One of the most interesting topics for discussion and reflection is the idea that our reality, our Universe, may not be the only version, a schedule of events. Perhaps there are other universes, with different versions of us, different stories and outcomes of events, not the same as ours. As for physics, this topic is also extremely interesting from a scientific point of view. Here's what science actually says about whether it might be true or not.
The universe, as far as the most powerful telescopes can see (even in theory), is huge, massive and large. Including photons and neutrinos, it contains 1,090 particles stuck together and grouped into hundreds of billions or trillions of galaxies. Each of these galaxies contains about a trillion stars (on average), and they are all scattered across space in a sphere 92 billion years in diameter, when viewed from our position. But despite what our intuition tells us, this does not mean that we are in the center of a finite universe. In fact, all the evidence points to the exact opposite.
The reason the universe seems finite to us - the reason we can't see everything outside a certain threshold - is not because the universe is finite in size, but because the universe has existed for a certain time. If we understand well what the Big Bang is, everything was like this: the Universe was not constant in space and time, it evolved from a more homogeneous, hot, dense state into a more disparate, cold and diffuse modern state.
And so we got a rich universe teeming with many generations of stars; super cool background, Big Bang afterglow; galaxies scattering the faster the further they are. The limits of what we see are set by the distance that light has traveled since the Big Bang.
But this does not mean at all that there is no other universe outside of the area available to us. In fact, we have every reason to believe that the universe can be practically infinite. Observationally, we can measure several different interesting quantities, including the spatial curvature of the universe, how homogeneous and smooth it is in terms of temperature and density, and how it has evolved over time.
It turns out that the Universe is practically flat spatially, homogeneous, and outside of it, most likely, there will be exactly the same Universe as ours, stretched for hundreds of billions of years in all directions, which we will no longer see. But if you go back in time, rewind history before the Big Bang, you can find something even more interesting. Before the Big Bang of the Universe, there was a different stage.
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This stage, the period of cosmological inflation, describes the phase of the Universe, which was filled not with the matter and radiation we are used to, but with the energy inherent in space itself: in this state, the Universe was expanding exponentially. That is, the expansion did not occur at a certain speed, but rather unfolded like a folded sheet of paper - two, four, eight, sixteen, thirty-two times, and so on.
Since this expansion was not only exponential, but also rapid, the "doubling" occurred with an interval of 10-35 seconds. That is, when 10-34 seconds have passed, the universe has become 1000 times larger; 10-33 seconds have passed - the Universe has become 1030 times larger (or 100010); 10-32 seconds passed - and the Universe became 10,300 times larger, and so on. Exponential expansion is good not because it happens quickly, but because it is inexorable.
Now, obviously, the universe did not always continue to expand in this way, because we are here, which means inflation should have ended and gave rise to the Big Bang. You can imagine inflation starting at the top of a flat hill and slowly rolling down like a ball. As long as the ball stays near the top and rolls slowly, inflation continues and the universe expands exponentially. As soon as the ball rolls down into the valley, inflation ends and energy dissipates. The energy inherent in space itself is converted into matter and radiation. We are moving from inflation to Big Bang.
Before we move on, there are a few important things to note:
- Inflation is not a ball, not a classical field - but rather a wave that spreads over time, like a quantum field.
“This means that as time goes on, as more and more space is created by inflation, certain areas are likely to see the end of inflation and others to see it continue.
- Areas where inflation has ended give rise to the Big Bang and our Universe; in others, inflation continues.
- Over time, due to the expansion dynamics, no two areas where inflation has ended will be able to interact or collide. In between, there will be areas of continuing inflation that will push the former apart.
It is worth noting that we do not know much about this inflationary state, so we are faced with many uncertainties and opportunities:
- We do not know how long the inflationary state lasted before it ended and led to the Big Bang. The universe can be either not much larger than what we see, or much larger, or even infinite.
“We don’t know if the regions where inflation ended are the same or are very different from our own. It is likely that there is an unknown physical dynamics that leads to the fact that all fundamental constants - particle masses, interaction forces, the amount of dark energy - are the same for all regions where inflation has ended. It is also possible that there will be different physics in different areas.
And if these universes are all the same, speaking of the laws of physics, and the number of these universes is truly infinite, and the many-worlds interpretation of quantum mechanics is quite correct, does this mean that there are parallel universes in which everything happened in the same way as in our Universe, not counting one tiny quantum result?
In other worlds, everything could happen in exactly the same way as in ours, except for one tiny detail, because of which your life took a completely different path …
- When did you choose to work overseas instead of staying in the country?
- When did you stand up for the girl and did not give her offense?
- When did you kiss her goodbye, and didn't just let her go?
- When, at some turning point, something prevented you from losing her?
Just think: what if there is a universe for each of the possible outcomes of events? If the probability of the existence of such a universe is not zero, and the number of such worlds is infinite, then everything is possible? For this alone, many "ifs" have to happen. The inflationary state had to remain not just long, but endless.
Thousand factorial: all numbers from 1 to 1000, multiplied among themselves
But there are not 1000 particles in the Universe, but 1090. Every time two particles interact, the result is not one - a whole quantum spectrum of results. There are many more possible outcomes in the universe than (1090) !, and this number is many more googolplexes than the paltry 1010 ^ 50.
In other words, the number of possible outcomes of particle interactions in any universe tends to infinity faster than the number of possible universes increases due to inflation. Even putting aside such questions as there may be an infinite number of possible values of fundamental constants, particles and interactions, and even postponing questions of interpretation, for example, does the Many-Worlds interpretation describe our physical reality, the fact is that the number of possible outcomes is increasing so rapidly - much faster than just exponential progression - that if inflation really goes on forever, there will be no parallel universe identical to ours.
This means that there can be a huge number of Universes, with other laws and so on. But they are not enough to give us alternative versions of ourselves. What does this mean for you?
That there is no other copy of you anywhere in the world. And there is no future that someone else will choose for you. Therefore, live this life in a way that no one else in all parallel universes would have lived it.
ILYA KHEL