Constitution of the universe: Size and shape, structure, material and cosmic radiation

Advanced universe

The knowledge about our universe has many levels. the "Basic universe", was elementary aspects, this let's dig some more. That Yes, without professional or scientific claims, as indicated in the title of the besieged, it's educational astronomy.
To address these issues should have some prior knowledge. Although we try to maintain a simple language, away from technicalities (whenever possible), some pages of this chapter need a certain level. We could say that the chapter is, at least, for high school students. It is best if you are also interested in physics and astronomy.

Size of the universe

The universe includes all known: matter, energy, space and time. The scales in the universe are so great that we cannot even imagine them.
To get an idea, for each grain of sand that are in the Earth, there are a million stars or more. Our Galaxy is only one of billions of galaxies hundreds.
Even so, all matter in the Cosmos is only a tiny part of the universe. The universe is, above all, an immense space almost empty.
It is impossible to know the exact size of the universe. It could even be infinite, although it seems unlikely. Not knowing what shape has, we can also calculate its size. In addition, still expanding. We only know the size of the visible universe from Earth.
Object Diameter
Earth 12.760 kms
Sun 1,400,000 kms
Solar System 1 month light
Milky way 100,000 light years
Local Group of galaxies 10 million light years
Virgo supercluster 100 million light years
Visible universe 93,000 million light years

Size of the visible universe

The edge of the visible universe from Earth is 46,500 millions of years light in all directions. I.e., a diameter of 93,000 million light years. A light year is 9'46 trillion kilometers.
The calculation is enormous, and yet is only the portion of the universe that we can see. After the Big Bang, the universe expanded so rapidly that part of its light has not yet come up to us and, therefore, we can not see.
But if the universe is only about 13,800 million years, how can there be more distant objects? It is not possible that they are far faster than the speed of light. The answer is the inflation of the universe.
Inflation is the origin of everything: from the space, the time, and all the laws of physics, including the limit of the speed of light. Everything is created on own inflation. So the inflation of the universe is not subject to the limit of the speed of light. Inflation creates new space between objects and takes them away.

Structures of the universe

The matter in the universe is sorted. The force of gravity causes that matter group forming structures. From the simplest, like the stars and solar systems, to the gigantic walls of galaxies.
Even so, the expansion of the universe makes that different structures to radically depart from each other at high speed.
The more distant structures are the largest and oldest. They were formed when the universe was still very young, and help to understand its evolution.

Hierarchy of structures

Smaller structures: are bodies celestial, as planets and stars, and the small groupings, such as our Solar System.
Galaxies: are intermediate structures. They gather families of stars, gas, dust, and dark matter. There are more than 100 billion only in the visible universe, and they can group trillions of stars. Many have a black hole at its Center. Our Galaxy is the milky way.
Clusters of galaxies: are groups of galaxies involved in hot gas. Their diameter reaches several million years light.
Star Wars revolve one around each other, linked by gravity. Sometimes they collide or some are absorbed to others. The milky way belongs to a cluster called the Local Group, comprising 25 galaxies.
Superclusters of galaxies: They are sets of clusters of galaxies. They measure hundreds of millions of light years. They form large layers throughout the visible universe. The Local Group is part of the Virgo supercluster.
Walls: these are the last discovered structures, the most ancient and large universe. They are huge swaths of Superclusters of galaxies.
Sloan great wall measures 1.37 billion years light and is the largest structure that is known.

The great attractor

The Virgo supercluster and the other structures of the visible universe moving towards a mysterious point called the great attractor. Its centre is 150 million years light. It was discovered in the late 1980s and is not yet known what it is, although it might be one structure even more that astronomers call Laniakea ("sky immense", in Hawaiian).

The observable universe

Even with the most advanced technology, we were only able to see a small part of the universe. Observable universe is called, and is the part of the Cosmos whose light has had time to reach us.
The observable universe has a sphere, with the Earth at its Center. So we can see the same distance in all directions.
The boundary of the observable universe is called cosmic light horizon. The objects on the horizon are the farthest we can see. Its light left for us almost since the origin of the universe, 13.7 billion years ago. So that we see them as they were made more than 13,000 million years. Why they are so important to know the evolution of the universe.
But, as the universe expands, in fact these objects are much further away. Currently, they are already 46,500 millions of years light.
Telescope Light type
Hubble Nearby visible, ultraviolet and infrared light
Chandra X ray
Compton Gamma-Ray
Spitzer Infrared remote

Great observatories of NASA

To explore the entire observable universe, NASA put in orbit four space telescopes: Spitzer, Hubble, Chandra and Compton. Each captures a different type of light. Currently, the Compton is no longer operating.

The observable universe at a glance

The part of the universe that we see with the naked eye is called the celestial sphere. It is an imaginary sphere, with the Earth in the Center, where the constellations are located. It reaches up to the 2'5 million of years light.
The furthest that can be seen is the neighboring Andromeda Galaxy, and the two satellite galaxies of the milky way: the small and the large cloud of Magellan. Everything else belongs to our Galaxy, the milky way.

Types of particles in the universe

All the matter that exists in the universe is composed of particles. Each particle type serves a different function.
The interaction between the different types of particles makes it possible the universe as we know it.
There are two kinds of particles: fermions and bosons. The fermions form the mass of matter. Bosons are responsible for applying to this mass the four fundamental forces: electromagnetism, strong nuclear force, weak nuclear force and gravity.

Elementary particles

Elementary particles are parties or smaller portions in which matter can be divided.
The elementary fermions are the leptons and quarks:
- Quarks: come together in groups of three to form larger, such as protons and neutrons particles.
- Leptons: are very light, like electrons, muons and neutrinos particles.
Elementary bosons are photons, gluons, and others:
- Photons: responsible for electromagnetism.
- Gluons: deal with the strong nuclear force.
- Bosons W and z: responsible for the weak nuclear force.
- Graviton: responsible for gravity, but still it has not been never.
- Higgs Boson: responsible for the particles to have mass. It explains all the matter we see, and why it is called "the God particle".

What are hadrons?

When several elementary particles come together, cahnge composite particles called hadrons.
Composite fermions are the Baryons. The best known are the protons and neutrons. Composite bosons are the Inns. The best known is the pion. The Hadron Collider at CERN is a very important particle physics experiment.
Scientists from around the world participate in it. It accelerates the particles (hadrons) to almost the speed of light and makes them to collide to see how they behave. Through these experiments, the CERN seeks information about undiscovered types of particles, the composition of the universe, its origin, and how acting forces among themselves.

The matter in the universe

Matter is everything that has mass. All matter consists of particles. They are as tiny pieces that come together to form what we see.
Although they also form another type of matter that we cannot see, the dark matter. In fact, most of the material that makes up the universe is dark matter.
Everything that has mass, however small that is, emits gravity. Even ourselves. In the Cosmos, matter is attracted by the gravity. It brings together and shape from small molecules to planets, stars, and the great Galactic clusters. Gravity holds matter together. Even so, most of the matter not concentrate in galaxies, but in the immense intergalactic space.

The visible matter

The part of the matter that we can see is only 5% of the composition of the universe. The visible matter is called ordinary matter or baryonic matter.
Ordinary matter consists of atoms. It can be in four States: solid, liquid, plasma and gasesoso. It goes from a State to another to gain or lose heat. Most of the visible matter in the universe is in the plasma state, since it is that shape the stars.

Dark matter

In the universe there is another matter, which we cannot see. It is invisible or dark matter. The fourth part of the known universe is dark matter, although some sources estimate that it is up to 80%. This means that much more quantity of dark matter that visible matter.
Dark matter does not emit or reflect any light. Not release any radiation, neither visible nor invisible. For this reason we cannot see it. But we know that it exists because if it emits gravity, and our technology detects it. Its gravity is so great that it moves the great Galactic clusters.
The composition of dark matter remains a mystery. Although it is believed that it could be made up of neutrinos and other particles still unknown.

Cosmic radiation

All the visible objects in the Cosmos, from the planets to the Superclusters of galaxies, emit some sort of radiation. This radiation is energy that travels through space. The light we see is a small part of that filing, which our eyes can perceive.
There are (i.e. known) two types of cosmic radiation: the electromagnetic radiation and cosmic rays.

Electromagnetic radiation

It is the energy emitted by celestial bodies and travels through space in the form of waves. It moves at the speed of light. Electromagnetic radiation is, along with the matter, the other major component of the Cosmos. It includes radio waves, microwaves, infrared waves (heat), visible light, ultraviolet rays, x-rays and gamma rays.
Our atmosphere protects US from the electromagnetic radiation of high energy: gamma rays, rays X and part of the ultraviolet rays. If not, life on earth would not be possible.

Cosmic rays

Corpuscular radiation or cosmic rays are not waves but charged particles of energy, such as neutrinos. Stars emit showers of particles that pass through the area at high speed. Cosmic rays carry the burden of higher energy that is known in the universe.
Our Sun emit cosmic rays that reach the Earth. The Earth's magnetic field diverts most. But they are so powerful that a fraction manages to enter the atmosphere and go through it. Sometimes, the charged particles pass to the upper layers of the atmosphere by the Poles, and form auroras.

Shape of the universe

The shape of the universe is an issue very important for cosmology, since the final destination of the own universe depends on the form that has. However, it is still impossible to find out.
The shape of the universe depends on its density, i.e. the amount of mass and energy. The problem is that we don't know which size has the universe or how much energy and matter there are in total. So we can not calculate its density.
Einstein's theories posed three possible ways: closed, open, or flat. Although the shape of the universe continues to be an enigma, the majority of scientists believes that it is almost flat.
Type of universe Density Form Final destination
Closed universe High Spherical Collapse and Big Crunch
Open universe Low Saddle Cooling and Big Chill
Flat universe Critical Flat Slowed down expansion

The shape and fate of the universe

The universe can have three possible ways:
Closed universe: if there is too much matter and energy, the density is very high. The universe curve inward and will shape of sphere. It will be a finite universe. Gravity will be stronger than the expansion, all matter will be grouped, and the universe will collapse. This end is called the Big Crunch.
Open universe: the density of matter and energy is too low, the universe is curve outward. It will take the form of a saddle. It will be an infinite universe, infinite expansion. Gravity will be so weak that there can be no stars, planets, or even atoms. Matter will be separated and will disintegrate until being reduced to elementary particles. The universe will cool and die. This end is called the Big Chill.
Flat universe: if the amount of matter and energy is adequate, the density will be balanced. It is what is called the critical density. Then the universe is flat. Gravity and expansion will be in balance. The universe expands, but more and more slowly.
Today it is believed that the universe is almost flat, but there are still many doubts, it is shown that the universe is expanding ever faster, and this seems like a contradiction with the theory.

Models of universe

Traditionally, the cosmology imagine the universe as a linear model. I.e., a single universe with a beginning and, probably, an end.
For the linear model, the Big Bang is the beginning of everything: space, time, physical laws and all matter and energy. There is a single universe and all that encompasses exite. But the linear model has contradictions and does not resolve all the issues. For this reason, other models were raised.
Einstein proposed the cyclic universe model. For the cyclic model, the universe is born and dies infinite times. There isn't a single universe, but infinite. Each universe is between a Big Bang and the next cycle. The universe expands and contracts, so that it starts with a Big Bang and ends with a new Big Bang. Whenever a universe dies, a new one begins.

Membranes or Branes universe

String theory is a cyclic model called "Branes universe". According to this model, each universe is a membrane or membrane. There are endless branes. The branes vibrate and sometimes collide. When two branes collide a new Big Bang and is born another universe.

Parallel universes

The model of parallel universes, there are many universes at the same time. Although there are at the same time, they are independent and it is impossible to move from one to another. Its physical laws are different and some may only have life. The best-known models of parallel universes are universes bubble and the multiverse.
Universes bubble: new universes are born of others that already exist. A new universe can be born at any time and place of the Cosmos. There is an inflation of space, such as that created our universe, and a new universe begins inside another.
Multiverse: is a consequence of the laws of probability in quantum mechanics. It proposes that if time is infinite, all odds just to be satisfied. Each probability is fulfilled in a parallel universe. So 'I' would have parallel universes with exactly identical and parallel universes with another completely different "I". It is an idea that is difficult to understand.


A worm hole is a tunnel that connects two points in space-time, or two parallel universes. Never has been one and is not proven to exist, although they are mathematically possible.
They are called so because they resemble a worm that goes through an Apple inside to the other end, rather than take it out. Thus, Wormholes are shortcuts in the fabric of space-time. Allow unite two very distant points and arrive more quickly than if you had the universe at the speed of light.
According to the theory of general relativity of Einstein, Wormholes can exist. They have an entrance and an exit in different space or time points. The tunnel that connects them is in hyperspace, which is a dimension that is produced by a distortion of time and gravity.
Einstein and Rosen raised this theory to study what was happening inside of a black hole. Why are also called Einstein-Rosen bridge.
There are two kinds of worm holes:
- Intrauniverso: connecting two points away from the Cosmos.
- Interuniverso or Schwarzschild holes: connect two different universes.

Can you travel in time?

One thing is that there are holes of worm and quite another to be used for travel in space and time.
The novel "Contact", Carl Sagan proposed a trip through a wormhole. This led to much believe it possible. But it is only science fiction. Scientists believe that a worm hole has a very short life. Opens and closes quickly. Matter would be trapped in it or, although I got out the other end, could not return. Obviously, we could not choose where we would take.
According to general relativity, it is possible to travel to the future, but not to the past. If you could travel to the past, we could alter history, for example, making that we were never born. It would be impossible.


Always, the human being has been interested in knowing and understanding the universe and the laws that govern it. From different points of view, philosophy, Religion and science have tried to answer these questions. The part of the science that studies the universe in its entirety is called Cosmology.
Cosmology scientifically addresses issues such as the composition of the universe, its structure, shape, origin, evolution and final destination. To do this, it serves of astronomical observation and scientific knowledge. Other sciences such as astronomy, physics, and mathematics are useful for cosmology. Technological advances are critical in the development of modern cosmology.

Modern Cosmology

Modern Cosmology begins around the year 1700. Then there is the idea that all the stars of the milky way formed a grouping in the midst of a universe much greater. Earlier, it was believed that our Galaxy was the entire universe.
In century XX Cosmology is marked by two major advances: Einstein's theory of relativity , and the inflationary theory. Relativity unifies the space, time and gravity, and change the vision of the fabric of the universe. The inflationary theory poses that space has expanded quickly after the Big Bang.
Today, the study of Cosmology is focused on particle physics. The main instrument of current Cosmology are not telescopes, but large particle accelerators. Looking for particles that help solve mysteries such as the composition of dark matter, what happened in the first moments of the universe, or if there are other dimensions that we don't see.
Published for educational purposes authorized by: Astronomía: Tierra, Sistema Solar y Universo

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