On Thursday, January 23, 2020 at 12:37:21 PM UTC-7, Brent wrote: > > > > On 1/23/2020 2:40 AM, Alan Grayson wrote: > > > > On Wednesday, January 22, 2020 at 9:03:55 PM UTC-7, Alan Grayson wrote: >> >> >> >> On Wednesday, January 22, 2020 at 8:54:37 PM UTC-7, Brent wrote: >>> >>> >>> >>> On 1/22/2020 6:38 PM, Alan Grayson wrote: >>> >>> >>> >>> On Wednesday, January 22, 2020 at 1:34:00 PM UTC-7, Lawrence Crowell >>> wrote: >>>> >>>> On Wednesday, January 22, 2020 at 11:33:04 AM UTC-6, John Clark wrote: >>>>> >>>>> On Wed, Jan 22, 2020 at 12:06 PM Lawrence Crowell < >>>>> [email protected]> wrote: >>>>> >>>>> > *It is then possible to have an expanding accelerated cosmos that >>>>>> is spherically closed.* >>>>> >>>>> >>>>> So if I keep going I will eventually return to where I started even >>>>> though everything is constantly getting more distant from me and is doing >>>>> so at an accelerating rate? >>>>> >>>>> John K Clark >>>>> >>>> >>>> For an accelerated expansion of the sphere there is a cosmological >>>> horizon that one can't cross. in other words, the sphere will keep >>>> expanding faster than you can ever go. Think of the scene in the movie >>>> "*The >>>> Shining*" with Jack Nicholson where the hotel hallway telescoped away >>>> faster than he could run. >>>> >>>> LC >>>> >>> >>> I don't think it depends on acceleration. As long as the universe >>> expands, even at a constant rate, at some distance, the distance between, >>> say, an Earth observer, and some terminal point along a line of sight, will >>> exceed 300,000 km (the distance light travels in one second) and points >>> beyond that will keep increasing the increment every second, creating a >>> cosmological horizon that light cannot cross. >>> >>> >>> That's not quite right. Light can cross it just fine. But a photon >>> crossing it toward us, can never reach us. This is how the Hubble boundary >>> differs from a black hole event horizon. >>> >>> Brent >>> >> >> Good point. TY. AG >> > > Now I'm not so sure. ISTM, the photons that never reach us, never cross > the event horizon. They're emitted in a region receding faster than the > SoL, so they can never cross it. AG > > > Sure they do. If galaxy Z is at our Hubble boundary, we're at galaxy Z's > Hubble boundary. Does that mean we can't emit a photon toward galaxy Z? > > Brent >
It's still not clear. Let's say galaxy Z is in our non-observable region and emits a photon in our direction. Since space is expanding faster than light at that distance, the photon isn't traveling fast enough to enter our observable region, presumably where the event horizon is located. AG -- 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/5661d0de-114c-4776-9da2-f39779f994a4%40googlegroups.com.
