Within the first few minutes following the Big Bang, all of the building blocks of matter in the universe had been made. Fortunately, enough matter was produced to give us the 100 billion galaxies with their requisite 100 billion stars each, the planets, comets and asteroids and so on, because no additional matter was made since this special epoch in cosmic history.
We think the universe arose from what we call the Big Bang. This was a special kind of explosion. If you could magically be there at that time hoping to witness the fireworks and remark on the shape of it (like a mushroom cloud?) you would have been disappointed. This is because the explosion was so large that it incorporated all of space simultaneously. There would be no vantage point clear of the heart of the blast.
In the first thousandth of a second following the Big Bang, the temperatures were so high, about 100 billion degrees, that no matter could exist. The story which leads to us humans would get interesting only when the universe was about one-hundredth of a second old. At this time the first particles started to form out of pure energy with names like electrons, positive versions of electrons called positrons, the nearly massless neutrinos discussed in a previous blog, and a sparse amount of neutrons and protons. There were also particles of light or photons, in abundance. These photons of light, when summed up, roughly equaled the number counts of the electrons, the positrons, or the neutrinos.
Note the various particles mentioned above were created out of pure energy and a short time later, annihilated each other too, releasing a bit of energy each time. These particles had lifetimes so short as to win over the pity of a May fly. To take the example of the electron, in any given fraction of a second snapshot, the electrons, were all being destroyed and meanwhile an equal number were being created, leading a roughly constant number at any given time.
The plot would thicken in about another 14 seconds when the universe was still very hot yet also cool enough for the nuclear reactions producing the elementary particles to start slowing down. Our story now features a losing battle for our main characters: there would now be more particles annihilating each other than reactions creating them. The temperature would fall as well, to only about 3 billion degrees, making such creation reactions less likely.
In another three minutes the electrons, positrons and neutrinos were destroying themselves disastrously fast, yet the minority neutron and protons particles from which you and I are made would remain intact, and by surviving, would start to take the center stage. It is at this crucial point that the first atoms could form, such as hydrogen, deuterium (hydrogen with an additional neutron), helium, lithium, and beryllium. These are the ingredients from which all of stars are made, and from which we humans are made, and all of it was completed in the first three minutes!