Previously, we explored the first three epochs of the synthesis of the universe from the beginning of the Big Bang until 10-12 seconds after it. Remembering that the longer time is around, the more time it takes to make something interesting happen, let's explore the next several epochs.
The Quark Epoch
10-12 to 10-6 seconds
As the universe continued to cool, fundamental particles finally started to emerge. The first of these are known as quarks. These are the building blocks of subatomic particles and certain kinds of quarks are even associated with each of the four fundamental forces. That is to say, at the formation of quarks, the fundamental forces began to be distinctly separated where before they were unified.
The Hadron Epoch
10-6 to 1 second
The next three epochs are characterized by which kind of particle dominated the rest (in number) at the time considered. The first kind of dominant particle formed due to the continuing cooling of the universe. Quarks started to combine to form multi-quark particles known as hadrons. At the same time, antimatter formed (I know that sounds terribly complicated, but we only use the term to describe a certain kind of matter that, when it reacts with the stuff that's currently in our universe, turns into energy in a process called annihilation. That's not so scary, is it?). Further cooling caused anti-hadrons to collide with the hadrons, eliminating most of them. However, since the number of particles was not exactly equal to antiparticles, a residue of what we now call matter stayed behind in the form of hadrons (i.e. if the other kind of matter had been more numerous, we would have called that matter, and the stuff that's in our universe now would be antimatter). Another noteworthy fact -- of course -- is the fact that now a single second has elapsed in the life of the universe.
The Lepton Epoch
1 to 10 seconds
After the hadron/anti-hadron annihilation period, leptons dominated the particle population in the universe. Leptons are also elementary particles (which come in six flavors), but are not quarks. Your favorite lepton is the electron, which is largely responsible for every electrical device that you've ever heard of. Similar to the Hadron Epoch, the Lepton Epoch ends with a large scale annihilation due to interaction between lepton/anti-lepton pairs.
The Photon Epoch
10 seconds to 380,000 years
Well, now you're thinking, "So everything annihilated everything else? What is left?" We need to get a few things straight. The term annihilation refers only to the annihilation of mass. But nothing can simply disappear. When mass is annihilated, it turns into energy. That's what all that E=mc2 business is about, anyways. Annihilated mass turning into pure energy yields an amount of energy equivalent to its mass times the speed of light squared (9*1016, or a whole bunch). That energy is expressed in little packets of energy called photons, which we more commonly call light. Also worth mentioning is that each of the two previous epochs left behind a substantial amount of matter (from which is formed every planet, star, and galaxy in the universe. So there's still stuff out there.
During this epoch, however, light rules the universe. We have an extremely dense concentration of photons that is rapidly (at the speed of light, no less) expanding. Minutes into the epoch (between 3 and 20) is a period known as nucleosynthesis, during which hadrons and leptons start to combine to form tiny pairs. The most common hadron-lepton pair is the friendly little proton-electron system that we call Hydrogen. Close behind it is a double pair (two protons, two electrons) known more commonly as Helium (finally, something we've heard about before).
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We are now hundreds of thousands of years into the history of the universe and we are just getting ready to make life sustaining planets (in just a few hundred million years!). The third Universe Synthesis post will talk about how stars and planets are formed and how the universe came to look like it does today (i.e. no more particle physics).
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