On Wednesday, September 11, 2024 at 1:26:13 AM UTC-6 Quentin Anciaux wrote:
Chatgpt: The reason distant objects eventually recede faster than the speed of light (c) is due to the continuous and large-scale expansion of the universe. As long as the expansion rate is positive (which it is, and even accelerating due to dark energy), the space between us and sufficiently distant objects will eventually increase faster than c. This isn't because these galaxies are moving through space faster than light, but because the space between us and them is expanding at such a rate. *Can you prove this mathematically based on geometry? AG * In cosmology, we describe the expansion of the universe in terms of the Hubble parameter. For any galaxy at a distance greater than a certain threshold (the "Hubble distance"), the expansion of space itself causes the galaxy's recessional velocity to exceed the speed of light. This is a result of general relativity and the way space expands, and it doesn’t violate any physical laws because it’s the space itself that’s expanding, not the motion of objects through space. So, the model guarantees that distant objects will eventually recede faster than c simply because the expansion rate is continuous and increasing with distance. The farther a galaxy is, the faster it appears to move away due to the expansion of the space between us. Hubble's law: The farther away a galaxy is, the faster it appears to recede from us. For galaxies beyond a certain distance, this speed will exceed the speed of light. No violation of special relativity: It’s important to note that no object is moving through space faster than light; it’s the expansion of space itself that causes this apparent superluminal recession. Observable consequences: Once a galaxy is receding faster than the speed of light, its light can no longer reach us, which is why we eventually lose sight of galaxies beyond the observable universe. Le mer. 11 sept. 2024, 09:20, Quentin Anciaux <[email protected]> a écrit : Le mer. 11 sept. 2024, 09:14, Alan Grayson <[email protected]> a écrit : On Wednesday, September 11, 2024 at 12:41:56 AM UTC-6 Quentin Anciaux wrote: To be clearer, imagine you have points drawn on the surface of a balloon. As you inflate the balloon, the distance between two points increases, even though the points themselves aren't moving across the surface of the balloon. The farther apart the points are initially, the faster they seem to be moving away from each other as the balloon inflates. Similarly, in the universe, the farther away a galaxy is, the faster its recession velocity, but this velocity is due to the expansion of space itself, not because the galaxy is moving through space. Quentin *If we imagine two separated galaxies on the equator of an expanding sphere, the distance between them increases as the sphere expands. But the light from either will reach the other, unless the distance is increasing faster than c. How does your model guarantee that the distance is increasing faster than c? AG * Because the expansion is continuous as long as expansion rate is > 0, sooner or later distant object will receed faster than c. Le mer. 11 sept. 2024, 08:37, Quentin Anciaux <[email protected]> a écrit : Le mer. 11 sept. 2024, 07:39, Alan Grayson <[email protected]> a écrit : On Tuesday, September 10, 2024 at 10:51:22 PM UTC-6 Quentin Anciaux wrote: Le mer. 11 sept. 2024, 00:06, Alan Grayson <[email protected]> a écrit : On Tuesday, September 10, 2024 at 3:50:08 PM UTC-6 Quentin Anciaux wrote: Le mar. 10 sept. 2024, 23:19, Alan Grayson <[email protected]> a écrit : On Tuesday, September 10, 2024 at 2:19:42 PM UTC-6 John Clark wrote: On Tue, Sep 10, 2024 at 3:57 PM Alan Grayson <[email protected]> wrote: *>> Even if you ignore Dark Energy and postulate that the Hubble constant really is constant, every object a megaparsec away (3.26 million light-years) is moving away from us at about 70 kilometers per second. So if you try to look at objects a sufficiently large number of megaparsec away you will fail to find any because they are moving away from us faster than the speed of light.* >* That was in the past. At present, the universe is expanding at about 70 km/sec.* *Galaxies are receding from the Earth at 70 km/sec for EACH megaparsec distant from Earth they are. The further from Earth they are, the faster they are moving away from us, so if they are far enough away they will be moving faster than the speed of light away from us. * *> You're assuming the universe today is infinite,* *NO! I said IF the entire universe is infinite today then it was always infinite, and IF it was finite 10^-35 seconds after the Big Bang then it's still finite today. I also said nobody knows if the entire universe is infinite or finite. * *>* *Hubble's law applies to the past, not to the future,* *What the hell?! * *How about an intelligent reply? Obviously, if the universe is infinite today, it was always infinite. But that's what I am questioning. 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? 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 * 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. Quentin *That's the conventional wisdom but what is the physical mechanism? Hubble discovered that the universe was expanding faster in the past, than in the present. Now its rate of expansion is much slower, allowing us to see many distant galaxies. What is the physical mechanism that will cause its present expansion rate to increase to greater than c* The expansion rate can still be the same or even slow down that my explanationis still valid, no need for the *expansion rate* to change for current objects near the horizon to soon recess at more than c. *You haven't explained anything. You're just repeating what you've heard or read. A long time ago Brent explained it as a purely geometric result of the expansion, but now I tend to doubt that explanation. Specifically, if a galaxy now relatively close and visible but due to the expansion moves, say, into a region where the recessional velocity HAD BEEN some multiple of its recessional velocity when relatively near the Milky Way, why does its recessional velocity increase? AG * Because expansion is everywhere the same, take the inflated balloon example, any two points are receeding faster from each other as the balloon inflate at a constant rate, and again it's not the objects that are going at +c, but the space between those objects that expand. *, so distant galaxies will be beyond our field of view? AG* * John* K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> hwt -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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