Nobody can go back and start a new beginning, but anyone can start today and make a new ending. -Maria Robinson
In parts one and two, we covered the very beginning of the Universe as we know it. Specifically, we talked about inflation, which is the process that sets up the Big Bang. Inflation — to recap — expands the Universe exponentially fast, driving the matter density to zero and stretching the Universe flat like a balloon getting blown up supremely fast.
But inflation ends, and when it does, all of that stored (i.e., potential) energy that was being used to expand the Universe now gets converted into matter and energy.
This moment — when the Universe fills with energetic stuff — is the beginning of the hot Big Bang, and the Universe as we recognize it.
Well, almost as we recognize it. At this moment, the Universe has an incredibly hot temperature. Typically, we measure temperatures in Kelvins. Liquid nitrogen boils at 77 Kelvin, room temperature is about 300 Kelvin, and the surface of the Sun is about 5700 Kelvin. By comparison, at the beginning of the Big Bang, the temperature is at least 1015 Kelvin and up to (but not more than) 1029 Kelvin!
For comparison, the hottest part during the hottest time of a Supernova (the hottest explosion in the Universe) is only about 1011 Kelvin, or at least 10,000 times cooler than the Big Bang.
So what does our Universe look like? Imagine taking all of the matter (all 1080 atoms or so) in the Universe, all of the photons (about 1090, more or less), all of the neutrinos (about another 1090), and smashing them into a volume the size of your thumbnail.
That’s right, the Big Bang is a time back when the Universe was squished into a region that made it about 1070 times denser than you are right now. Or rather, the most conservative estimate of the Big Bang involves that. If you want to go to the other extreme, the most fantastic estimate is that all of that matter and energy is concentrated into a volume the size of a single proton.
Only, instead of three quarks in there, there would be something like 1090 of them.
Want to know what’s even crazier? There is just as much antimatter as there is matter right after the big bang! For every electron flying around, there’s an anti-electron flying around; for every quark there’s an anti-quark, and for every subatomic particle you can dream up, there’s it’s anti-particle in equal abundance.
And do you know how much of it there was? About a billion times more matter and antimatter than exists (combined) of both of them today.
A lot of people like to start the clock on the Universe imagining that it started as a singularity. As we’ve discussed before, there’s absolutely no reason to think this must be true. But if you insisted anyway and defined that time as t=0, the conservative (lowest energy) estimate for when this Big Bang occurs would be when the Universe is 10-10 seconds old, and the fantastic (highest energy) estimate would be when the Universe is 10-38 seconds old.
And that’s the beginning of our Universe: tiny, young, hot, and full of everything. The whole point of telling this story — what I call the greatest story ever told — is to understand how we got from this point, the very beginning, to where we are today.
So enjoy this step that takes us into what most of us call “our Universe”, and come back later for part four, where we’ll talk about how to get rid of all that pesky antimatter and leave us with the right amount of matter for you and me!