The greater the pressure, the slower the universe will go

Pressure, P, is generally known as the Force applied per unit area (why pushing a thumb tack into a surface tends to be more successful, penetrating the surface, than pushing, say... a brick). Interestingly (which they didn't tell me at school, at least) if you multiply the top and bottom by a length, if becomes Energy per unit volume, or energy density.



This in itself is passingly interesting, but only in an incredibally nerdy, physicsy way, which is fine with me - I at least somewhat physicsy. But, as most people know,



Which is true so long as things are moving so slowly that we don't notice. Which most things, nowadays, are doing. If you weren't, then you'd be in trouble. And nothing would work properly, and it'd be all an unbound mess... Not so much fun as pretty much sitting still.

So, mix them all together, and oddly enough;



Where ρ is the density. Actually, it's true except for the speed of light, which, if you're a particle physicist, you can set to one anyways :D

That's amazing, although it makes sense, sort of... Well, okay, not very much to my intuition, so I may have to think about it some more. Anyways, there it is in it's mathematical glory. This probably still leads to a bit of a "so what" statement.

Well, if you increase the density of the universe, the gravitational attraction increases.



That's assuming the universe is spherical, which it... well, sort of is. It's complicated. It goes on forever, but em radiation tends to go outwards, oft from a point. Think that's it. So, if you increase the pressure of the universe, the acceleration due to gravity increases, and so the expansion of the universe decreases. Which is, at first counter-intuative - greater pressure, slows down the expansion...

But there you have it, in mathsy ways, showing that you increase the pressure of the universe, it'll slow down. It's all linked the pressure not actually pushing on anything :)

And I find that all very interesting.