This is the second installement of my how the infinitely small rules the universe. For this one I have choosen a weird subject, galaxy formation. yep I am gonna tell you how the rules of quantum mecanic produce some of the biggest thing there are in the univers. How that for power to the small people?
So here it is:
Curent models for the formation of galaxy stars with a fluctuation in the dark matter uniform background. Good but what does that mean you know? It quite simple, we think that for all intente and purpose the universe if flat, homogeneous and isotropic (flat, well mixted and with no prefered direction in layman's terms), that means things are well pretty much boring. Now, however you can have density fluctuation, that means you have slightly more of a thing in a place then in the other. If that happen with dark matter, since from what we know dark matter only interact gravitationally (by curving space-time) we have a "well" that forms. Everything around being slightly less massives tends to fall into the well. Matter and dark matter alike. So once one of those perturbation collapse you have Hydrogen gas that reach critical density and temperature and you forms the first galaxy and stars (theory aren't sure if the first object are stars or galaxy.. well how do you call a stars that is a million time heavier then the sun?). Now, this could happen a few years after the big bang in theory BUT it doesn't it happens much latter in the univers (around redshift 5-6 or about a 13 Gyrs in the past which is a few hundred million year after the big bang). the big question is why don't the perturbation collaspe sooner? Well there is another thing to consider to have the collapse of a perturbation it must be smaller then the maximum distance that light has travelled since the Big Bang, because anything bigger then that doesn't know it exist yet it is too big. (Kinda like a bureaucratie the minute after you posted your forms). Now, how can you have a perturbation larger then the horizon (the name for that maximum distance), you blow it up. Remember my post about inflation? yep it that, it took small very small fluctuation in space time (the kind of thing quantum mecanic perdict (I told you infinitely small would be in there somewhere)) and blew them up to galactic proportion! If the fluctuation had been larger we might not have galaxy today and if they had been smaller we probably wouldn't have the univers we have today... they had to be in the correct quantum range.
So here you have it, random quantum sized fluctuation coupled with a big increase in size of the universe explain how and when galaxy first formed... amazing ain't it?