Science Forums 2

[CraigD]

Originally Posted by Little Bang

… let's say what was the BB composed of in the first second[?] …

According to the Big Bang theory, the universe 1 second after the big bang was a ordinary – other than being very hot, and having an extraordinary number of anti-leptons - hot plasma gas. All of the common particles behaved as we usually observe them behaving today: quarks and gluons are confined in hadrons, there are lots of strongly interacting leptons, neutrinos don’t interact strongly with anything, and photons do.

The main difference between the 1 second-old universe and the everyday plasmas we see today in the sun, florescent lights, etc, is that it was much hotter, so hot that protons and neutrons aren’t bound into atomic nuclei, and photons interacting with them to produce such an extraordinary number of lepton/antilepton (mostly electron/positron) pairs that photons and lepton/antilepton pairs are effectively different momentary expressions of the same thing. Like photons in the interior of present-day stars, photons can’t travel more than a short distance without interacting with something, so light in any ordinary sense doesn’t yet exist.

This state of the universe lasts for about 2 seconds, followed by one much like it that last for about 3 minutes.

There are a lot of excellent descriptions of this period, know as the “lepton epoch” because most of the mass of the universe was then in the form of leptons and antileptons. A good summary, with links to others, is the wikipedia article “timeline of the big bang”

Originally Posted by Little Bang

So far I have not seen any of the standard model or QM people give a direct answer.

I’m surprised to hear this, as brief descriptions like mine above are common in popular science books and TV documentaries.

Upon reading this post, I hope that you consider yourself to have seen a direct answer to the question “according to the Big Bang theory, what was the universe composed of 1 second after the Big Bang?”