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. AGNow 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?
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