Roger Penrose - Before the Big Bang

[Sumo]

http://www.youtube.com/watch?v=fJ-D5AUGVcI&hl=de"
http://www.youtube.com/watch?v=inzgHjEVxAc&feature=channel"
http://www.youtube.com/watch?v=WD3BWt85bxA&feature=channel"
http://www.youtube.com/watch?v=YXDSCEX5wE8&feature=channel"
http://www.youtube.com/watch?v=YX30dxKdJkc&NR=1"
http://www.youtube.com/watch?v=aNS_8WTYVuM&NR=1"
http://www.youtube.com/watch?v=6mV6WnA52wQ&NR=1"
http://www.youtube.com/watch?v=LXYLLG7VkoI&NR=1"
http://www.youtube.com/watch?v=br1zHYH2hvA&NR=1"

This is an interesting video lecture by Roger Penrose talking about his Weyl Curvature Hypothesis. I found most of it fairly easy to understand. Maybe if someone can explain to me one thing: He talks about how entropy at the beginning of the universe was low or zero. But he also says (I think) that the background radiation shows thermal equilibrium, and that the early universe was almost perfectly homogeneous. Doesn't this mean that entropy was high?

 

[Finbar]

http://www.youtube.com/watch?v=fJ-D5AUGVcI&hl=de"
http://www.youtube.com/watch?v=inzgHjEVxAc&feature=channel"
http://www.youtube.com/watch?v=WD3BWt85bxA&feature=channel"
http://www.youtube.com/watch?v=YXDSCEX5wE8&feature=channel"
http://www.youtube.com/watch?v=YX30dxKdJkc&NR=1"
http://www.youtube.com/watch?v=aNS_8WTYVuM&NR=1"
http://www.youtube.com/watch?v=6mV6WnA52wQ&NR=1"
http://www.youtube.com/watch?v=LXYLLG7VkoI&NR=1"
http://www.youtube.com/watch?v=br1zHYH2hvA&NR=1"

This is an interesting video lecture by Roger Penrose talking about his Weyl Curvature Hypothesis. I found most of it fairly easy to understand. Maybe if someone can explain to me one thing: He talks about how entropy at the beginning of the universe was low or zero. But he also says (I think) that the background radiation shows thermal equilibrium, and that the early universe was almost perfectly homogeneous. Doesn't this mean that entropy was high?

I think the idea is that because one constrains the weyl cuvature to some value(zero?) this means that despite the universe being in a thermal state it still is in a very special state so the entropy is low. But it does seem confusing.

 

[George Jones]

I think the idea is that because one constrains the weyl cuvature to some value(zero?) this means that despite the universe being in a thermal state it still is in a very special state so the entropy is low. But it does seem confusing.

Penrose thinks that gravitational entropy is low for uniformly distributed matter and high for clumped matter. See

https://www.physicsforums.com/showthread.php?p=1800223#post1800223
https://www.physicsforums.com/showthread.php?p=1577616#post1577616.

 

[Haelfix]

Maybe I'm confused.. Who disagrees with that? That clumping increases entropy has been standard lore and textbook for a long time now. In the cases we can actually calculate in, that's always been the case.

 

[humanino]

That clumping increases entropy has been standard lore and textbook for a long time now.

Penrose goes further than just that. He identifies the relevant degrees of freedom for gravitational entropy as the Weyl curvature tensor. As pointed out in the thread linked above by George, with a cyclic model for the Universe, he needs the entropy to be constant basically. So if I understand anything to his claim, the entropy flows to the gravitational field, and it takes an enormous change in thermodynamical entropy to make up a small change in the Weyl curvature so you get a very long process to transfer in this direction, while according to him when the Universe becomes conformal and undergoes a transition to the "next big bang", it takes literally no time since there is no reference for any kind of clock.

 

[jquark]

met a man from cambridge today, live in kansas city.

 

[Naty1]

Here's a update/explanation to this concluded thread:

http://en.wikipedia.org/wiki/Weyl_curvature_hypothesis