Moving at Light Speed: Relativistic Effects Explained

[neopolitan]

The big bang was the "explosion" from a very very small ball of infinitly dense matter, before the explosion was just the ball of matter / energy.

I think you might have the right sort of idea, but there are some serious misstatements.

A very very small ball of infinitely dense matter is indistinguishable from a very big ball of infinitely dense matter. It has infinite mass. If the age of the universe is not infinite, then the volume of the universe is not infinite and if you put an infinite mass in a finite universe the matter is still going to be infinitely dense.

As Dave said, it wasn't matter originally anyway. Nor was the big bang an explosion. Perhaps it is worth remembering that "big bang" was initially a pejorative. It wasn't meant to describe what is now the standard cosmological model, it was meant to ridicule it.

Plus, you say "before the explosion was just the ball of matter / energy" which implies (even if not intentionally) that the "ball" was surrrounded by empty space on top of suggesting that there was a sensible "before". At t=0 (where t is now about 14 billion years), there was nothing. At t=t_pl, a Planck time, there was the entire energy of the universe as tightly compacted as it can be.

Here's where I have to bow to quantum physicists, I suspect that the maximum amount of energy you can fit into one Planck cube (or a Planck volume) is the energy associated with the Planck mass (it is also the energy associated with a photon with a frequency of 1/t_pl). (The wikipedia article on http://en.wikipedia.org/wiki/Planck_energy" says this is "probable".)

So, if I am right, one Planck time after t=0, all the energy of the universe would be in a quite small space (with a radius of about 10^-15). After the second Planck time, it would be a radius of about 10cm (very roughly). This would require the space to have expanded at greater than the speed of light with a very high Hubble constant, but that would be consistent with a Hubble constant which corresponds with the age of the universe (as it does today) and the fact that the edges of the universe would be outside of the Hubble distance for that value of the Hubble constant. (The Hubble distance is the distance away that something has to be to be moving at the speed of light. That makes it the radius of the observable universe.) I also think that other factors would come into play, like gravity (because concentrations of energy resist the expansion of the universe, as do galaxies today) and heat, although this may not figure until you get condensation of matter.

After that, I think you would have something akin to an explosion (to the same extent that quickly blowing up a balloon without it bursting is an explosion), or at least the beginnings of lumpiness in the universe.

Anyway, at Planck time, the energy of the universe was not associated with one photon with a very high frequency (just not possible), nor was it infinitely dense. If the Hubble constant is linked to the age of the universe, then it doesn't make sense to have any before the big bang. (Although, to be as comprehensive as I can, it is not impossible that the Hubble constant represents the age of the universe since the big bang. That just means that the time before the big bang is meaningless, in a similar way that time in an empty static universe would be meaningless.)

cheers,

neopolitan

 

[cragar]

When did time start

 

[madmike159]

At the big bang.So the big bang was t = 0

 

[Dmitry67]

So, if I am right, one Planck time after t=0, all the energy of the universe would be in a quite small space (with a radius of about 10^-15). After the second Planck time, it would be a radius of about 10cm (very roughly).

It always puzzled me, how 10^34 plank distances can be created during 1 plank time...

 

[madmike159]

It always puzzled me, how 10^34 plank distances can be created during 1 plank time...

Well planks length is the distance light can travle in planks time (t_{p}\ =\ 5.3906(40)\ \times\ 10^{-44}\ s), we know the universe is slowing down exponentially but we don't know if it will stop and collaps on its self.