Astronomy

The Big Bang theory and the origin of the Universe

The Big Bang theory and the origin of the Universe

The Big Bang, literally big bang, constitutes the moment in which "nothing" emerges all matter, that is, the origin of the universe.

According to this theory (Big Bang Theory, not "big ban" as it is sometimes called), the matter was an infinitely small point and of very high density that, at a given time, exploded and it expanded in all directions, creating what we know as our Universe, which also includes space and time. This happened about 13.8 billion years ago. Theoretical physicists have managed to reconstruct this chronology of events from 1/100 of a second after the Big Bang.

After the explosion, while the Universe expanded (in the same way that when inflating a balloon it occupies more space), it cooled sufficiently and the first subatomic particles were formed: Electrons, Positrons, Mesons, Barions, Neutrinos, Photons and a long etcetera up to the more than 90 particles known today.

Later atoms formed. Meanwhile, due to gravity, matter was grouped to form clouds of these primordial elements. Some grew so much that stars began to emerge and formed galaxies.

History of the Big Bang Theory

In 1948 the American nationalized Russian physicist George gamow modified Lemaître's theory of the primordial nucleus. Gamow stated that the Universe was created in a gigantic explosion and that the various elements that are observed today were produced during the first minutes after the Great Explosion, when the extremely high temperature and density of the Universe fused subatomic particles into the chemical elements.

More recent calculations indicate that hydrogen and helium would have been the primary products of the Big Bang, and the heaviest elements were produced later, inside the stars. Gamow's theory, although elementary and then rectified, provides a basis for understanding the first stages of the Universe and its subsequent evolution.

The matter existing in the first moments of the Universe expanded rapidly. Upon expansion, helium and hydrogen cooled and condensed into stars and galaxies. This explains the expansion of the Universe and constitutes the physical basis of Hubble's law.

As the Universe expanded, the residual radiation of the Big Bang continued to cool, until it reached a temperature of about 3 ° K (-270 ° C). These traces of microwave background radiation were detected by radio astronomers in 1964, thus providing what most astronomers consider confirmation of the Big Bang theory.

Recent measurements of redshift of supernovae, attributed for now to dark energy, they indicate that the expansion of the universe, far from slowing down, is accelerating. The study of black holes and the recent discovery of gravitational waves continue to provide more interesting data. It seems that research on the Big Bang still has a long way to go.

Open or closed universe? Finite or infinite?

One of the great unsolved scientific problems in the expanding Universe model is whether the Universe is open or closed (that is, if it will expand indefinitely or contract again).

An attempt to solve this problem is to determine if the average density of matter in the Universe is greater than the critical value in Friedmann's model. The mass of a galaxy can be measured by observing the movement of its stars; multiplying the mass of each galaxy by the number of galaxies, it is seen that the density is only 5 to 10% of the critical value. The mass of a cluster of galaxies can be determined analogously, by measuring the movement of the galaxies it contains. By multiplying this mass by the number of galaxy clusters, a much higher density is obtained, which approximates the critical limit, which "seems to indicate" that the Universe is closed.

The difference between these two methods suggests the presence of invisible matter, the so-called dark matter, within each cluster, but outside the visible galaxies. Until the hidden mass phenomenon is understood, this method of determining the destiny of the Universe will be unconvincing.

Many of the usual works in theoretical cosmology focus on developing a better understanding of the processes that should have resulted in the Big Bang. The inflationary theory, formulated in the 1980s, resolves significant difficulties in Gamow's original approach by incorporating recent advances in the physics of elementary particles. These theories have also led to such daring speculations as the possibility of an infinity of universes produced according to the inflationary model.

However, most cosmologists are more concerned with locating the whereabouts of dark matter, while a minority, led by the Swedish Hannes Alfvén, Nobel Prize in Physics, maintain the idea that not only gravity but also phenomena of plasma, they have the key to understanding the structure and evolution of the Universe.

There are many sources on the Internet that further develop the Big Bang Theory, starting with Wikipedia itself. We can also feed our curiosity by looking at the topics listed below.

Discover more:
• The Olbers paradox: is the universe infinite?
• What are gravitational or gravitational waves?
• The uniqueness of black holes


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