How do we know at all what "should" have happened at the big bang?

[questionposter]

So we know that there's matter, and then we know there's anti-matter. How do scientists know just from that when we have no evidence about the big bang itself or before that there should be equal parts of matter and anti-matter or that they should have annihilated each other completely? Yeah, there's less anti-matter, but obviously that's just the result of how matter/anti-matter naturally work. There's just naturally a process where unknown particles create different properties that add up to make only specific things and break down and build up in only specific ways, so where did all these assumptions come from?

[Schrödinger's hat]

So we know that there's matter, and then we know there's anti-matter. How do scientists know just from that when we have no evidence about the big bang itself or before that there should be equal parts of matter and anti-matter or that they should have annihilated each other completely? Yeah, there's less anti-matter, but obviously that's just the result of how matter/anti-matter naturally work. There's just naturally a process where unknown particles create different properties that add up to make only specific things and break down and build up in only specific ways, so where did all these assumptions come from?

 

Basically, we look at what's happenening now, build some rules based on that, then extrapolate them while making as few extra assumptions as possible.

We see some quantities (mass charge parity etc) and see that they are conserved (well we're starting to see that some of them aren't conserved in very extreme circumstances, but that's a whole different story). So in any case where a lack of one of these quantities turns into some of it, we assume its opposite also appeared (so the total stays the same).

This is a gross simplification of something I already don't have a complete grasp of, so don't try and take too much from my words, but this outlines the general process.