This is fascinating - and frustrating. I guess all will become clear one day...

On 7 November 2013 17:22, meekerdb <meeke...@verizon.net> wrote: > On 11/6/2013 7:52 PM, LizR wrote: > > On 7 November 2013 16:33, meekerdb <meeke...@verizon.net> wrote: > >> OK, but that doesn't alleviate the confusion. If anything it makes >> it worse. What exactly can we deduce from the entropy of the observable >> universe being approximately maximal when measured by other means, given >> that the BB apparently places a bound on the entropy that can exist inside >> a given volume? Assuming the universe to be, say, 250 times larger than the >> hubble sphere (for the sake of argument) the BB would say that the maximum >> entropy it can contain is 62,500 times the entropy of the hubble sphere. >> >> >> No it doesn't say that. The BB applies to an event horizon, not just >> any spherical volume. In an expanding universe there is only one specific >> radius where the boundary is moving away at c, and that's an event horizon. >> > > I could have sworn that JB's article in Scientific American said this > applied to *any* sphere. > > > The inequality S<BB may be said to apply to any sphere we can investigate > - because equality is only reached when the sphere is so big that it is > receding at c. > > > The impression I got was that If the sphere isn't an event horizon, > it's because the information within it is less than the BB. > > > That's right. > > > Once you pile enouigh stuff into it to exceed the BB you get a black > hole. Or did I misunderstand what he was saying? > > > No, that's right. But that's applying the BB to a BH. The application to > cosmology and the Hubble sphere doesn't lend itself to same cause->effect > relationship, since the Hubble sphere is expanding and taking stuff in. > But it's analogous. That's why it's so suggestive that it seems satisfy > the BB equality. > > > > I had a look on the fount of all knowledge and it doesn't mention that > the BB only applies to event horizons ... > http://en.wikipedia.org/wiki/Bekenstein_bound > > In fact I think it implies that an event horizon forms when the > information content of the enclosed volume reaches the BB....I think....! > > So my question stands. > >> >> As to what we can deduce from it...that's a good question. >> >> > It would seem to have interesting cosmological implications. (I'm not sure > what they are, though!) Maybe that the hubble sphere is an event horizon - > which I guess it is, from our viewpoint. > > > Yes, it's *defined* as our even horizon. But it's not clear what that > implies. > > Brent > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.