had more or less cleared Göttingen’s mathematics faculty of people Hilbert had known.
David Hilbert is buried in Göttingen.
After Hilbert’s death, Hermann Weyl, a former student of Hilbert, who left Germany for America because his wife was Jewish, wrote:
No mathematician of equal stature has risen from our generation… Hilbert was singularly free from national and racial prejudices; in all public questions, be they political, social or spiritual, he stood forever on the side of freedom.
Hermann Weyl, 1885 to 1955
David Hilbert was survived by his wife Käthe Jerosch and son Franz. Franz was intellectually challenged and suffered from one or more mental disorders. He spent some time in a mental hospital. David Hilbert found it hard to come to terms with his son’s condition. Käthe Jerosch died in 1945, and Franz died in 19
Although this ending seems rather sad, Hilbert was a man who was forever optimistic about the future of human culture and science. When he was a young man, the beliefs of the physiologist Emil du Bois-Reymond had been in vogue.
Du Bois-Reymond and his followers believed there were some things that humans would never know. They thought there were limits on our ability to gather scientific knowledge. Famously, they said: ignoramus et ignorabimus, meaning “we do not know and will not know.”
In response, in 1930, Hilbert gave a radio broadcast in which he responded to this gloomy outlook:
We must not believe those who today, with philosophical bearing and superior tone, prophesy the decline of culture and accept the ignorabimus principle. For us there is no ignorabimus, and in my opinion none at all in natural science. Rather than this foolish ignorabimus our slogan shall be: Wir müssen wissen, wir werden wissen! (‘We must know, we will know!’)
David Hilbert
These six words – Wir müssen wissen, wir werden wissen – are the most famous words David Hilbert ever said. They are the epitaph on his gravestone in Göttingen and a rallying cry for all scientists.

Who is Dmitri Mendeleev: Biography

Lived 1834 – 19
Dmitri Mendeleev was passionate about chemistry. His deepest wish was to find a better way of organizing the subject.
Mendeleev’s wish led to his discovery of the periodic law and his creation of the periodic table – one of the most iconic symbols ever seen in science: almost everyone recognizes it instantly: science has few other creations as well-known as the periodic table.
Using his periodic table, Mendeleev predicted the existence and properties of new chemical elements. When these elements were discovered, his place in the history of science was assured.
Early Life and Education
Dmitri Ivanovich Mendeleev was born February 8, 1834 in Verkhnie Aremzyani, in the Russian province of Siberia. His family was unusually large: he may have had as many as 16 brothers and sisters, although the exact number is uncertain.
His father was a teacher who had graduated at Saint Petersburg’s Main Pedalogical Institute – a teacher training institution.
When his father went blind, his mother re-opened a glass factory which had originally been started by his father and then closed. His father died when Mendeleev was just 13 and the glass factory burned down when he was
Aged 16, he moved to Saint Petersburg, which was then Russia’s capital city. He won a place at his father’s old college, in part because the head of the college had known his father. There, Mendeleev trained to be a teacher.
By the time he was 20, Mendeleev was showing his promise and publishing original research papers. Suffering from tuberculosis, he often had to work from bed. He graduated as the top student in his year, despite the fact that his uncontrollable temper had made him unpopular with some of his teachers and fellow students.
In 1855, aged 21, he got a job teaching science in Simferopol, Crimea, but soon returned to St. Petersburg. There he studied for a master’s degree in chemistry at the University of St. Petersburg. He was awarded his degree in 18
Chemistry
Mendeleev had trained as both a teacher and an academic chemist. He spent time doing both before he won an award to go to Western Europe to pursue chemical research.
He spent most of the years 1859 and 1860 in Heidelberg, Germany, where he had the good fortune to work for a short time with Robert Bunsen at Heidelberg University. In 1860 Bunsen and his colleague Gustav Kirchhoff discovered the element cesium using chemical spectroscopy – a new method they had developed, which Bunsen introduced Mendeleev to.
In 1860, Mendeleev attended the first ever international chemistry conference, which took place in Karlsruhe, Germany. Much of the conference’s time was spent discussing the need to standardize chemistry.
This conference played a key role in Mendeleev’s eventual development of the periodic table. Mendeleev’s periodic table was based on atomic weights and he watched as the conference produced an agreed, standardized method for determining these weights.
At the conference, he also learned about Avogardo’s Law which states that:
All gases, at the same volume, temperature and pressure, contain the same number of molecules.
By the time he returned to Saint Petersburg in 1861 to teach at the Technical Institute, Mendeleev had become even more passionate about the science of chemistry. He was also worried that chemistry in Russia was trailing behind the science he had experienced in Germany.
He believed that improved Russian language chemistry textbooks were a necessity, and he was determined to do something about it. Working like a demon, in just 61 days the 27 year old chemist poured out his knowledge in a 500 page textbook: Organic Chemistry. This book won the Domidov Prize and put Mendeleev at the forefront of Russian chemical education.
Mendeleev was a charismatic teacher and lecturer, and held a number of academic positions until, in 1867, aged just 33, he was awarded the Chair of General Chemistry at the University of Saint Petersburg.
In this prestigious position, he decided to make another push to improve chemistry in Russia, publishing The Principles of Chemistry in 18Not only did this textbook prove popular in Russia, it was popular elsewhere too, appearing in English, French and German translations.
“Knowing how contented, free, and joyful is life in the world of science, one fervently wishes that many would enter its portals.”
Dmitri Mendeleev, 1834 to 1907
Chemist
The Periodic Table
At this time, chemistry was a patchwork of observations and discoveries.
Mendeleev was certain that better, more fundamental principles could be found; this was his mindset when, in 1869, he began writing a second volume of his book The Principles of Chemistry.
At the heart of chemistry were its elements. What, wondered Mendeleev, could they reveal to him if he could find some way of organizing them logically?
He wrote the names of the 65 known elements on cards – much like playing cards – one element on each card. He then wrote the fundamental properties of every element on its own card, including atomic weight. He saw that atomic weight was important in some way – the behavior of the elements seemed to repeat as their atomic weights increased – but he could not see the pattern.
Convinced that he was close to discovering something significant, Mendeleev moved the cards about for hour after hour until finally he fell asleep at his desk.
When he awoke, he found that his subconscious mind had done his work for him! He now knew the pattern the elements followed. He later wrote:
“In a dream I saw a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper.”
Dmitri Mendeleev, 1834 to 1907
Chemist
It took him only two weeks to publish The Relation between the Properties and Atomic Weights of the Elements. The Periodic Table had been unleashed on the scientific world.
Why was Mendeleev’s Periodic Table Successful?
As with many discoveries in science, there is a time when a concept becomes ripe for discovery, and this was the case with the periodic table in 18
Lothar Meyer, for example, had proposed a rough periodic table in 1864 and by 1868 had devised one that was very similar to Mendeleev’s, but he did not publish it until 18
John Newlands published a periodic table in 18Newlands wrote his own law of periodic behavior:
“Any given element will exhibit analogous [similar] behavior to the eighth element following it in the table”
Newlands also predicted the existence of a new element (germanium) based on a gap in his table. Unfortunately for Newlands, his work was largely ignored.
The reason Mendeleev became the leader of the pack was probably because he not only showed how the elements could be organized, but he used his periodic table to:
• Propose that some of the elements, whose behavior did not agree with his predictions, must have had their atomic weights measured incorrectly.
• Predict the existence of eight new elements. Mendeleev even predicted the properties these elements would have.
It turned out that chemists had measured some atomic weights incorrectly. Mendeleev was right! Now scientists everywhere sat up and paid attention to his periodic table.
And, as new elements that he had predicted were discovered, Mendeleev’s fame and scientific reputation were enhanced further. In 1905, the British Royal Society gave him its highest honor, the Copley Medal, and in the same year he was elected to the Royal Swedish Academy of Sciences.
Element 101 is named Mendelevium in his honor.
“Dmitri Mendeleev was a chemist of genius, first-class physicist, a fruitful researcher in the fields of hydrodynamics, meteorology, geology, certain branches of chemical technology and other disciplines adjacent to chemistry and physics, a thorough expert of chemical industry and industry in general, and an original thinker in the field of economy.”
Lev Aleksandrovich Chugaev, 1873 to 1922
Chemist
The End
Dmitri Mendeleev died in Saint Petersburg, February 2, 1907, six days before his 73rd birthday. He was killed by influenza.

Who is Eratosthenes: Biography

Lived c. 276 BC – c. 194 BC.
Eratosthenes was an Ancient Greek scientist born in the town of Cyrene in about 276 BC. Cyrene is now the town of Shahhat in Libya. He was educated in philosophy and mathematics in Athens. We do not really know what he looked like. This image above is from a painting by Bernardo Strozzi in the year 1635, 19 centuries after the era of Eratosthenes. It shows Eratosthenes teaching geography, the academic discipline he invented.
Quick Guide – Eratosthenes’ Greatest Achievements
• Eratosthenes produced a reliable, logical method to discover prime numbers: The Sieve of Eratosthenes. In an updated form, this is still important in modern number theory.
• Assuming Earth was a sphere, in about 240 BC Eratosthenes calculated its size with good accuracy. This was a moment of triumph for the human intellect: first to realize our planet was a sphere, then to use the powers of observation, deduction and mathematics to calculate its size.
• Eratosthenes knew that Earth rotated once a day around an axis that formed an imaginary line from the North Pole to the South Pole through the center of the earth. He calculated the tilt of Earth’s axis with good accuracy.
• He produced the first map of the world which used meridian lines and parallel lines. These were similar to our modern lines of latitude and longitude. He marked the equator and its size, considered the size of the polar zones and how far these zones were from the tropics. (Evidently, the Ancient Greeks knew a lot about our planet!)
• He invented geography. Today we still use the word he invented for this new discipline. (‘Geo’ was Greek for ‘Earth’ and ‘graphy’ meant ‘field of study.’)
• He produced a timeline recording all of the achievements of science since the time the Greeks had laid siege to Troy.
• He was the first person to explain why the River Nile flooded every year – i.e. that heavy, seasonal rains fall near the source of the river, resulting in an annual flood in Egypt.
• He rejected the commonly held view that people could be divided into ‘Greeks’ and ‘Barbarians.’ He held that people should be judged as individuals on their good and bad qualities.
A Rounded Character
Not restricting himself to science, Eratosthenes excelled at nearly all things intellectual. He wrote books on philosophy, geography, mathematics, astronomy, history, comedy, and also wrote poetry.
This all-round knowledge made him a shoe-in for one very special job. That job was the most prestigious role an academic could enjoy in Ancient Greece – Director of the Library of Alexandria, the greatest intellectual institution of the ancient world.
The Library of Alexandria is said to have contained over half a million books in scroll form. It was the place the greatest scientists, mathematicians, philosophers, poets, and dramatists gathered to talk about their intellectual quests. The Library had lecture halls and meeting rooms. Today, we would call it a great university.
Eratosthenes had his fans and his critics. Both seemed to have used the same nicknames for him. Eratosthenes had two nicknames we know about. One of these was ‘Beta’ the second letter of the Greek alphabet. This was because Eratosthenes, although he knew about everything, was not the absolute best at anything. ‘Beta’ could be used as an insult or a compliment.
The other nickname he was given was ‘the pentathlete.’ The meaning is similar to Beta, in that a pentathlete has to be very good at five different sports, but will probably not be a champion in any of the individual sports.
Eratosthenes called himself ‘philologos’ – ‘lover of learning.’
The greatest minds of Greece would send their work to Eratosthenes as papyrus scrolls. Ever curious, Eratosthenes would take time to read many of these before his assistants cataloged them.
Cataloging of scrolls at the Library of Alexandria, drawn in the 1800s based on the scholarship of the time.
His friend, the great Archimedes, entrusted him with an enormously important treatise called The Method. In addition to containing the most advanced mathematics the world had ever seen, The Method gives us some clues about Eratosthenes’ interests. Archimedes writes (loosely translated):
“Since I know you care about your work, are an excellent teacher of philosophy, and greatly interested in mathematical investigations, I thought I’d let you know about my special method. The method will enable you to use mechanics to see the answers to mathematical questions…”
And so we learn that Eratosthenes is a fantastic teacher, as well as an intellectual. (Not all intellectuals are good teachers!)
Of course, Eratosthenes did not only read about great work carried out by other people. He did some great work himself.
We know him best for two important achievements: producing an accurate estimate of how big Earth is; and devising a method to find prime numbers.
Unfortunately, other than a few scraps, little remains of Eratosthenes’ original work. We usually have to rely on comments from people who were around at the time and in the following few centuries to get an idea of what Eratosthenes wrote.
How Big is Planet Earth?
As Director of the Library of Alexandria, Eratosthenes had the closest thing in the ancient world to a modern internet search engine. Everything that had been learned about the world by the Greeks – and that was a lot – was within his reach.
Eratosthenes had learned that at midday, on the longest day of the year, walls in the city of Syene cast no shadows, because the sun was directly overhead. He could see with his own eyes in Alexandria that there were small shadows at midday on the longest day.
Syene was more-or-less due south of Alexandria, therefore the angle of the shadow must mean something. What did it mean?
Eratosthenes reasoned that if:
you make the assumption that planet Earth is a sphere
the sun’s rays are parallel to one another when they reach Earth
you measure the angle of the shadow in Alexandria when there is no shadow in Syene
you know the distance between Alexandria and Syene
then, you could calculate how big Earth is.
Some Key Parts of Eratosthenes’ Reasoning
The Calculation
On the diagram above, the angle z is the angle of shadow Eratosthenes found in Alexandria. He found it was one-fiftieth of a whole circle.
Using a little simple Euclidean geometry, he knew that by drawing a line downward from each wall to the center of the earth, they would form the same angle z.
This meant that the distance from Syene to Alexandria was one-fiftieth of the distance all the way around planet Earth.
His maps told Eratosthenes that the distance from Alexandria to Syene was 5000 stades. Eratosthenes multiplied 50 x 5000 to get an answer of 250,000 stades for Earth’s circumference. He then added a correction of 2000 stades (lacking his original work, we don’t know why he did this) and concluded that:
Earth’s circumference is equal to 252,000 stades
All we need to do now is convert stades to modern units. (Some things are easier said than done!)
How Good Was Eratosthenes’ Estimate of Earth’s Size?
We can’t say exactly how good his estimate was, because the ‘stade’ unit of length meant different things to different people.
Most likely, Eratosthenes would have said which type of stade he was using when he wrote his book, ‘On the Measurement of the Earth,’ but the book is lost in the mists of time.
Whichever stade was used, Eratosthenes overestimated the size of Earth. Depending on which stade he used, we can say that his estimate was, at best, within 1% and, at worst, within about 30% of the value we use now. (Our current value for Earth’s polar circumference is 40,075.16 km or 24,901.55 miles.) Whichever way you look at it, this was an enormous advance in an era when most people in the world had no idea that our planet is approximately spherical.
The Sieve of Eratosthenes
Using his ‘seive’ Eratosthenes solved the problem of how to find prime numbers logically and systematically.
Prime numbers are those numbers with no factors except for themselves and Mathematicians look on them in the same way as chemists look on the chemical elements. Prime numbers are the building blocks of all other numbers.
The first eight prime numbers are 2, 3, 5, 7, 11, 13, 17 and The prime numbers go on forever. There are an infinite number of them. This had already been proved by the Greeks, and the proof was written in Euclid’s Elements.
To use the Sieve of Eratosthenes, first decide the highest number you wish to check. Then, starting at 2, write down all of the numbers up to the highest number. Say you wanted to check all the numbers up to 110, you would write:
You would then remove 1, since it’s not prime, and leaving 2, which is prime, you would remove every second number from 2 onwards, to get:
And now, leaving 3 alone, you remove every multiple of 3, to get:
The next number to leave is Remove every multiple of 5 to get:
The next number to leave is Remove every multiple of 7 to get:
Repeat this process until all the primes have been found. In the case of primes up to 110, they are all shown in the final table above. All of the numbers that are not prime have been sieved out using Eratosthenes’ method.
The procedure can be used to find primes to as high a limit as you like.
The End of Eratosthenes
Legend has it that Eratosthenes went blind and died by starving himself when he was 80 to 82 years old.

Who is Ernest Rutherford: Biography

Lived 1871 – 19
Ernest Rutherford is the father of nuclear chemistry and physics. He discovered and named the atomic nucleus, the proton, the alpha particle, and the beta particle. He discovered the concept of nuclear half-lives and achieved the first deliberate transformation of one element into another, fulfilling one of the ancient passions of the alchemists.
Beginnings
Ernest Rutherford was born on August 30, 1871, in the village of Brightwater on New Zealand’s South Island. His father, James Rutherford, was a farmer from Scotland and his mother, Martha Thompson, was a schoolteacher from England.
Ernest was the fourth of the 12 children his parents brought up in New Zealand, and he was blessed with both high intelligence and a talent for sports, particularly rugby football. He read his first science book at the age of 10, and was enthralled by what he learned, carefully performing the experiments the book suggested.
He attended high school at Nelson College, in the small town of Nelson, where his boarding fees were funded by a scholarship.
At the age of 18 he left for the city of Christchurch, where he had won a scholarship to Canterbury College, now the University of Canterbury.
In 1893 he graduated with first class honors in both mathematics and physical science.
In 1895 he obtained a bachelors degree in chemistry and geology from Canterbury College and spent a short time working as a schoolteacher. He then won a scholarship that enabled him to study overseas. He decided to go to the University of Cambridge in the United Kingdom to work in J. J. Thomson’s laboratory.
Cambridge, Montreal, Manchester and back to Cambridge
Rutherford arrived in Cambridge in 1895 and the 24-year-old newcomer was made to feel very welcome by J. J. Thomson and his wife Rose.
Rutherford had already invented a radio receiver in New Zealand and improved on it at Cambridge, where he built a world-record-breaking receiver capable of detecting radio waves at half-a-mile. However, the battle to develop radio was one he would quickly lose to Guglielmo Marconi. Rutherford did not mind in the least. His radio work was not as intellectually stimulating as other work he did at Cambridge on radioactivity and the effects of X-rays on gases.
Rutherford’s research work was remarkably advanced for such a young man, impressing Thomson enormously. In 1898, when a Chair in physics came up at Montreal’s McGill University, Thomson recommended Rutherford should be appointed to it.
“I have never had a student with more enthusiasm or ability for original research than Mr. Rutherford.”
J. J. Thomson
Nobel Prize in Physics 1906
And so in 1898 Rutherford sailed to Canada, taking up a professorship, aged just At McGill he carried out the work which led to his 1908 Nobel Prize in Chemistry.
In 1907, after nine years at McGill, Rutherford sailed back to the UK, where he had been appointed to the University of Manchester’s Chair of Physics.
Rutherford’s final move came in 1919 with J. J. Thomson’s retirement as the Cavendish Professor of Experimental Physics at the University of Cambridge. Rutherford, his old student, now aged 48, was appointed as his replacement.
Rutherford’s Most Significant Contributions to Science
Discovery of alpha and beta radiation
Starting in 1898 Rutherford studied the radiation emitted by uranium. He discovered two different types of radiation, which he named alpha and beta.
By allowing radiation from uranium to pass through an increasing number of layers of metal foil, he discovered that:
• beta particles have greater penetrating power than alpha rays
By the direction of their movement in a magnetic field, he deduced that:
• alpha particles are positively charged
By measuring the ratio of mass to charge, he formed the hypothesis that:
• alpha particles are helium ions carrying a 2+ charge
With his co-worker, Frederick Soddy, Rutherford came to the conclusion that:
• alpha particles are atomic in nature
• alpha particles are produced by the disintegration of larger atoms – and so atoms are not, as everyone had believed, indestructible
• when large atoms emit alpha particles they become slightly smaller atoms – so a radioactive element changes into other elements when it decays
Soddy, who would himself later win a Nobel Prize, was exhausted by the effort of keeping up with Rutherford:
“I abandoned all to follow him (Rutherford). For more than two years, scientific life became hectic to a degree rare in the lifetime of an individual, rare perhaps in the lifetime of an institution.”
Frederick Soddy, 1877 to 1956
Nobel Prize in Chemistry 1921
Rutherford coined the terms alpha, beta, and gamma for the three most common types of nuclear radiation. We still use these terms today. (Gamma radiation was discovered by Paul Villard in Paris, France in 1900.)
Rutherford began his investigation of alpha and beta radiation in the same year that Pierre and Marie Curie discovered the new radioactive elements polonium and radium.
“I have to keep going, as there are always people on my track. I have to publish my present work as rapidly as possible in order to keep in the race. The best sprinters in this road of investigation are Becquerel and the Curies.”
Ernest Rutherford
In 1907 Rutherford discovered that radioactive elements have half-lives – he coined the term half-life period to identify the phenomenon.
Rutherford was awarded the 1908 Nobel Prize in Chemistry “for his investigations into the disintegration of the elements, and the chemistry of radioactive substances.”
The age of planet Earth and radiometric dating
Rutherford realized that Earth’s helium supply is largely produced by the decay of radioactive elements. He devised a method of dating rocks relating their age to the amount of helium present in them.
Based on the fact that our planet is still volcanically active, Lord Kelvin had indicated Earth’s age could be no greater than 400 million years old. He said Earth could be older than this only if some new source of energy could be found that was heating it internally.
Rutherford identified the new source – the energy released by radioactive decay of elements.
He also began the science of radiometric dating – using the products of radioactive decay to find out how old things are.
“Lord Kelvin had limited the age of the Earth, provided no new source (of energy) was discovered. That prophetic utterance refers to what we are now considering tonight, radium!”
Ernest Rutherford
Discovery of the atomic nucleus
After his move to the University of Manchester, Rutherford and two of his researchers – Hans Geiger and Ernest Marsden – carried out in 1909 one of the landmark experiments in science – the gold foil experiment.
Rutherford began the experiment because he was puzzled that fewer alpha particles than expected from a sample of radium were reaching a new detector in his laboratory. The only medium the particles had to travel through was a small amount of air. The huge amount of energy carried by alpha particles should allow them to travel through a small amount of air undisturbed, with no deflection.
He gave Geiger and Marsden the task of investigating to what extent alpha particles would be deflected from their usual straight-line path by passing through a very thin sheet of gold foil.
Geiger and Marsden used a sample of radium to provide a stream of alpha particles, which passed through the gold foil. Where the alpha particles ended up was recorded electrically.
The results were remarkable. If gold were a smooth substance on the atomic scale, as it had been thought to be, a slight deflection of alpha particles would have been expected. In fact, most alpha particles shot straight through the gold without deflection, but a few were deflected enormously, some even ‘bouncing’ straight back from the gold. Rutherford was utterly amazed by this. Famously, he likened it to firing a battleship’s guns at tissue paper and discovering some of the shells were bouncing back from the tissue paper.
Rutherford explained the effect by proposing a new model for the atom, replacing the plum pudding model of his old mentor J. J. Thomson.
His new model required atoms to have a small, very dense core. And with this step, inspired by his experimental data, Rutherford had discovered the atomic nucleus.
J. J. Thomson had modeled the atom as a sphere in which positive charge and mass were evenly spread. Electrons orbited within the positive sphere. This was called the plum pudding model.
The results of the gold foil experiment allowed Rutherford to build a more accurate model of the atom, in which nearly all of the mass was concentrated in a tiny, dense nucleus. Most of the atom’s volume was empty space. The scale was such that the nucleus was like a fly floating in a football stadium – remembering of course that the fly was much heavier than the stadium! Electrons orbited at some distance from the nucleus. This was called the Rutherford model. It resembles planets orbiting a star.
Although Rutherford had received a Nobel Prize for his earlier work, his discovery of the atomic nucleus was probably his greatest achievement.
A 26-year-old Niels Bohr, who was spending time as a research student in Rutherford’s laboratory in 1912, was intrigued by Rutherford’s model of the atom. He could see that in terms of classical physics, the separation of charge into positive nucleus and orbiting electrons was unstable. He explored the implications of such an atom, leading directly to the first quantum model of the atom – the Rutherford-Bohr atom.
“Rutherford is a man you can rely on; he comes regularly and enquires how things are going and talks about the smallest details – Rutherford is such an outstanding man and really interested in the work of all the people around him.”
Niels Bohr, 1885 to 1962
Nobel Prize in Physics 1922
Discovery of nuclear reactions
Rutherford achieved the first deliberate transformation of one element into another. In 1919 he converted nitrogen atoms into oxygen atoms by bombarding nitrogen with alpha particles. This nuclear reaction was initially written:
14N + α → 17O + 1H
Discovery of the proton
Finding hydrogen produced in the nuclear reaction above, Rutherford began to suspect that the hydrogen nucleus may actually be a fundamental particle, a building block of all atomic nuclei.
He formalized this in 1920 by giving this particle a name: the proton. The first nuclear reaction could now be written:
14N + α → 17O + proton
Predicting the existence of the neutron
Rutherford carried out calculations of the stability of atomic nuclei. He found that unless some neutral particle were added to the nucleus, the repulsion of the positively charged protons would cause nuclei to fly apart. In 1920 he named this hypothetical particle the neutron.
James Chadwick, Rutherford’s Assistant Director of Research, discovered the neutron in 1932, proving its existence by experiment.
Some Personal Details and the End
Rutherford did not exactly conform to the scientific stereotype. He was a direct, no-nonsense man, who spoke his mind. He was not overly concerned with his appearance; some people mistook the great scientist for a farmer!
He was well-known for his limitless reserves of energy and enthusiasm, which left a number of his workers exhausted.
“Rutherford’s enthusiasm and abounding vigor naturally affected us all. To work in the laboratory in the evening was the rule rather than the exception, particularly for us Germans, whose stay in Montreal was limited… He had a great, hearty laugh which echoed through the whole laboratory.”
Otto Hahn, 1879 to 1958
Nobel Prize in Chemistry 1944
In summer 1900, two years after moving to Montreal, Rutherford sailed for New Zealand to marry Mary Georgina Newton, whom he had become engaged to while living in Christchurch. They had one child, Eileen Mary, born in 19When she was 20, Eileen married the renowned physicist Ralph H. Fowler. Eileen died in 1930, nine days after giving birth to her fourth child. Rutherford and his wife outlived their daughter, taking solace in their grandchildren, all of whom became academics.
Rutherford would visit his research workers daily, approving or disapproving, critical or praising the work they had been doing, listening to their problems, making suggestions. He could be blunt when he thought people were doing things wrongly, but his workers revered him because they knew that above all else, all of his energy was being applied to push the frontiers of human knowledge, and he always gave his workers full credit for their research.
Rutherford was an inspiring man and, as had been the case with J. J. Thomson, an unusually large number of his research workers went on to win Nobel Prizes, including James Chadwick, Cecil Powell, Niels Bohr, Otto Hahn, Frederick Soddy, John Cockcroft, Ernest Walton and Edward Appleton.
His booming voice was the loudest many of his colleagues had ever heard. Geoffrey Fellows, a fellow lecturer at Cambridge, wrote:
We were a polite society and I expected to lead a quiet life teaching mechanics and listening to my senior colleagues gently but obliquely poking fun at one another. This dream of somnolent peace vanished very quickly when Rutherford came to Cambridge. Rutherford was the only person I have met who immediately impressed me as a great man. He was a big man and made a big noise and he seemed to enjoy every minute of his life. I remember that when transatlantic broadcasting first came in, Rutherford told us at a dinner in Hall how he had spoken into a microphone to America and had been heard all over the continent. One of the bolder of our Fellows said: “Surely you did not need to use apparatus for that.”
Geoffrey Fellows, 1871 to 1937
During his lifetime, Rutherford received many honors. In addition to his Nobel Prize, he was knighted in 1914, becoming Sir Ernest Rutherford, and then made a British lord, receiving the title Baron Rutherford of Nelson in 19
Ernest Rutherford died of intestinal paralysis at the age of 66, on October 19, 19His ashes were buried in the Nave of Westminster Abbey, joining other science greats such as Isaac Newton, Lord Kelvin, Charles Darwin, and Charles Lyell. In 1940 the ashes of his friend and former boss J. J. Thomson were laid to rest with Rutherford and the other scientists.
Element 104 is named Rutherfordium in his honor.
“Even the casual reader of Rutherford’s papers must be deeply impressed by his power in experiment… He was, in my opinion, the greatest experimental physicist since Faraday.”
James Chadwick, 1891 to 1974
Nobel Prize in Physics 1935

Sources: Famous Scientists