On Sun, Jan 26, 2014 at 11:49 AM, Edgar L. Owen <[email protected]> wrote:
> Jesse, > > No. > > First you have a basic misunderstanding of relativistic time in your first > paragraph. External observers DO see objects fall through the event horizon > of a black hole with no problem at all. They don't get stuck somehow to the > surface of the event horizon as you suggest. They accelerate according to > the usual laws of gravitation and fall right through the event horizon at > ever increasing speed. > > The effect you are speaking of is simply that their CLOCKS SLOW (from the > frame of the external observer) as their speed increases but primarily > because of the increasingly intense gravitation, but their MOTION through > the event horizon DOES NOT SLOW from the POV of the external observer. > If by "POV of the external observer" you mean what the external observer would see if they were receiving continuous light signals from the falling observer (rather than talking about what happens in some coordinate system used by the external observer), then you're incorrect, the external observer would see the falling observer inch closer and closer to the position of the horizon but never quite reach it. This is in fact an obvious *consequence* of the fact that the falling observer's clock is seen to run slower and slower and never quite reach the time at which the falling observer crossed the horizon--all observers in relativity always agree about which events coincide at the same local point in space time, so if there are a series of markers hovering above the horizon, all observers must agree about the time on the falling observer's clock at the moment he passed locally next to each marker. Thus if the falling observer noticed his clock read 10 seconds when passing marker A, 20 seconds when passing marker B, and 30 seconds when passing marker C, external observer must agree that these local events coincide. So if the external observer sees the falling observer's clock slowing, so that it takes much longer for it to go from 20 to 30 than it took to go from 10 to 20, that means they must also see the falling observer take much longer to cross from marker B to marker C than he took to cross from marker A to marker B. If you disagree, please explain which part of the argument you disagree with. Do you disagree with the basic principle that all observers agree on which local events coincide, so they all agree on what the falling observer's clock read at the moment he passed locally next to each marker? Or do you disagree that external observers see his clock slowing in such a way that it never quite reaches the time at which he locally crossed the horizon? Or something else? Also, I'm sure it wouldn't be hard to find some references written by physicists saying that external observers would see the falling observer getting closer to the horizon but never quite reaching it. Are you claiming that this is incorrect in the standard understanding of general relativity by physicists, or are you just telling me it's incorrect in your personal theories which disagree with mainstream physics? If the former, would you be open to changing your mind if I could find you some such references? Jesse > > You are confusing the frames.... > > Second for the answer to my question of how gravity can escape the event > horizon see my response to Liz on the Tegmark's New Book thread... > > Edgar > > > > On Sunday, January 26, 2014 10:16:07 AM UTC-5, jessem wrote: >> >> According to general relativity, neither gravity nor electric fields >> actually "come out of" the black hole's event horizon, rather the gravity >> and EM field felt by observers outside the horizon is a sort of frozen >> snapshot of the gravity/EM fields from all the matter that approached the >> horizon in the past. Keep in mind that external observers can never >> actually see anything cross the horizon, instead they see it moving more >> and more slowly as it gets arbitrarily close to the horizon--the redshift >> is continually increasing as it approaches horizon so in practice an >> external observer can't see an object stuck on the horizon forever, but in >> principle you could if you could detect light with arbitrarily huge >> wavelengths, and if light was a classical EM wave rather than being >> quantized into photons. >> >> The Usenet Physics FAQ at http://math.ucr.edu/home/baez/physics/ has >> some good summaries: >> >> http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/ >> black_gravity.html >> >> 'How does the gravity get out of a black hole? >> >> 'Purely in terms of general relativity, there is no problem here. The >> gravity doesn't have to get out of the black hole. General relativity is a >> local theory, which means that the field at a certain point in spacetime is >> determined entirely by things going on at places that can communicate with >> it at speeds less than or equal to c. If a star collapses into a black >> hole, the gravitational field outside the black hole may be calculated >> entirely from the properties of the star and its external gravitational >> field before it becomes a black hole. Just as the light registering late >> stages in my fall takes longer and longer to get out to you at a large >> distance, the gravitational consequences of events late in the star's >> collapse take longer and longer to ripple out to the world at large. In >> this sense the black hole is a kind of "frozen star": the gravitational >> field is a fossil field. The same is true of the electromagnetic field >> that a black hole may possess.' >> >> They then go on to discuss how the picture is altered by virtual >> particles in quantum field theory, but the above is a good explanation of >> how it works with classical general relativity and classical >> electromagnetism. And this entry from the FAQ discusses how in general >> nothing is actually seen to cross the horizon by external observers: >> >> http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html >> >> 'Won't it take forever for you to fall in? Won't it take forever for the >> black hole to even form? >> >> 'Not in any useful sense. The time I experience before I hit the event >> horizon, and even until I hit the singularity--the "proper time" calculated >> by using Schwarzschild's metric on my worldline--is finite. The same goes >> for the collapsing star; if I somehow stood on the surface of the star as >> it became a black hole, I would experience the star's demise in a finite >> time. >> >> ... >> >> 'A more physical sense in which it might be said that things take forever >> to fall in is provided by looking at the paths of emerging light rays. The >> event horizon is what, in relativity parlance, is called a "lightlike >> surface"; light rays can remain there. For an ideal Schwarzschild hole >> (which I am considering in this paragraph) the horizon lasts forever, so >> the light can stay there without escaping. (If you wonder how this is >> reconciled with the fact that light has to travel at the constant speed >> c--well, the horizon is traveling at c! Relative speeds in GR are also only >> unambiguously defined locally, and if you're at the event horizon you are >> necessarily falling in; it comes at you at the speed of light.) Light beams >> aimed directly outward from just outside the horizon don't escape to large >> distances until late values of t. For someone at a large distance from the >> black hole and approximately at rest with respect to it, the coordinate t >> does correspond well to proper time. >> >> 'So if you, watching from a safe distance, attempt to witness my fall >> into the hole, you'll see me fall more and more slowly as the light delay >> increases. You'll never see me actually get to the event horizon. My >> watch, to you, will tick more and more slowly, but will never reach the >> time that I see as I fall into the black hole. Notice that this is really >> an optical effect caused by the paths of the light rays. >> >> 'This is also true for the dying star itself. If you attempt to witness >> the black hole's formation, you'll see the star collapse more and more >> slowly, never precisely reaching the Schwarzschild radius. >> >> 'Now, this led early on to an image of a black hole as a strange sort of >> suspended-animation object, a "frozen star" with immobilized falling debris >> and gedankenexperiment astronauts hanging above it in eternally slowing >> precipitation. This is, however, not what you'd see. The reason is that >> as things get closer to the event horizon, they also get dimmer. Light >> from them is redshifted and dimmed, and if one considers that light is >> actually made up of discrete photons, the time of escape of the last photon >> is actually finite, and not very large. So things would wink out as they >> got close, including the dying star, and the name "black hole" is >> justified.' >> >> >> >> >> On Sun, Jan 26, 2014 at 9:36 AM, Richard Ruquist <[email protected]>wrote: >> >>> Edgar, >>> >>> Electric fields also come out if the BH singularity has a charge. >>> Richard >>> >>> >>> On Sun, Jan 26, 2014 at 8:01 AM, Edgar L. Owen <[email protected]> wrote: >>> >>>> OK, time for THE ANSWER TO MY QUESTION of how gravity can escape from a >>>> black hole.... >>>> >>>> Liz, Brent, and Richard, >>>> >>>> OK, nobody got the answer so I'll explain it myself. It's pretty simple >>>> but still pretty profound and thought provoking.... >>>> >>>> Gravity IS what needs to be escaped. So it doesn't even make sense to >>>> ask how gravity could escape ITSELF. >>>> >>>> There wouldn't even be a black hole if gravity hadn't already escaped >>>> the black hole to create its gravitational effect. >>>> >>>> So what this means is that gravity is the only thing than CAN escape a >>>> black hole because it is gravity itself that creates the gravitational >>>> field that must be escaped! >>>> >>>> Thus gravity, and only gravity, can manifest freely OUTSIDE a black >>>> hole the effects of its INSIDE mass. >>>> >>>> Thus gravity is the only thing that freely COMES OUT of a black hole >>>> through the event horizon, because what stops everything else from coming >>>> out is gravity itself. But obviously gravity can't stop itself from coming >>>> out through the event horizon, because only its already manifesting >>>> presence is what stops everything else from coming out through the event >>>> horizon, but it already must have come out to stop everything else from >>>> coming out... >>>> >>>> Thus before gravity comes out through the event horizon, there is >>>> nothing to stop anything from coming out. Thus gravity can freely emerge >>>> through the event horizon and only by doing so is it able to prevent >>>> anything else from coming out.... >>>> >>>> Hope I'm explaining this clearly? >>>> >>>> Edgar >>>> >>>> >>>> >>>> On Saturday, January 25, 2014 1:29:45 AM UTC-5, Liz R wrote: >>>>> >>>>> On 25 January 2014 16:31, meekerdb <[email protected]> wrote: >>>>> >>>>>> On 1/24/2014 4:41 PM, Edgar L. Owen wrote: >>>>>> >>>>>>> Brent, >>>>>>> >>>>>>> No, my proposed dark matter effect has nothing to do with black >>>>>>> holes. Black holes are caused by accumulations of actual visible matter, >>>>>>> not by the Hubble expansion of space... >>>>>>> >>>>>>> However I do have a question for you. Since gravitational changes >>>>>>> propagate at the speed of light how does the mass inside a black hole >>>>>>> produce gravitational effects outside the black hole? If light can't >>>>>>> come >>>>>>> out how can gravitational effects come out? >>>>>>> >>>>>> >>>>>> You are thinking of gravity as mediated by force particles, like >>>>>> photons mediate the EM forces. But (at least classically) gravity isn't >>>>>> a >>>>>> force, it's just a shape of space and as I responded to Liz, there's not >>>>>> mass in a black hole, no T_u_v term in the Einstein equation. It's a >>>>>> vacuum solution. That's why it doesn't make any different what falls in >>>>>> to >>>>>> create the black hole. The effects outside the event horizon are just >>>>>> that >>>>>> the space is warped there just *as if* the black hole were a massive >>>>>> object. >>>>>> >>>>>> I believe Richard Feynmann was asked the same question (about how >>>>> gravity "escapes" a black hole). Of course gravity WAVES can't escape a >>>>> black hole... >>>>> >>>> -- >>>> 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 post to this group, send email to [email protected]. >>>> Visit this group at http://groups.google.com/group/everything-list. >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>> >>> -- >>> 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 post to this group, send email to [email protected]. >>> Visit this group at http://groups.google.com/group/everything-list. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> -- > 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 post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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