The universe we know may be just one of many. This is an idea that is gaining more and more credibility not only in the collective imagination, but among the scientific community. The merit? All about the theory of cosmic inflation, a concept born to explain the expansion of our universe. And today it could provide us with decisive clues to the existence of others.
Cosmic inflation: a revolutionary theory
Cosmic inflation, proposed in the 80s, has become the leading explanation for some fundamental features of our universe. This theory suggests that, in the very first moments after the Big Bang, the universe went through a period of sudden and very rapid expansion.
This idea would explain why the universe appears so uniform and flat on large scales, but it carries with it a surprising implication. Which? The possible existence of multiple universes, or as it is fashionable to say today, of a "multiverse".
From our universe to the multiverse
Cosmic inflation suggests that the process that gave rise to our universe may have repeated itself countless times, creating a multitude of independent universes. Each universe, in practice, would be like a bubble in an infinite ocean of cosmic possibilities.
To those who this idea may seem fanciful, know that it is rooted in solid physical principles. There quantum theory, which governs the behavior of matter on microscopic scales, allows for random fluctuations that could give rise to new universes.
Looking for concrete evidence
How can scientists find evidence of something that, by definition, is outside of our universe? The answer may lie in cosmic background radiation (CMB), the residual light of the Big Bang that permeates the entire universe.
Scientists hypothesize that interactions between our universe and other universes could leave visible “scars” in the CMB. And in 2011, researchers have identified four regions of the sky that could contain these much sought-after traces.
The search for evidence of the multiverse is an extremely complex undertaking. The potential signatures are subtle and difficult to distinguish from other cosmic phenomena. Even if we found these "scars", then, definitively proving that they are the result of interactions with other universes would be an enormous challenge.
Yet the search continues. It continues, driven by the prospect of a revolution in our understanding of the cosmos. If confirmed, the existence of the multiverse would radically change our view of reality and our place in it.
Beyond cosmic inflation: alternative theories
While cosmic inflation is currently the dominant model, scientists are also exploring alternative theories. One of these is the idea of “cyclic universes”, which proposes that our universe is part of an infinite cycle of expansion and contraction.
This theory, like inflation, suggests the existence of multiple universes, but places them at different times, rather than in different “places”. Before this universe there was another, after this universe there will be another and so on. Other theories? We talked about it in a rather complete article, here.
How could the turning point come?
New technologies and observation methods could provide crucial clues. Future space and ground-based telescopes could offer a more detailed view of the CMB, potentially revealing crucial evidence of cosmic inflation and the multiverse. Physicist Sean Carroll is even certain of it: “parallel universes exist, and we will explore them".
Meanwhile, the theory of cosmic inflation and the implications of a multiverse represent an exciting frontier of modern cosmology. The idea that our universe may be just one among infinite others reminds us how much we still have to discover about the fundamental nature of reality.
It makes you dizzy to wonder not only what lies in the depths of our universe, but also what might exist beyond its borders. Cosmic inflation has opened a window into a potentially infinite cosmos, reminding us that in science, as in the universe itself, possibilities are truly limitless.
