In the beginning there was a question mark. And then everything else. The end. We've all heard about the Big Bang theory (I'm talking about the cosmological model now, not about the TV series), but it's important to understand what this theory is and what it isn't. Let me clarify one thing that is accurate, understandable, and ridiculously simple: the Big Bang theory is not a theory of how the universe was created. Record this for the record. Correct people when they are wrong.
The point is, there is a lot of confusion on all sides, and it would be better to keep things simple. The Big Bang Theory is a scientific model like any other scientific model. We believe it is correct because - attention - it is supported by a wide range of evidence.
Since its inception, the Big Bang theory has endured decades of struggles among scientists who scratched, fought, kicked in the back, criticized, undermined, bickered, argued, and even called names in an attempt to crush their rivals and prove their alternative was better. Why? Because whoever offers the best scientific paradigm will receive a free trip to Stockholm.
And in the end, nobody canceled the evidence. You know this universe that we are trying to understand. Any new observation is a thunder in broad daylight in the scientific world; two theories may enter, but only one will remain. And what is left after decades of observation? Hint: great.
The evidence began when Edwin Hubble noticed that every galaxy, on average, was flying away from every other galaxy. The universe is expanding. This fact is already quite strong in itself. For millennia, the basic assumption (and there is no one to blame) has been that although things change here on Earth, far in the heavens, everything is relatively unchanged. Stars explode, galaxies collide, but overall, the universe two weeks ago looks like the universe today. Check in a month - the same thing. People thought so.
And they were wrong. The universe today is not at all like the universe yesterday, and tomorrow it will be different. And not only on a local scale.
And if you notice that the Universe is getting bigger every day, you can make a logical effort and guess that a long time ago the Universe was … smaller? Yes? I guessed? And if the scientist inside you has not died yet, as soon as you get to this ridiculous and ridiculous concept, you will think about the consequences and how to test this dubious, at first glance, theory.
The history of the last 14 billion years is the history of density. The universe consists of a bunch of all sorts of things: hydrogen, helium, raccoons, dark matter, cartilage, photons, ferris wheels, neutrinos, and so on. All of this manifests itself in different ways at different densities, so when the universe was smaller, one type of thing could prevail over another, and the physical behavior of these things could govern the course of events.
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For example, these days the universe is mostly dark energy (whatever it is), and its behavior is governed by the universe - in our case, this is a period of accelerated expansion. But a few billion years ago, the universe was smaller and all matter was packed tighter. Because of this density, the ruler of the roost was matter, suppressing dark energy, which was more of a background curtain than the engine of modernity.
(Side note: Dark energy takeover happened almost at the same time as our solar system was collecting itself in pieces, and at the same time the universe was about half the size).
The birth of the dark matter era may not seem particularly dramatic, but the further in time - and the smaller the universe - the stranger things get. Go back more than 13 billion years, when the universe was a thousand times smaller than its current size, and the matter that will one day make up entire galaxies will be so tightly squeezed together that even atoms cannot form. It's so dense that every time the nucleus attracts an electron, a windy, high-energy photon slams into it, knocking the electron away. This is plasma, and once the entire universe was in this state.
Rewind to today, and the remaining light from the era when the universe cooled and expanded enough to allow the first atoms to form continues to shine through us even now. But the universe is older and colder, and these high-energy gamma rays are faint microwaves that create a background that permeates space - cosmic microwave background, relic radiation, CMB.
CMB is not only one of the main signs of the Big Bang (a kind of snapshot of the young Universe), but also a window in earlier times. Even though we cannot perceive the Universe before the formation of the CMB, the physics of that time left an imprint on the radiation background itself. It is important.
The further we go back in time, the less we recognize the universe - it is even stranger than plasma. Go back in time and find that stable nuclei cannot form. Even further, protons and neutrons cannot withstand pressure and degenerate into their components: quarks and gluons. And then everything is complicated.
The Big Bang Theory can be summed up like this: once the entire universe - everything you know and love, on Earth and in the sky - was compressed into a ball with a temperature of a trillion degrees the size of an apple. Or a peach. Or a little grapefruit. Never mind.
This statement sounds ridiculous, but if you had said about this a couple of hundred years ago … You would have been burned at the stake, and not the church, but the scientists themselves. But as crazy as this theory is, we can study this era based on our knowledge of high energy physics. We can simulate the physics of the universe from this early era and trace its consequences to later times. We can make predictions and do science.
In the "age of the peach" the age of the universe was a fraction of a second. Even less than a fraction - 10 ^ -36 seconds or so. From that moment on, we have a rough picture of how the universe functions. Some questions, of course, remain open, but overall we have at least a vague understanding.
The older the Universe becomes, the clearer our picture becomes, but it's scary to even realize that our poor monkey brains have comprehended such a young era of the Universe.
Even earlier, our understanding of the universe is becoming … blurry. Forces, energies, densities, temperatures are getting too high, and the understanding of physics that we have accumulated for centuries is not up to the task. In the very early Universe, gravity becomes especially important on a small scale, and this is already the chambers of quantum gravity, the system of which is still eluding modern physicists. We just have no idea what is happening with strong gravity on a small scale.
Just. Not.
Until these 10 ^ -36 seconds, we simply do not understand the nature of the universe. The Big Bang theory fantastically accurately describes everything that happened after that, but before it is incomprehensible. On a small enough scale, we don't even know if the word "before" made sense. On incredibly tiny scales (even less than you can imagine in theory), the quantum nature of reality rears its ugly head in full force, transforming our friendly space-time into a jungle full of traps, traps and sharp thorns. The concepts of space and time simply don't work on this scale. Nobody knows what's going on.
Of course, there are some ideas - models describing what could "ignite" or "sow" the Big Bang, but at this stage they are purely speculative. If these ideas get support in the form of observations - for example, a special imprint on the relic background - then yes, we can work them out.
If not, then they will remain bedtime stories. As, incidentally, and everything that we can say about what happened before the Big Bang.
Ilya Khel
