The temperature of the Universe at Plank time was about 100 million trillion trillion kelvin.
Is it possible to know (or predict) the temperature of the universe at exact t=0 ? Also was Entropy=0 when t was = 0 ?
Thanks
I’ll have a stab since you have no responses.
Firstly many of the equations break down at t=0. So while following the graph we might see temperature tending towards infinity as we roll the clock back, but at the same time other values are jumping to minus infinity, or Not a Number, so what kind of state was the universe actually in? It’s better just to say that our physical models can’t be run at t=0.
With the entropy thing, the universe apparently started out in a minimum entropy state. I know intuitively this doesn’t make much sense because “super high temperature explosion” doesn’t seem like the limit of order. But this is just one of those situations where the pop sci understanding of “entropy” and the analogies often used, may be misleading.
OF course a lot of this assumes that the size of the universe at time zero is also zero. No reason to think that, it is just a parsimonious use of assumptions. If the size (volume) is zero the energy density is undefined. Its size might not have been zero. We might have been bouncing back from a big-crunch - in which case.there is not a clear definition of time zero either, nor the minimum size of the universe. The universe might have been squeezing though a tiny tiny wormhole from another universe. In which case time zero, or size is again not clearly defined. No shortage of ideas. About all we can say is that if we use our currently - known to be incomplete - laws of physics we don’t know and can’t know. It might be undefined, it might have a number, it might in some sense be infinite, it might even be zero.