Monday, July 22, 2024

We will never be able to see the beginning of the universe: here’s why


We thought the Big Bang caused everything, then we realized there was something else before it.

Of all the questions you ask us every day in the comments below our posts, one of the most common is: “Where does all this come from?” The twentieth century brought us general relativity, quantum physics, and the Big Bang. All of this is accompanied by amazing observational and experimental successes. All of these things allowed us to make theoretical predictions that we were then able to test. But, at least for the Big Bang, we found an almost uncomfortable compromise, which we still deal with today. The point is that any information about the beginning of the universe no longer exists in the universe in which we live. And we have to deal with it.

The beginning of everything

the big explosion. Credit: NASA

Starting in the 1920s, Edwin Hubble and Milton Humson They decided to measure the distances of some stars and galaxies. But when they combined measurements of the distance and redshift of these stars (so-called Redshiftwhich we talked about here), everything led to a disturbing conclusion: the universe It was expanding. The farther away the galaxy is, the faster it is moving away from us.

what is going on

So, if the universe is still expanding today, this means that the following things must be true:

  1. The universe becomes Less and less denseBecause the amount of matter present occupies increasingly larger volumes;
  2. Universe The weather is coldThe light inside extends to longer wavelengths than ever before;
  3. Unbound galaxies gravity To others They move away More and more.
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If the universe is expanding, cooling and becoming less dense, this means that in the distant past it was smaller, hotter and denser. This led astronomers to assume that originally all matter was concentrated in one point: that remains We found cosmological evidence thanks to the discovery of the cosmic microwave background radiation in the mid-1960s. What’s left of the Big Bang?

Because we can only go so far in the past

You might think that all this means that you can extrapolate everything that has happened since the beginning of the Big Bang, and perhaps even before that. The universe could have reached infinitely high temperatures and densities, creating a physical state Known for its uniquenessIt is a “point” at which the laws of physics we know are no longer valid. The problem is that there are a number of things we don’t know about the Big Bang (and may never know). Example: What was before the big bang?

What was before the big bang?

We have escaped the theory of inflationWhich postulated that before the Big Bang there was this inflationary state, where the universe had a large amount of energy embedded in the fabric of space itself. Which would then cause the universe to expand dramatically. Once inflation ended, the fundamental energy of space was transformed into matter and energy, giving rise to what we later called the Big Bang.

Wasn’t the Big Bang the beginning of everything?

In theory, it is a plausible solution that the Big Bang alone could not explain. Thanks to data from satellites such as COBE, WMAP and Planck, we understand that only inflation can produce the consequences we know, in line with the things we have observed. But this also means that the Big Bang wasn’t the beginning of everything; But only for the universe as we know it. It’s as if inflation has pressed a “reset” button: everything that existed before expanded so rapidly that all that remained was empty uniform space with quantum fluctuations that would later lead to the hot Big Bang.

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In short, we can Go back in time As much as you want, but the questions will only multiply. We may never be able to answer you, because if that information no longer exists in our world, how would we ever know?

References: Big Think


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