On Tuesday, January 14, 2020 at 3:37:22 PM UTC-7, Alan Grayson wrote: > > > > On Tuesday, January 14, 2020 at 11:56:51 AM UTC-7, Alan Grayson wrote: >> >> >> >> On Tuesday, January 14, 2020 at 10:27:27 AM UTC-7, John Clark wrote: >>> >>> >>> >>> On Tue, Jan 14, 2020 at 6:47 AM Alan Grayson <[email protected]> >>> wrote: >>> >>> >>> >>>> > >It is true for a de Sitter universe as a solution of the Einstein >>>>> equations. If the universe is spherical, it will eventually recontract, >>>>> and >>>>> light cannot get right round and back to its starting point before the >>>>> universe recontracts to a point. If the universe is expanding via dark >>>>> energy, even if spherical, light still cannot get round because of the >>>>> expansion. In other words, you can never see the back of your own head no >>>>> matter what the geometry of the universe!!!!! >>>>> Bruce >>>>> >>>>>> >>>> > *Since it's not a perfect sphere* [...] >>>> >>> >>> Because we're talking about curved Spacetime and not curved space and >>> because non-Euclidean geometry must be used (due to that minus sign that >>> sneaks into Pythagoras formula if time is one of the dimensions) it's >>> misleading to call it a "sphere", it's even misleading to call it the >>> surface of a 4D sphere. What we really want to know is it the geometry of >>> the universe is open or closed. >>> >> >> *Hypersphere; closed; if you believe it's age is finite. AG * >> >>> >>> >>>> *> light never exactly returns to its starting point. That's just an >>>> approximation * >>>> >>> >>> That's what happens in a de Sitter universe, its flat and open and you >>> get a de Sitter universe if the universe is not dominated by matter but by >>> the Cosmological Constant, which is probably Dark Energy. >>> >> >> *Since it's not perfectly homogeneous, a beam of light can be bent, this >> way and that way, so it's unlikely to return exactly to its point of >> origin. You know, what we OBSERVE and MEASURE is an expanding universe, so >> an ad hoc insertion of an infinite spatial extent is suspect. AG* >> > > *It's like a leaf on a tree. The leaf is our universe, closed and finite > in spatial extent. It's attached to what I've called "the substratum", > analogous to a tree, possibly infinite in spatial extent and having an > infinite past. Let's call it "the Tree of Life". Our universe is connected > to it, has been since the BB, which is why it's expanding, like a leaf > growing. AG* >
*A fruit tree is a better analogy, since most fruits are approximately spherical, as is our universe (hyper-spherical); observable and non-observable regions. It must be somehow connected to its source or origin, but how that connection manifests is currently above my pay grade. The problem with current models of a flat universe is that the infinity of spatial extent implied, seems like an ad hoc hypothesis, not organically connected with the rest of the theory. AG * > >> Already about 74% of the matter/energy in our universe is in the form of >>> Dark Energy, and as time progresses that percentage can only increase and >>> we'll get closer and closer to a pure de Sitter universe. That's because >>> the Cosmological Constant is a property of empty space, so as the >>> accelerating universe creates more space it also creates more Dark Energy, >>> however the total amount of matter (both regular and dark) remains fixed. >>> And in a de Sitter universe the distance between any 2 non-accelerating >>> points will, given enough time, eventually be moving apart faster than the >>> speed of light. >>> >>> >>>> *> **Let's forget it. These discussions are worthless.* >>>> >>> >>> It appears you are not following your own advice. >>> >>> John K Clark >>> >> -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/e5052199-9914-4a56-bcb1-a78bd7441095%40googlegroups.com.
