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Astrophysicists, like many other scientists, continue to ask fundamental questions. But naturally, despite the progress made in this area, there are things that cannot be explained.
Therefore, we have chosen theories that, although they cannot be directly proven, are the only attempts at explanations that we have and that put all these elements together, in an effort to understand why things are as they are.
In this article we review five such theories:
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Dark matter, as its name suggests, has no light. It does not absorb or emit radiation, so it cannot be seen directly.
But scientists know that it exists because of the gravitational effect it has on other elements and on the structure of the universe.
Many experts believe that dark matter is composed of massive particles that interact very poorly with each other and that is precisely why it has not been detected so far.
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Scientists believe that there is something that counteracts gravitational attraction and also explains something seemingly illogical: the constant expansion of the universe.
Gravity should prevent this. And yet it happens…
Dark energy cannot be detected, and scientists have failed to verify whether it really exists, but it is the only explanation they have formulated.
It is also estimated that this energy represents 70% of the universe.
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To solve some of the riddles of the Big Bang theory, physicists devised a bunch of other theories they called cosmic inflation.
This could explain why the universe expanded evenly and very quickly 13.8 billion years ago, the possible age of the universe.
We can imagine the universe as a sphere that seems to expand equally in all directions.
What scientists could not understand was the uniform temperature in all sectors. How can two distant parts of the universe have the same temperature and density without being in contact?
Cosmic inflation theory could explain this phenomenon. This suggests that those parts were united at first, in fact, and that less than a billionth of a second after the Big Bang, the universe underwent an exponential growth that separated them at a faster speed than light, due to space-time expansion.
It's as if the universe is a deflated balloon that instantly inflated at high speed, expanding matter.
In this expansion, small temperature differences, higher density points were created that materialized in galaxies and groups of galaxies. There were also some gravitational ones predicted by Albert Einstein.
Therefore, physicists cannot explain - because they could not observe it - what formed these sets of stars and where, but a phenomenon such as cosmic inflation can make it clear.
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One of the fundamental questions scientists ask is, "Where are we going?" The general belief is that this depends, in fact, on an unknown factor that measures the density of matter and energy in the cosmos.
If we consider that this factor is greater than unity, the universe would be a sphere. Without the aforementioned dark energy, the universe would cease to expand and tend to contract. And that would cause an absolute collapse.
But because this energy exists, scientists are confident that the universe will continue to stretch to infinity.
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In theory, time always flows. This is explained by entropy, a property of matter that means the degree of disorder in a system. In this case, the disorder of the particles of the universe.
This movement is irreversible, but it raises a new enigma for scientists: why was the universe so orderly at the time it came into being?
If, as other theories have confirmed, there was a large amount of energy accumulated in such a small space, why was the entropy (disorder) so low at the origin of the cosmos?
There is still no answer on this issue.
