Conceptual image of the expanding cosmos

Our growing knowledge of the laws of physics has allowed us to rewind the tape of the universe, tracing its evolution back to a fraction of a second after the Big Bang. Here, however, when the sum total of matter and energy coalesces into a ball of infinite density and temperature, the equations of general relativity break down.

As a theory, “The Big Bang did not involve the bang,” wrote physicist Brian Greene in The fabric of the Cosmos. Whatever happened at that moment, let alone before that moment, is anyone’s (well-reasoned) guess—and there’s no shortage of guesses about how the universe began.

What happened before the big bang?

First, a caveat: many experts say that the word “before” misses the mark. It is assumed that there was some pre-existing time separate from the universe, when really time and space may have come into being outside The universe.

In this view, the question – “what was there before the big bang?” – is literally pointless. Stephen Lowe, Oxford philosopher, has suggested in the interviews that what we need is not an answer to these types of questions, but “a kind of therapy, an explanation that will make us realize why it is time to stop asking the question.”

The idea pushes human language and intuition to their breaking point, but we can try to make sense of it with favorite analogy to the late physicist Stephen Hawking: Wondering what happened before the big bang is like wondering what’s south of the South Pole. It is not even accurate to say that there is nothing further south; the point is that the question itself is meaningless. We are trying to define something that simply does not exist.

How did the universe begin?

This answer may seem intellectually unsatisfying. Surely the universe came from something. How could all this astonishing beauty and complexity come from… nothing?

One solution, dating back to Aristotle, is that there was no origin of motion in the universe – it always existed. Newton, Einstein and others of their caliber believed that the cosmos was eternal and static, until astronomer Edwin Hubble discovered in the 1920s that all galaxies were expanding from each other. This implies a starting point, the famous “singularity”.

So where did the singularity come from? Scoffing at Aristotle’s need for a “first cause,” some physicists today respond that our notions of causation are irrelevant in the extreme conditions of the Big Bang. We need to take a closer look at scientific theories about the origin of the universe.

Read more: Could the Big Bang be wrong?

Quantum mechanics solution

Quantum mechanics has shown that even seemingly empty space is filled with fluctuating virtual particles that, through a process known as tunneling, may be able to generate matter. We only see this kind of behavior on the ultra-small scale, but then the universe was the right size.

One prominent proponent of this perspective is Alexander Vilenkin, a cosmologist at Tufts University. in document from 1982written for an audience of professional physicists, he admitted that “the concept of the universe being created out of nothing is crazy.”

However, he argued that only the laws of physics could have produced everything we see around us. (Physicists have even considered whether it is possible create a universe in a lab.)

Like MIT physicist Alan Lightman has described it“the entire universe could ‘suddenly’ appear from wherever things originated in the unfathomable fog of quantum probabilities.”

However, you might suspect that this “nothing”, if it was compatible with the creation of reality as we know it, was still a “something”.

Universe from nothing

David Albert, a philosopher at Columbia University, claimed exactly that: “If what we previously took for nothing turns out, on closer inspection, to have the composition of protons and neutrons, masses and chairs, planets and solar systems, galaxies and universes in it, then it was not nothing and that I could not they were nothing in the first place.

When it comes to understanding the concept of the universe from nothing, there is an important difference between the philosophical Nothing and physically Nothing. Namely, the latter still includes the laws of nature necessary for cosmic genesis.

Even if we accept Albert’s point, however, we’re just kicking the can down the road. Whatever our universe came from, it must also have come from something else (at least according to the sane expectations of feeble human brains).

In other words, it is “turtles all the way down,” as some academics put it. So, in addressing this question, let’s delve into some theories a little less bogged down in philosophy.

The multiverse and eternal inflation

When we try to imagine the Big Bang, the best we can do is imagine an event of extraordinary power and grandeur, the fireworks show that ended them all—or started them all. But what if, from the perspective of an even more expansive cosmological landscape, it was just another Tuesday?

For example, we can be descendants of a larger proto-universe, which constantly gives birth to new ones. This concept, known as perpetual inflationwas developed in the 1980s, primarily by physicists Alan Guth, Andrei Lind, and Paul Steinhardt.

They believe that under the right conditions, quantum fluctuations can cause the outrageously fast expansion of “pocket universes.” This process can continue indefinitely, resulting in a potentially infinite multiverse. Despite the theory’s name, however, inflation can only be eternal in the future, not in the past—how it began remains a mystery.

Theory of the cyclic universe

It is also possible that the Big Bang was not the beginning of our universe, but rather a transition from some earlier state.

It is possible for space to spin endlessly, with each phase ending where the next begins, making the space between the two more of a bounce than a bump. The cyclic universe theory supports the idea of ​​an eternal universe with all its comforting logic (that is, they are not trying to get something out of nothing) while accounting for cosmic evolution.

According to one version of this story, ekpirotic modelour universe began in a collision between two “branes” — unconfirmed theoretical objects that exist in as many as 10 or 11 dimensions, depending on which version of string theory you adhere to.

We are believed to live in a three-dimensional brane that routinely collides with a second parallel brane, the two separated by higher-dimensional space. The energy produced by their encounter causes them to expand, then contract, and eventually reassemble in the next collision.

Read more: Did the Big Bang happen more than once?

° Сofficial cyclical cosmology

Another alternative is conformal cyclic cosmologythe controversial brainchild of Nobel Prize-winning physicist Roger Penrose, who was inspired by the striking similarity between the birth and predicted death of the universe.

Over an unimaginable period of googol years (a 1 followed by 100 zeros), the black holes will absorb every particle of matter, then boil away in a process known as Hawking radiation, leaving behind a sea of ​​massless photons. Surprisingly, this cold, quiet end is mathematically equivalent to the hot, energetic Big Bang—they are essentially the same, suggesting that one could merge with the other.

In 2020, Penrose even claimed to have discovered imprint of a previous “space aeon” themselves, although many physicists are not convinced.

Until scientists find a much-sought-after unified theory that combines Einstein’s gravitational insights with the mind-bending mechanisms of the quantum world, our picture of the big bang is likely to remain unclear.

As strange as these scenarios are, the truth may be even stranger. Meanwhile, luckily for us, physicists like to speculate about how the universe began.

Read more: Scientists are trying to map the multiverse

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