On Sunday, November 12, 2017 at 1:42:13 PM UTC-7, [email protected] wrote: > > > > On Thursday, November 9, 2017 at 4:42:45 PM UTC-7, Brent wrote: >> >> Cosmologist think the universe is spatially flat. That just means >> triangles have interior angles summing to 180deg. It doesn't have anything >> to do with extent. But the universe is not flat in spacetime; it's >> expanding and at an increasing rate. >> >> Brent >> > > I don't understand how a flat universe has nothing to do with extent. > > I don't understand the distinction; spatially flat (and therefore > presumably infinite in extent?), but not flat in spacetime. > > Also, when it was discovered that the expansion is accelerating, did the > solutions of the field equations which allowed tunneling from a vacuum and > presumably automatically came with a positive CC (indicating expansion), > also automatically come with a spatially flat (and presumably infinite in > extent) geometry? Hard to grasp how a universe emerging from a vacuum could > start out spatially flat and therefore IMO infinite in extent. > > TIA. >
I must have committed some unforgivable crime. I am just not sure what, exactly, it was. I wrote to Ned Wright and Lawrence Krauss, asking how a universe of finite age could be infinite in spatial extent. Including you, Brent, I am 0 for 3. I suppose the answer could be that it tunneled out of the Multiverse, and was infinite in spatial extent at that initial time. Hard to imagine such an event. > >> On 11/9/2017 3:10 PM, [email protected] wrote: >> >> IIUC, the difference is huge. In the former case, the universe is open, >> spatially infinite with infinite mass (assuming a nonzero mass distribution >> on large scale everywhere), whereas the latter is closed, finite in spatial >> extent and mass. But I notice that most cosmologists claim the universe is >> *flat*, as in mathematically flat. Are they just speaking loosely and >> really mean the universe is ASYMPTOTICALLY flat? I find it contradictory >> for a universe which is finite in age, to be truly mathematically FLAT. TIA. >> -- >> 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 [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/d/optout. >> >> >> -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
