On Thursday, July 23, 2020 at 11:59:59 AM UTC-6, Brent wrote: > > > > On 7/23/2020 4:41 AM, Lawrence Crowell wrote: > > On Thursday, July 23, 2020 at 5:56:32 AM UTC-5 [email protected] wrote: > >> >> >> On Saturday, July 18, 2020 at 6:31:23 AM UTC-6, Alan Grayson wrote: >>> >>> >>> >>> On Saturday, July 18, 2020 at 6:18:28 AM UTC-6, Lawrence Crowell wrote: >>>> >>>> The tortoise coordinates is found from the Schwarzschild metric >>>> >>>> ds^2 = (1 - 2m/r)dt^2 - (1 - 2m/r)^{-1}dr^2 - r^2dΩ^2 >>>> >>>> where for a signal leaving a point near the black hole with ds = 0 >>>> (null path) and propagating radially out, dΩ = 0, we have dt = dr/(1 - >>>> 2m/r) which then leads to >>>> >>>> T = t - t0 - 2m ln|r - 2m|. >>>> >>>> That is the tortoise coordinate. Please look this up to read further. I >>>> can't spend beaucoup time going over this for weeks to come. >>>> >>>> LC >>>> >>> >>> You don't have to. We're done. But you should IMO address Brent's >>> objection, maybe on another thread. AG >>> >> > I don't know what objection you're referring to. LC is just showing why > it takes a distant observer forever to see an infalling object reach the > event horizon of a black hole. > > Brent >
Your words: I wonder about the use of cicumlocutions like "from the perspective of an outside observer". In special relativity it it is often said that a moving object will looked shortened along the direction of motion. But as Terrell pointed out that's not at all how they look. It is more accurate to say that *measuring* a moving a object will show that it is shortened along the direction of motion; the difference being that the measurement corrects for the fact that you want the difference in arrival time of photons that left the ends of the object at the same time (an ill defined concept), instead of the image formed by photons that arrived at the same time. But then I think, why not correct for the Lorentz contraction too in the measurement and arrive at what we might call "the proper length". That's just as "measured" as either of the other two. By the same reasoning, you're really saying the visual impression of a distant observer is that infalling stuff appears to be on the surface of the event horizon. Which is because it takes forever for photons to reach him. But why should he be so naive. He knows what he's seeing is arbitrarily far in his past; so what he should be said to "measure" or "calculate" is that the stuff has already been annihilated at the "singularity" in his reference frame. ----------------------------------------------------- I forget why LC brought up this particular coordinate system. He had some point in response to a comment I made. I'll have to review my comments; maybe that the gravitational field due to a BH, external to the event horizon, has an objective reality. AG > > >> When it comes to GR, you're a genius; no question about it. I wouldn't >> want to waste your valuable time. But consider this; the Schwartzschild >> metric applies to NON-ROTATING masses. Do you really think a massive >> contracting star which forms a BH will be non-rotating? Obviously, it will >> be RAPIDLY rotating, like an ice skater who contracts her arms. Brent also >> had some substantive questions about your model. But I see you prefer your >> illusions than to address his objections. AG >> > > The result is similar, but more complex. The same calculation can be done > for the Kerr solution. It is just a lot more complicated mathematically. > > LC > > -- > 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] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/5b3752f7-55da-4c90-bc8b-11e1b8f42344n%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/5b3752f7-55da-4c90-bc8b-11e1b8f42344n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- 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/59617872-7e76-4316-b238-283b3e324144o%40googlegroups.com.
