Comments on: A new Hawking paper http://www.symmetrymagazine.org/breaking/2008/05/28/a-new-hawking-paper/ extra dimensions of particle physics Tue, 07 Feb 2012 15:22:30 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Extenuating Circumstances – links for 2008-05-31 http://www.symmetrymagazine.org/breaking/2008/05/28/a-new-hawking-paper/comment-page-1/#comment-771 Extenuating Circumstances – links for 2008-05-31 Sat, 31 May 2008 10:30:32 +0000 http://www.symmetrymagazine.org/breaking/?p=213#comment-771 [...] symmetry breaking » Blog Archive » A new Hawking paper Really quite interesting when you get into it: winnowing down the myriad options that current string theory presents into something slightly more usable (tags: hawking physics theoreticalphysics hartle hertog paper noboundary universe) [...] [...] symmetry breaking » Blog Archive » A new Hawking paper Really quite interesting when you get into it: winnowing down the myriad options that current string theory presents into something slightly more usable (tags: hawking physics theoreticalphysics hartle hertog paper noboundary universe) [...]

]]> By: David Harris http://www.symmetrymagazine.org/breaking/2008/05/28/a-new-hawking-paper/comment-page-1/#comment-725 David Harris Wed, 28 May 2008 14:30:36 +0000 http://www.symmetrymagazine.org/breaking/?p=213#comment-725 Scott, the reason I said "essentially flat" and not "completely flat" is partly for this reason. The current spatial extent of the universe is so large that any overall curvature it has is small--small enough that it appears flat in any local volume. As we are not able to easily measure curvature over much larger scales the exact shape of the universe is still unknown and there has been much debate about it. So I'm sorry I can only give a partial answer as the question is still open, but a spatially infinite universe is not required for this theoretical proposal to work and to still match observations. Scott, the reason I said “essentially flat” and not “completely flat” is partly for this reason. The current spatial extent of the universe is so large that any overall curvature it has is small–small enough that it appears flat in any local volume. As we are not able to easily measure curvature over much larger scales the exact shape of the universe is still unknown and there has been much debate about it.

So I’m sorry I can only give a partial answer as the question is still open, but a spatially infinite universe is not required for this theoretical proposal to work and to still match observations.

]]> By: Scott http://www.symmetrymagazine.org/breaking/2008/05/28/a-new-hawking-paper/comment-page-1/#comment-723 Scott Wed, 28 May 2008 13:21:21 +0000 http://www.symmetrymagazine.org/breaking/?p=213#comment-723 You say that this paper describes a universe in which space is essentially flat. How then does the universe manage to have no boundaries? Is infinite spatial extent required? The bounce resolves the issue of a boundary in time at the beginning, and I suppose that expansion forever removes a temporal boundary at the end, so it is only the issue of a spatial boundary that is left. You say that this paper describes a universe in which space is essentially flat. How then does the universe manage to have no boundaries? Is infinite spatial extent required? The bounce resolves the issue of a boundary in time at the beginning, and I suppose that expansion forever removes a temporal boundary at the end, so it is only the issue of a spatial boundary that is left.

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