On Wednesday, September 11, 2024 at 7:49:22 AM UTC-6 John Clark wrote:
Alan Grayson <[email protected]> wrote: *> For galaxies to fall out of view, they have to moving at greater than c. Now they aren't receding that fast. How will they start moving that fast?* *What the hell? * *> You're applying Hubble's law without thinking what it says. Just because a galaxy is now receding at less than c, how will continued expansion increase that speed to greater than c? AG * *What the hell? Quentin gave the correct answer to both of your questions: * *> "The farther they are the faster they are receding from you, so as they continue to get farther away they receed faster from you till the point they receed faster than c and go out of your horizon". * *Alan, that is something they would teach you on the very first day of an astronomy 101 class if you hadn't already learned it in high school, which makes your previous two questions even more bizarre. You should have at least a little understanding of the basics of classical physics before you start worrying about the subtleties of the metric tensor in General Relativity. * *That's not a proof, just a statement of what he believes. Didn't you ever learn what a mathematical proof is? AG * *> Hubble discovered that the universe was expanding faster in the past, than in the present. * *No it did not. If you're talking about cosmic inflation, that is a hypothesis that immediately after the Big Bang for about 10^-35 seconds the universe expanded at an exponential rate; the idea seems reasonable but it has not been proven. What we know for sure is that Hubble (the man not the telescope) discovered in the 1920s that the universe is expanding, and thanks to a group of astronomers in 1997 we know that for unknown reasons the universe's expansion is accelerating. So what we know for sure is that in the past the universe was expanding *SLOWER* than it is now. * *Very recently there have been some tentative indications that the rate of change of acceleration (the official technical term for that is "jerk") of the universe is not zero but is negative. In other words the universe *might* be decelerating, but of course even if it turns out to be true that doesn't mean the expansion of the universe is slowing down, although that might happen eventually if the deceleration continues for long enough, if it continues for long enough the universe might even start to collapse, but nobody knows if it will because nobody knows what the hell Dark Energy is.* *John* K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> smt -- 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/3120bea5-b771-4ca3-bd44-b0e2e68bea04n%40googlegroups.com.
