Electricity is actually made up of extremely tiny particles called electrons that you cannot see with the naked eye unless you have been drinking. -Dave Barry
Welcome back to our series on The Greatest Story Every Told, where we start from before the big bang and come forward in time to get the Universe we have today. (If you’re just joining us, go back for parts 1, 2, 3, 4 and 5.) Last time, we talked about how we made more matter than antimatter (and we clarified some questions). So what does our Universe look like at this point?
Well, the Universe is still full of hot radiation, flying around and slamming into everything, including nearly equal amounts of both matter and antimatter. Nearly equal, but not quite. For every ten billion antiquarks, there are something like ten billion and six quarks, and for every ten billion positrons, there are ten billion and six electrons. And while all of this is going on, the Universe is expanding and cooling as it continues to age. Everything moves away from everything else, just like dots on the surface of a balloon.
Well, what happens as the Universe expands and cools? Things smack into each other far less often, for one, because there’s more space between them in general. And when they do smack into each other, because things are cooling in addition to expanding, they hit each other with less energy. Even though matter and antimatter are constantly running into one another and annihilating, what’s not happening anymore as the Universe ages is that you’re not making more matter and antimatter to replace what you’re destroying; it’s all becoming radiation. In other words, this happens.
And its counterpart, shown below, is no longer happening once the Universe gets cool enough.
So instead of a fiery inferno, where everything is continuously blasted apart mere instants after it’s created,
things are instead coming together a little more calmly. This means when two up quarks and one down quark get together, they can finally, when the Universe is about 10 microseconds old, form a stable proton. And when two down quarks and one up quark get together, they can form a stable neutron.
All told, the matter and antimatter has all annihilated away, and so our Universe is full of the radiation left over from that, and that tiny little excess of matter: protons, neutrons, and electrons. At this point, the Universe is still only one second old, and still hotter than the center of the Sun, but it looks an awful lot more like what you’re used to!
So come back for part 7, where we’ll see if we can’t save these unstable neutrons from disappearing!