The conditions that allowed the Big Bang had to do with the Inflation of our proto-universe. Most of the generations that currently inhabit the planet have grown up under the idea that the universe emerged from the Big Bang. From the perspective we knew, this was the beginning of everything and there was no need to wonder further. Although unknowns were flying in the air, the idea of a singular beginning negated the need to ask what existed before the Big Bang.
For decades astrophysicists and cosmologists have been trying to understand how the universe as we know it today emerged. Theories arise and break with previous schemes, but then they stabilize and promote new theories that end up overthrowing them. This is how the Big Bang theory emerged, which has its roots both in the theoretical field and in the observational/experimental field. Knowledge from Einstein’s General Theory of Relativity, as well as studies of black holes, mass, and the universal vacuum, were interwoven to give shape to the puzzle.
An Expanding Universe
But all of them, perhaps the most revealing were those postulated by Alexander Friedmann, who discovered the solution of the isotropic universe. Friedmann came up with the idea that the universe looks the same no matter which way you look. So he postulated his models that took into account a homogeneous and uniform Universe, where each type of energy is contained. As well as matter and radiation.
Two important conclusions resulted from this. The first is that he seemed to describe a universe on enormous scales, where everything looks similar on average, everywhere, and in all directions. And two, Friedmann’s equations also found that the only possible way for this would be that the Universe cannot be static. Rather, it should be expanding or contracting.
Later it was proven that this is true, right now our cosmic home is expanding at great speeds. Then came Edwin Hubble, who first calculated the distances of stars. Then it was learned that they were much further away than anything else in the galaxy. But also, those that were further away were moving away at even faster speeds than those that were closer.
What does all this have to do with the Big Bang? Well, such a force must have come from somewhere that exceeds gravitational limits enough to cause the Universe to continue expanding. Force that came from the explosion of the Big Bang and thanks to which we continue to expand, a fact that eventually implies a universe that is progressively less dense and much colder than in its early stages, where everything was more condensed. And this is where the problems begin to arise.
The Problem of the Big Bang Singularity
Thinking about the Big Bang means thinking about infinite densities and temperatures that once accumulated in an almost zero space to expand in such a way. What is known as singularity. Starting with a singularity where there were arbitrarily high temperatures and densities and arbitrarily small volumes, means that it must have had a perfect configuration in the balance of matter and energy combined within it.
Only in this way would the correct expansion rate be reached for the universe to continue expanding. Not so fast that it becomes much larger than it is, but not so slow that it collapses again. How is the universe we know today so perfectly balanced in matter and energy?
Scientists have been asking the same question for decades, but one thing is certain, understanding cosmology is not an easy task. Thus, many of them appealed to the initial conditions. That is, the initial configuration had the right conditions and the universe was born this way and that’s it. The need to wonder what came before it was negated. But then came Alan Guth to introduce cosmic inflation.
Cosmic Inflation
Cosmic inflation manages to solve some problems that exist in the Big Bang theory. It does so by postulating a period before the hot Big Bang, where the universe was dominated by a large cosmological constant. This phase stretches the flat Universe, gives it the same properties in all directions, and avoids reaching a singularity. Inflation assumes that quantum fluctuations were generated and spread throughout the universe during the period before the Big Bang. In that sense, it makes new predictions about what types of imperfections the Universe would begin with.
The classical theory of physics no longer describes the beginning of the universe, little by little we have been discovering new ways of understanding our existence in the cosmos. Although the hot Big Bang theory helped us make a huge leap in this understanding, it is now no longer part of the beginning of the universe for astrophysicists, who have decided to go even further back from this big explosion.
This story was originally published in Spanish in Ecoosfera
