On Wednesday, January 15, 2020 at 4:19:59 PM UTC-7, Alan Grayson wrote: > > > > 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 * >
*Since there's no preferred point in space-time, the connection to the BB must be everywhere, at every point in space-time. 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. >>>> >>> *Why does the total amount of matter, both regular and dark, remain fixed as the universe expands? AG* 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/d35fb1e0-aefc-4afe-a18a-6532f3f96e1d%40googlegroups.com.
