The degree of order in the Universe

[revo74]

In a video on YouTube, Roger Penrose says the Universe was not chaotic, but extremely ordered/organized and special at its original state. He said the Second Law of Thermodynamics tells us that as time passes our Universe becomes more disordered, therefore, if we were to go back in time things would be more and more organized. He said the figure describing this initial state would be at least 1^123. The video is bellow, begin at 4:50:



My questions are:

a. Is he right and if so has that figure been confirmed?
b. Is he suggesting that the percentage of the Universe was more organized in its initial or even early states than it is now or that there simply was less entropy. The reason why I ask this is because when I asked someone why the Universe had low entropy at the beginning he responded:

"The initial low entropy at the beginning of the universe can have two reasons: the universe at that time was highly complex, but the entropy was low, or the universe at that time was very simple, such that it couldn't hold much entropy in the first place. As you learned in thermodynamics, entropy is an extrinsic property — it depends on the size of the system. The smaller the system, the less entropy it can hold. What was true at the beginning of the universe? It was small, and as such, could hold only a tiny fraction of the entropy it can hold today."

Please elaborate further if you wish.

Thanks!

 

[ibysaiyan]

I am interested with this finding too.
* Subscribes*

 

[Ken G]

a. Is he right and if so has that figure been confirmed?

I couldn't say, I would begin to try to gainsay Penrose.

b. Is he suggesting that the percentage of the Universe was more organized in its initial or even early states than it is now or that there simply was less entropy.

The latter. The early universe was highly homogeneous and thermalized, so there wasn't much organization there.

The reason why I ask this is because when I asked someone why the Universe had low entropy at the beginning he responded:

"The initial low entropy at the beginning of the universe can have two reasons: the universe at that time was highly complex, but the entropy was low, or the universe at that time was very simple, such that it couldn't hold much entropy in the first place. As you learned in thermodynamics, entropy is an extrinsic property — it depends on the size of the system. The smaller the system, the less entropy it can hold. What was true at the beginning of the universe? It was small, and as such, could hold only a tiny fraction of the entropy it can hold today."

I don't know, but it sounds like this person has an incorrect understanding of the meaning of "extrinsic." Entropy is extrinsic because it depends on the amount of stuff, not because it depends on the volume. If you adiabatically expand a gas against a piston, its entropy stays constant, no matter how "big" the compartment gets.

Indeed, this raises an important point about entropy-- if the cosmological principle were strictly true on all scales, so things stayed homogeneous as the universe expanded, then the entropy of the universe would not increase at all (ignoring details like recombination and reionization). The reason it does increase is that we have gravity, and the gravitational instability, so when things clump together, a lot of heat is let out of the genie's bottle. So it's just the opposite of what you might be imagining-- the "organization" results in an increase in entropy, as gravitational potential energy is converted into heat or light. The maximum entropy is achieved by dropping everything into black holes.

 

[Chronos]

Another way of putting it is the universe used to be smooth, and now it is chunky.

 

[revo74]

Another way of putting it is the universe used to be smooth, and now it is chunky.

So when Penrose talks about the geometry of the Universe, do you think this is what he is referring to?

 

[Chronos]

Yes. The geometry of the universe is strongly affected by gravity and matter is the source of gravity. Shortly after the big bang matter/energy was evenly spread throughout the universe. It has since become increasingly concentrated in small areas surrounded by increasingly vast amounts of empty space.