Science a GoGo's Home Page Forums General Discussion Physics Forum Why was entropy low in the early Universe?

Currently, our best understanding of the fundamental nature of reality comes from quantum field theory.

Fields vibrate in various ways, and we perceive these vibrations as particles.

There must be a lower limit to the wavelengths, because the energy of a wave is inversely proportional to its wavelength. If there were no lower limit, energy would go to infinity, and on the way would collapse into a black hole. The Planck length provides this lower limit.

An effective upper limit is set by the size of our co-moving patch. It is not that larger wavelengths are not possible, but they are effectively constant throughout the observable Universe.

Should we consider the state space of the Universe as consisting of vibrations in all the quantum fields that are larger than the Planck length, and smaller than the size of our co-moving patch?

If the entropy of the Universe is linked to the number of allowed wavelengths, then the maximum allowed entropy would have been very much less when the Universe was little more than the Planck length across.

If, for the moment, we ignore gravity, could it not be argued that the entropy of the Universe is constant?
It has always equalled the maximum allowed entropy.

Now I could write a book about this and we could dive through some lovely QFT but how about I just answer it in a much simpler way.

Pull up the page on wikipedia about Entropy and you will get this entropy, is proportional to the natural logarithm of the number of microstates.

At the big bang everything is in very close proximity and "almost" homogenous, as such it has very few microstates. I once saw Brian Cox series do this really well for layman, with a bucket of sand and we say that has low entropy. Now tip it on the ground and spread it out there is your high entropy.

Every bucket of sand is just itching to get out

We can put approximate numbers on the microstate counts the current number for the earliest point we can go to in the big bang is 10E88 and today we are at about 10E104 (http://www.mso.anu.edu.au/~charley/papers/EganLineweaverApJOnline.pdf). That is the revised up from the previous estimate of about 10E102.

Tell me if you are happy with that and we can then talk about QFT and your wavelength issue, which is going to be fun to try and make it understandable to you

I avoided mentioning S = k. log W in the hope of minimizing the maths in this thread.

Apart from all the maths in your link, which I'm doing my best to ignore, I'm OK so far.

Running short on time and lots on at the moment. Looks like they will announce the detection of gravity wave merger of two black holes on thursday, conference is all booked in.

Will get back to this ASAP but might be a few days.

Hopefully you will return with lots of news.

Well we have a black hole merger ringing down to a Kerr black hole in the spy details release with the speed of gravity transfer at c. I use assume this is hard to keep secret now with a large number of telescope re-tasking. The angular resolution of Ligo still leaves an very big area of space to search.

So lets see we have direct confirmation of black holes, that they can merge, that the result is a spinning black hole and the speed of gravity transfer is c ... so GR is holding in the most extreme conditions. No interest at all

I believe "I am", everything else is open to question.