On Friday, May 30, 2025 at 5:01:10 AM UTC-6 John Clark wrote:
On Wed, May 28, 2025 at 5:04 PM Alan Grayson <[email protected]> wrote: *>> The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang. And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44! * *James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe* <https://www.livescience.com/space/astronomy/previously-unimaginable-james-webb-telescope-breaks-its-own-record-again-discovering-farthest-known-galaxy-in-the-universe> *> Does a red shift of 1.8 imply recession at light speed?* *If you're looking at a galaxy that has a red shift of 1.8 then you're looking at how that galaxy looked 10.2 billion years ago, back then it was not moving away from us faster than the speed of light but today it is,* *Applying Hubble's law, the rate of expansion in the early universe was hugely greater than it is today. If that's correct, how can you claim that if 10.2 billion years ago it was not receding faster than light speed (which is possible), but today it is (which seems impossible)? AG* * so although we can see it we could never reach it in a finite amount of time, not even if we could move at the speed of light. And a red shift of 1.8 is the boundary line for that sort of thing. * *> How is that calculated? AG * *The general integral for finding the lookback time tL(z) is complicated and involves calculus because it depends and a lot of things that are changing, it's:* *tL(z)=∫(1+z′)H(z′)1dz′* *where you integrate between zero and the redshift z* *H(z) is the Hubble parameter at redshift z* *H(z)=H0Ωm(1+z)3+ΩΛ in a flat universe with dark energy* *H0 is the Hubble constant today* *Ωm is the matter density parameter* *ΩΛ is the dark energy density parameter* *John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* nxv -- 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 visit https://groups.google.com/d/msgid/everything-list/7d3a0cb7-c469-48ef-89da-7110a0604e1dn%40googlegroups.com.
