We explain what the universe is, how it was created and how it is composed. What are its general characteristics and the solar system?
What is the universe?
We call the universe the totality of the different forms of matter, energy, and momentum as well as the totality of space and time. Based on the big bang theory, it is assumed that the universe is constantly expanding not only in the three spatial dimensions but also in the fourth dimension, time.
The universe is subject to constant physical laws, many of which are verifiable on Earth, while others remain unknown or still under investigation.
The distances in the universe are so great that they must be measured in light years. A light year is the distance that light travels in one year and is equivalent to 9.5 trillion kilometers.
See also: List of Galileo Galilei’s discoveries.
Characteristics of the universe:
1. Origin and age of the universe
Currently, the most widely accepted theory about the origin of the universe is the so-called big bang theory. This theory states that about 14 billion years ago, all the matter in the universe was concentrated at a single point. This matter had a very high energy level, which led to a tremendous explosion (“big bang”) from which the universe emerged.
2. Observable universe
The universe we know is only a part of the whole universe. The entire universe could be infinite. However, the observable or visible universe is finite. It includes all matter and all energy that has been acting on us since the beginning of the entire universe. A number of features of the observable universe are already known:
- Its size is about 46.5 billion light years in all directions from Earth. It is important to know that the Earth is not at the center of the universe, but is merely our vantage point from which we can delineate the observable universe.
- Observations suggest that the shape of the observable universe is flat.
- Contrary to what we might think, scientists have found that the universe is a very bright ocher color called “Cosmic Latte.”
3. Composition
It is estimated that the universe is 73% dark energy, 23% cold dark matter, and 4% atoms.
- Dark energy. It creates a pressure that accelerates the expansion of the universe. Although there is no experimental evidence for its existence, it is the way to explain the expansive motion of the universe within the framework of the standard model of cosmology.
- Dark Matter. A type of matter that does not emit electromagnetic radiation.
- Atoms. They are the most elementary particles of ordinary matter. The earth, inanimate objects, organisms and even man are made of atoms.
4. Galaxies
The largest organization in the universe is the galaxies. They can be classified according to their shape:
- Elliptical galaxies. They have a defined internal structure with little interstellar matter. Since their stars are in a very advanced stage of evolution, they are considered the oldest type of galaxy.
- Spiral galaxies. They have a central core from which spiral arms radiate. In the core there are a large number of stars and almost no interstellar matter. In contrast, interstellar matter is abundant in the arms, as are young stars. Within the observable universe, 75% of galaxies are spirals. A subtype of spiral galaxy is the barred spiral galaxy, which has only two arms. An example of this is our galaxy, the Milky Way.
- Lenticular galaxies. They are thought to be spiral galaxies that have lost their interstellar matter and arms, leaving only the nucleus.
- Irregular galaxies. These are galaxies that do not have a fixed configuration like the previous three types.
5. Stars
Stars are balls of gas whose brightness is due to the nuclear reactions of the gases that form them. The first gas to undergo nuclear fusion is hydrogen because it is the simplest element, with a single atomic molecule containing a single proton and neutron and a single electron. When the hydrogen is used up, nuclear reactions occur with other heavier substances, and the star becomes a red giant.
The Sun is the closest star to Earth, and the gas in which nuclear fusion takes place is hydrogen. This can be seen from the color of the light.
6. The Planets
Planets are bodies that have so much mass that their gravitational pull creates a spherical body. Planets orbit a star and move in an orbit. No two planets have the same orbit.
7. Solar system
It is the planetary system in which the earth is located. All human exploration of the universe to date has been limited to the solar system. The center of the solar system is the sun, whose gravitational pull has created the orbits of eight planets (in order of proximity to the sun):
- Terrestrial planets. Consists of rock and metal.
- Gaseous planets. Consists of ice and gases.
8. Satellites
These are the celestial bodies that revolve around the planets. Just as the Earth has a satellite (the Moon), other planets in the solar system have satellites, with Jupiter having the largest number with 63 satellites.
9. Asteroids and comets
They are rocky objects orbiting a star. Unlike planets, they can intersect with other celestial bodies when describing their orbit. Their size is very different.
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