What is the universe: its components, laws and measures

Basic universe

"Universe", from the latin universus, is usually defined as the set of all things created (if you believe in creation), or of all things that exist.
We often use words such as "universal" or "universality" to refer to a fact or idea that all-encompassing although, often, we refer to something that does not extend beyond our planet, as when we named a "universal" artist or referring to the '' universality '' of laws, phenomena or cultural events. In these cases, although we obviously refer to the scope of our planet, we are expressing an idea of totality.
When we speak of the astronomical universe it seems more appropriate to refer to it with the Greek word "Cosmos". Although many dictionaries we find exactly the same definitions for both terms, there is a difference of nuance: "Cosmos" seems limited to matter and space, while the concept of "Universe" also includes the energy and time.
In this chapter we will try the basic aspects of the universe: what is, as shown, and which are its fundamental laws.

What is the universe?

The universe is everything, no exceptions. Matter, energy, space and time, all that exists is part of the universe.
It is very large, but not infinite. If it were, there would be infinite infinite star matter, and isn't. On the contrary: in terms of matter the universe is, above all, empty space.
The universe contains galaxies, Galaxy clusters and larger structures called Superclusters, and Intergalactic matter. We still don't know exactly the extent of the universe, despite the advanced technology available today.
The matter is not distributed evenly, but it is concentrated in specific places: galaxies, stars, planets... However, 90% of the universe is a dark mass, which can not be seen. For every million atoms of hydrogen the 10 most abundant elements are:

Symbol Chemical element Atoms
H Hydrogen 1,000,000
I have Helium 63,000
O Oxygen 690
C Carbon 420
N Nitrogen 87
If Silicon 45
Mg Magnesium 40
NE Neon 37
Faith Iron 32
S Sulphur 16

Chemical elements in the universe

Our place in the universe

Our world, the Earth, is minuscule compared with the universe. We are part of the Solar system, lost an arm in a galaxy that has 100 billion stars, but is only one among the hundreds of billions of galaxies that formed the universe.

The Big Bang theory explains how formed

He says making 13,700 million years ago the matter had infinite density and temperature. There was an explosion of violent and, since then, the universe loses density and temperature.
The Big Bang is a singularity, an exception that cannot explain the laws of physics. We know what happened from the first moment, but the timing and size zero do not yet have scientific explanation.

Observation of the Cosmos

Since its origins, the human species has been observed the sky. First, directly, then with increasingly powerful telescopes. Now, with many electronic media.
Ancient civilizations grouped the stars forming figures. Our constellations were invented in the Eastern Mediterranean about 2,500 years ago. They represent animals and myths of the time and the place. People believed that heaven bodies influenced the life of Kings and subjects. The study of the stars mingled with superstitions and rituals.
The constellations that accompany the path of the Sun, Moon and planets, in the strip called Zodiac, we are familiar: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces.
The telescope was invented at the beginning of the 17TH century. Lenses, then mirrors, also combinations of both were first used. Currently there are telescopes of very high resolution, even groups of several synchronized telescopes.
The radio telescopes detected radiation of different wavelengths. They work in groups using a technique called interferometry.
Photography, computers, communications and, in general, the technical advances of recent years have helped a lot to astronomy.
The space telescope Hubble (HST), located in orbit, and sends images and data without the distortion caused by the atmosphere.
Thanks to the spectra, produced by the decomposition of the light, we can know detailed information about the chemical composition of an object. It also applies to the knowledge of the universe.
A recent find, gravitational lenses, take advantage of the fact that objects with mass can deflect the light rays. If it locates a group of bodies with the appropriate configuration, it acts as a very powerful lens and sign, in the Center, distant objects that we could not see.

The constellations

The stars that can be seen on a clear night form certain figures that we call "constellations", and which serve to more easily locate the position of the stars.
In total, there are 88 groupings of stars that appear on the celestial sphere and which take their name from religious or mythological figures, animals or objects. This term also refers to the celestial sphere bounded areas comprising groups of stars with name.
The oldest drawings of constellations that are known indicate that the constellations had already been established the 4000 B.c. The Sumerians gave the name to the constellation Aquarius, in honor of their God An, spilling the water of immortality on Earth. The Babylonians had already divided the Zodiac into 12 equal signs around 450 BC
The current constellations of the northern hemisphere differ little from which knew the Chaldeans and the ancient Egyptians. Homer and Hesiod mentioned constellations and the Greek poet from Soli Arato, gave a description in verse of 44 constellations in his Phaenomena. Tolomeo, astronomer and mathematician Greek, in the Almagest, described 48 constellations, of which 47 are still knowing by the same name.
Many other cultures grouped stars into constellations, although not always correspond with those of the West. However, some Chinese constellations look like the Westerners, which suggests the possibility of a common origin.
At the end of the 16th century, the first European explorers of the southern seas drew maps of the southern hemisphere. The Dutch navigator Pieter Dirckz Keyser, who participated in the exploration of the East Indies in 1595 added new constellations. Other constellations of the southern hemisphere by the German astronomer Johann Bayer, who published the first extensive celestial atlas were later added.
Many others proposed new constellations, but astronomers finally agreed on a list of 88. However, the boundaries of the constellations remained a topic of discussion until 1930, when the International Astronomical Union set those limits.
To designate the approximately 1,300 bright stars, using the genitive of the constellation name, preceded by a Greek letter; This system was introduced by Johann Bayer. For example, the famous star Algol in the constellation Perseus, is called Beta Persei.
Among the best-known constellations are those found in the plane of the orbit of the Earth on the background of the fixed stars. They are the constellations of the zodiac. In addition to these, some well known include Cruz del Sur, visible from the hemisferiosur, and Ursa Major, visible from the northern hemisphere. These and other constellations allow to locate the position of important reference points as, for example, the celestial poles.
The largest constellation of the celestial sphere is Hydra, containing 68 stars visible to the naked eye. The Cruz del Sur, on the other hand, is the smallest constellation.

Measures of the universe

Not only you can measure distances, mass, volume, density and temperature; the brightness of the stars, the declination, wavelength and many other quantities is also measured.

Basic concepts

Mass: is the amount of matter in an object.
Volume: is the space occupied by an object.
Density: is calculated by dividing the mass of an object by its volume.
Temperature: the amount of heat from an object. The lowest possible temperature in the universe is 273 ° C below zero (0 ° Kelvin), that is does not have any power.

Units for measuring distances

Measuring the universe is difficult. Often they are not regular units. Distances, time and forces are enormous and, obviously, cannot be measured directly.
The Parallax technique is used to measure the distance to nearby stars. It is measuring the angle forming distant objects, Star observed and Earth in two opposite points of its orbit around the Sun.
The diameter of the Earth's orbit is 300 million KMS. Using trigonometry you can calculate the distance to the star. This technique, however, does not serve for distant objects, because the angle is too small and the margin of error, very large.

Unit Concept equivalence
astronomical (ua)
Average distance between the Earth
and the Sun. Is not used outside of the
Solar System.
149.600.000 km
Light year Distance that light travels in
a year. If a star is 10
light years, we see it as it was
10 years ago. It is the most practical.
9.46 trillion km
63.235,3 ua
Distance of a body that has
a parallax of 2 segments
arc. The more "scientific".
30,86 trillion km
3.26 light years
206.265 ua

To measure astronomical distances

The brightness of the stars

Brightness (magnitude star) is a system of measure in which each magnitude is 2,512 times brighter than the next. A magnitude 1 star is 100 times brighter than a magnitude 6. The brightest have negative magnitudes.
There are only 20 stars of magnitude equal to or less than 1. The weaker star that has been observed has a magnitude of 23.


The decline is the measurement in degrees of the angle of an object in the sky above or below the celestial equator.
Each object describes a 'circle of decline' apparent. The distance, in hours, from this to the circle of reference (which passes through the poles and the position of the Earth at the beginning of spring) is the ascent of the object.
Combining the ascension, declination, and distance determines the position relative to the Earth of an object.


The wavelength is the distance between two crests of waves light, electromagnetic, or similar. A shorter, more often. Their study provides data on space.

The laws of the universe

Nobody has imposed them, but the universe seems to be governed by laws that scientists have tried to discover throughout history.

Kepler's laws

It's three laws about the movements of the planets made by the German astronomer Johannes Kepler in the early 17TH century.
Kepler based their laws on the planetary data collected by the Danish astronomer Tycho Brahe, who was Assistant. Their proposals broke with an old belief of centuries that the planets moving in circular orbits.
First law: The planets revolve around the Sun in elliptical orbits that the Sun occupies one of the foci of the ellipse.
Second law: The areas swept by the segment linking the Sun to the planet (radio vector) are proportional to the times used to describe them. As a result of this law, how much closer is the planet of the Sun faster moves.
Third law: The squares of the sidereal periods of revolution of the planets around the Sun are proportional to the cubes of their elliptical orbits over axle shafts. This allows to infer that the more distant sun planets orbiting at a slower rate than the nearby; He says that the period of revolution depends on the distance to the Sun.
These laws played an important role in the work of the astronomer, mathematician and physicist Isaac Newton XVII century English, and are fundamental to understanding the orbital paths of the Moon and artificial satellites.

Universal gravitation

Gravitation is the property of mutual attraction that possess all the objects composed of matter. It is sometimes used as the term "gravity", although this refers only to the gravitational force that exerts the Earth
Gravitation is one of the four basic forces that control the interactions of matter. So far, they have not attempts to detect gravitational waves that suggests the theory of relativity, may be seen when the gravitational field of a massive object is disturbed.
The law of gravitation, formulated by Isaac Newton in 1684, States that the gravitational attraction between two bodies is proportional to the product their masses and inversely proportional to the square of the distance between them.

The Doppler effect

The variation of wavelength of light, electromagnetic radiation, and sound of the bodies reports on its movement.
When a vehicle approaches we hear your motor more acutely than when it moves away. Also, when we approach a star or a Galaxy, its spectrum moves toward the blue and, if away, towards the red.
At the moment, all the observed galaxies move towards the red, i.e., move away from here.
Published for educational purposes authorized by: Astronomía: Tierra, Sistema Solar y Universo

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