Moronium 89 Posted April 8, 2019 Report Share Posted April 8, 2019 (edited) In Minkowski Spacetime time is curved and with those curves come things like time dilation, You have added all sorts of math equations to this post, which I didn't really see until now, Vic. But they don't, and can't, prove the point you are trying to make anyway. That's because your initial premise is wrong. In Minkowski spacetime, space is NOT "curved." It is flat. Furthermore, "time" does not even exist in that realm. Only "spacetime" does. Edited April 8, 2019 by Moronium Quote Link to post Share on other sites

Moronium 89 Posted April 8, 2019 Report Share Posted April 8, 2019 (edited) I don't think he was talking about moving clocks; just a group of clocks sitting together and running at different rates. Broken clocks. Not really "broken," because they're all still running. They're just not synchronized, that's all. Clocks can be "out of sync" for any number of reasons, including, but not limited to, the fact that they are moving at different rates of speed. But whether or not two (or more) clocks are synchronized is an entirely different question than whether, because they are not synchronized, "time" has changed. My argument is that "time itself" has not changed at all, just because the clocks don't all display the the same amount of elapsed time during a time interval that is identical for all. Either way, the same amount of time has passed. Time is not different for each clock. Only the clock readings (a function of their mechanical ticking rate) are different. BTW, Popeye, I edited the post (to correct some typos) which you said did not make sense. You're right, it didn't, as originally written. Maybe you can make sense out of it now, though. Edited April 9, 2019 by Moronium Quote Link to post Share on other sites

Moronium 89 Posted April 9, 2019 Report Share Posted April 9, 2019 (edited) No physicist has said this. What physicists say about what signals a distant observer see's and what is really happening are two different things. Awol will tell you that the Atlantic Ocean is 183 miles deep. If questioned about the source of this "information," he will tell you that it's a universally known fact which can easily be confirmed (all while he refuses to confirm it). After repeating this 197 times, he will finally reveal what his immense "support" is. Something like: "Everybody knows there is an Atlantic Ocean." Edited April 9, 2019 by Moronium Quote Link to post Share on other sites

fahrquad 82 Posted April 9, 2019 Report Share Posted April 9, 2019 (edited) In all fairness the Atlantic Ocean is relatively new. It didn't start forming until the break-up of Pangaea around 163 million years ago. https://youtu.be/UwWWuttntio Edited April 9, 2019 by fahrquad Quote Link to post Share on other sites

ralfcis 43 Posted April 12, 2019 Report Share Posted April 12, 2019 (edited) With the photo of the black hole I hope the Penrose and Thorne nuts finally crawl into one. The hole is bigger than our solar system so the nuts think the event horizon is far enough from the center to make gravity very weak out at the horizon. But suddenly there's still an accretion disc out there that is caused by very strong gravity. So that very dumb movie "Interstellar" based on the physics stylings of Kip Thorne was way off. How do Thorne and Penrose keep their jobs? Edited April 12, 2019 by ralfcis Quote Link to post Share on other sites

OceanBreeze 392 Posted April 12, 2019 Report Share Posted April 12, 2019 I knew this BH was Big, but I didn't fully realize just how big until I looked at this size comparison. That is actually scary. I would like to see someone try to approach the event horizon of that monster and land on it! Quote Link to post Share on other sites

TonyYuan2020 2 Posted February 24 Report Share Posted February 24 (edited) &nbsp;All you need to know about black holes to understand these is that no object can ever reach the event horizon of a black hole from a distance, an object falling towards the event horizon becomes increasingly time dilated and length contracted but never reaches the horizon. 1).Given that no amount of time is enough for an object to reach the event horizon of a black hole from the perspective of an observer at a distance, can we accurately say from the perspective of an object falling towards a black hole that an infinite amount of time must pass on the watch of a more distant observer from the perspective of the falling observer before they are able to reach the event horizon? If the answer is yes then although there would be a time on the watch of the falling observer when they reach the event horizon, how is any lifespan of the black hole long enough for an infinite amount of time to pass on the watch of a distant observer from the perspective of the falling observer before they reach the event horizon? If an infinite amount of time has to pass on the watch of the distant observer in the frame of the the falling observer as well as in the distant observer's frame then it never happens. If the answer is no then from the frame of falling observer there is a time on the watch of the distant observer when they reach the event horizon but in the frame of the distant observer that time on their own watch passes and the falling observer still hasn't reached the horizon, they can still accelerate away in this frame but in the frame of the falling observer they're inside the event horizon and can't accelerate away once the distant observer's watch reaches that time. 2).If two observers are falling towards a black hole, one behind the other then can the closer object reach and cross the event horizon from the perspective of the more distant observer before they themselves reach the horizon? If the answer is yes then how does the closer object after crossing the horizon from the more distant observer's perspective then reemerge from inside the horizon if the more distant observer accelerates away before reaching the horizon themselves? If the answer is no then all falling objects must reach the event horizon simultaneously so how could any object ever reach an event horizon if they can't reach it from the perspective of an observer falling in behind them? 3).Gravitation is supposed to be time reversible, it's an attractive force either way. This doesn't hold once an object crosses an event horizon because then that object has to reemerge from inside the event horizon if the arrow of time is reversed and that shouldn't be possible with the arrow pointing either way.&nbsp; Let's sort out the whole process:1. Morey's experiment, at that time, scientists could not explain it with Newton's theory.2. Constant speed of light is applied to Lorentz transformation.3. Einstein put forward the hypothesis that the speed of light is constant and established special relativity. But now we can easily explain the Morey experiment with classical physics, and conclude that it is wrong to keep the speed of light constant. Special relativity is a fallacy under the wrong premise. You can download the derivation paper using Newton's Theory.http://www.scienceforums.com/topic/36469-why-morley-experiment-could-not-observe-the-movement-of-interference-fringe/ Edited February 24 by TonyYuan2020 Quote Link to post Share on other sites

A-wal 154 Posted July 24 Author Report Share Posted July 24 It amazes me how many people still think objects are able to reach event horizons, even people who should really know better.Objects can never reach the event horizon of a black hole from the perspective of distant observers, this is already accepted as fact. This is not because of some trickof perspective, it's because time dilation approaches infinity at the event horizon. The object falling towards it gets increasingly time dilated and length contracted in a way that it never reaches the horizon.The easy way to show from here that they can't reach the event horizon is to simply fast forward to the death of the black hole and they never reached the horizon froma distant perspective so they're still there after the black hole has gone. Still some people will argue that they can reach the event horizon from their own perspective.If we now switch to the perspective of the object falling towards the black hole, yes there is a future time on their own watch when they would reach the event horizon and of course for them time is moving normally, so how are they unable to reach the horizon?An infinite amount of time has to pass on all distant watches before their own watch would reach the time when they would reach the event horizon, because they're heading towards an ever increasing area of time dilation that approaches infinite time dilation at the horizon.They will observe distant watches speeding up but an infinite amount of time could never pass on any of them. From all perspectives the black hole will die before the falling object reaches the event horizon.No lifespan for the black hole is long enough for an infinite amount of time to pass distant watches. This is a coordinate independent truth, it still holds when you switch to the perspective of the falling object. Quote Link to post Share on other sites

Dubbelosix 139 Posted July 24 Report Share Posted July 24 If nothing could reach an event horizon, black holes could not grow. You brought this up before and was challenged and refuted accordingly. Quote Link to post Share on other sites

A-wal 154 Posted July 24 Author Report Share Posted July 24 If nothing could reach an event horizon, black holes could not grow. You brought this up before and was challenged and refuted accordingly.No it wasn't refuted, yes it was challenged by attempts mostly as equally hollow as that one. It's a fact that no object can reach an event horizon from the perspective of an observer at any distance, no amount of time on their watch would be enough. I assume you must know this. Given this universally accepted truth within established black hole physics, how do you reconcile the fact that once the black hole has died from a distant observer's perspective no object ever reached the event horizon? Similarly, how do you reconcile the fact the black hole has limited life span from the perspective of the falling observer (that approaches at an ever increasingly rapid rate as they become increasingly time dilated) and an infinite amount of time has to pass on all distant watches from their own perspective before they reach the horizon? The very simple reason why no object can reach an event horizon is because the death of the black hole will always happen before an infinite amount of time passes on any distant watch. Quote Link to post Share on other sites

Mutex 32 Posted July 24 Report Share Posted July 24 It amazes me how many people still think objects are able to reach event horizons, even people who should really know better. Objects can never reach the event horizon of a black hole from the perspective of distant observers, this is already accepted as fact. This is not because of some trickof perspective, it's because time dilation approaches infinity at the event horizon. The object falling towards it gets increasingly time dilated and length contracted in a way that it never reaches the horizon. The easy way to show from here that they can't reach the event horizon is to simply fast forward to the death of the black hole and they never reached the horizon froma distant perspective so they're still there after the black hole has gone. Still some people will argue that they can reach the event horizon from their own perspective. If we now switch to the perspective of the object falling towards the black hole, yes there is a future time on their own watch when they would reach the event horizon and of course for them time is moving normally, so how are they unable to reach the horizon? An infinite amount of time has to pass on all distant watches before their own watch would reach the time when they would reach the event horizon, because they're heading towards an ever increasing area of time dilation that approaches infinite time dilation at the horizon. They will observe distant watches speeding up but an infinite amount of time could never pass on any of them. From all perspectives the black hole will die before the falling object reaches the event horizon. No lifespan for the black hole is long enough for an infinite amount of time to pass distant watches. This is a coordinate independent truth, it still holds when you switch to the perspective of the falling object. You use infinities a lot, there is no evidence or indication at all that a black hole creates infinities, you also cannot really use 'accepted fact' for black holes, as we know almost exactly zero about them. What we do claim to know is pure speculation, beyond what we have observed, what we observe about black holes is that they have a lot of mass, we see that by how other objects interact locally, and second we know they do not emit visible light (they are 'black'). Apart from those two 'accepted facts', the rest is simply a guess and speculation. Also space contraction is only speculation, there is no observations to confirm that, and many relativists do not think that contraction is an actual effect. If the speed of light is constant in every reference frame (the backbone of relativity), and time 'slows down', that would indicate (along with the redshift) that slower time means longer time (a lower number of longer seconds), and with a constant c and redshift (gravitational shift) that would mean that space (along with time) gets longer and not shorter. So if you are falling towards a massive body (such as a black hole), and your time is relatively slower (longer), then for you to have the same speed of light then the space you are in has to also be longer. As speed is the length of space over a length of time, if your local time is longer (slower), your space has to be longer too. M87 seems to bare this out, it is WAY BIGGER than they expected it to be, which would make perfect sense if the length of space is longer (with time) from mass in accordance with general relativity. You will get infinities from even valid equations if you try to introduce zero's into those equations.. But you cannot use that as an excuse to say therefore the equations are not valid, they are valid, but applied incorrectly. Quote Link to post Share on other sites

Dubbelosix 139 Posted July 24 Report Share Posted July 24 No it wasn't refuted, yes it was challenged by attempts mostly as equally hollow as that one.It's a fact that no object can reach an event horizon from the perspective of an observer at any distance, no amount of time on their watch would be enough. I assume you must know this.Given this universally accepted truth within established black hole physics, how do you reconcile the fact that once the black hole has died from a distant observer's perspective no object ever reached the event horizon?Similarly, how do you reconcile the fact the black hole has limited life span from the perspective of the falling observer (that approaches at an ever increasingly rapid rate as they become increasingly time dilated) and an infinite amount of time has to pass on all distant watches from their own perspective before they reach the horizon?The very simple reason why no object can reach an event horizon is because the death of the black hole will always happen before an infinite amount of time passes on any distant watch.But we have observed black holes eating stars. They tug on nearby objects and there are no actual infinities in nature, we only use them foolishly as boundary conditions. Quote Link to post Share on other sites

A-wal 154 Posted July 24 Author Report Share Posted July 24 You use infinities a lot, there is no evidence or indication at all that a black hole creates infinities, you also cannot really use 'accepted fact' for black holes, as we know almost exactly zero about them.You clearly have very little knowlege of this subject, that's absolutely fine but please don't either pretend or genuinely be under the impression that you do. Black holes do create infinites, that's kind of what defines them in the first place. Time dilation and length contraction approach infinite values at the horizon from the pespect of distant observers, this is a fundamental property of how black holes work. Also space contraction is only speculation, there is no observations to confirm that, and many relativists do not think that contraction is an actual effect.No it certainly isn't only speculation! If the speed of light is constant in every reference frame (the backbone of relativity), and time 'slows down', that would indicate (along with the redshift) that slower time means longer time (a lower number of longer seconds), and with a constant c and redshift (gravitational shift) that would mean that space (along with time) gets longer and not shorter. So if you are falling towards a massive body (such as a black hole), and your time is relatively slower (longer), then for you to have the same speed of light then the space you are in has to also be longer. As speed is the length of space over a length of time, if your local time is longer (slower), your space has to be longer too. M87 seems to bare this out, it is WAY BIGGER than they expected it to be, which would make perfect sense if the length of space is longer (with time) from mass in accordance with general relativity.Oh my. :) No space does not 'get longer', length contraction (along with time dilation) is needed for the speed of light to be constant in all inertial frames, this is very well understood. Velocity is distance over time, to keep the speed of light constant you need time dilation (so it takes less time to cover the same distance) and/or length contraction (so more distance is covered in the same amount of time). It's an equal amount of both that keeps the speed of light c when you change frames. You will get infinities from even valid equations if you try to introduce zero's into those equations.. But you cannot use that as an excuse to say therefore the equations are not valid, they are valid, but applied incorrectly. You're entirely missunderstanding not only the model under discussion but the points of discussion as well. The validity of the equations isn't in dispute and they are being applied correctly, which shows that an infinite amount of time has to pass on the watch of all distant observers before the falling watch reach the time when they would reach the event horizon. This is true both from distant perspectives from that of the falling object, the black hole always dies before an infinite amount of time can pass on distant watches. Quote Link to post Share on other sites

A-wal 154 Posted July 24 Author Report Share Posted July 24 But we have observed black holes eating stars. They tug on nearby objects and there are no actual infinities in nature, we only use them foolishly as boundary conditions.I agree, sort of. There are no infinities in nature and yes they do define boundary conditions, in this case defining the boundary of the interior of a black hole. We definitely have not observed black holes eating anything, that would completely rewrite black hole physics because using gr that is entirely impossible. What we've observed is objects being redshifted out of view as the fall towards a black hole. If we were still able to still see them we certainly wouldn't ever see them reaching the event horizon. This is a very well known and accepted aspect of black hole physics. Quote Link to post Share on other sites

OceanBreeze 392 Posted July 24 Report Share Posted July 24 Moderation Note: merged the new thread on same topic into this one. Stop making threads on the same topic! Quote Link to post Share on other sites

A-wal 154 Posted July 24 Author Report Share Posted July 24 Moderation Note: merged the new thread on same topic into this one. Stop making threads on the same topic!This is really old and went well and truely off topic. Plus I wanted to focus on the simpest argument, this: No lifespan for the black hole is long enough for an infinite amount of time to pass distant watches. This is a coordinate independent truth, it still holds when you switch to the perspective of the falling object. Quote Link to post Share on other sites

OceanBreeze 392 Posted July 24 Report Share Posted July 24 And yet it does happen as we have observed BH eating stars and tearing galaxies apart.Of course, we cannot observe things that are crossing the event horizon as they will be accelerated to light speed.At least, that is what the mathematics says. Apparently, my understanding of BH physics is not as advanced as some of the other people posting here. Therefore, unlike they, who are able to make grandiose proclamations drawn from their vastly superior knowledge, I am forced to examine this question from the viewpoint of humble mathematics (something that Moronium loaths and Awol unfortunately doesn’t understand) A good place to begin, I think, is with the equation for gravitational potential energy: [math]Gravitational\quad PE\quad =\quad \frac { GMm }{ { r }^{ 2 } }[/math] To calculate the total energy in a line from the Swartzchild radius, [math]{ r }_{ s }[/math], to infinity, we just need to integrate that expression with respect to distance [math]{ r }[/math]: [math]\int _{ \infty }^{ r }{ GMm{ r }^{ -2 } } dr[/math] Now, take the result and set it equal to the expression for kinetic energy: [math]\frac { GMm }{ r } =\frac { 1 }{ 2 } m{ v }^{ 2 }[/math] That will yield the kinetic energy of a particle drawn to the event horizon (EH) of a black hole (BH) We know the Swartzschild radius, [math]{ r }_{ s }[/math], of the BH is defined by this expression: [math]{ r }_{ s }=\frac { 2GM }{ { c }^{ 2 } }[/math] So, we can use that fact to modify above equation to get: [math]\frac { 2GMm }{ { c }^{ 2 }r } =\frac { m{ v }^{ 2 } }{ { c }^{ 2 } }[/math] But that is just [math]\frac { { r }_{ s } }{ r } =\frac { { v }^{ 2 } }{ { c }^{ 2 } }[/math] So, [math]{ v }^{ 2 }=\frac { { r }_{ s } }{ r } { c }^{ 2 }\quad and\quad v=\sqrt { \frac { { r }_{ s } }{ r } } c[/math] It is obvious when [math]{ r }_{ s }=r,\quad then\quad v=c[/math] And that is what I needed to know! Objects infalling to the BH will reach the EH moving at the velocity of light and will certainly pass through the EH and enter the BH. I suppose I could stop there as that answers the first question about whether or not objects can fall into a BH (the answer is YES) but there is another question about what the distant observer sees. Photons that are near to any massive source of gravity, such as a BH, will be delayed in their path to a distant observer, and this is called the Shapiro time delay. This is calculated by this expression: [math]c'=c(1-\frac { 2GM }{ r{ c }^{ 2 } } )[/math] Remembering that [math]{ r }_{ s }=\frac { 2GM }{ { c }^{ 2 } }[/math], the Shapiro time delay can be expressed very simply as just [math]v'=v(1-\frac { { r }_{ s } }{ r } )[/math] Substituting for v, which was already calculated to be [math]v=\sqrt { \frac { { r }_{ s } }{ r } } c[/math],We have,[math] v=\left( \frac { { r }_{ s } }{ r } c \right) \left( 1-\frac { { r }_{ s } }{ r } \right)[/math] I am going to substitute x for [math]\frac { { r }_{ s } }{ r }[/math] and differentiate the expression wrt x: [math]\frac { d }{ dx } (v)=\left( \frac { 1 }{ 2\sqrt { x } } -\frac { x }{ 2\sqrt { x } } -\frac { 1 }{ \sqrt { x } } \right) c[/math] Damn! This is getting complicated plus I realize I am wasting my time but having gone this far I may as well finish itSo, setting the derivative equal to zero I should get the value of the ratio of [math]\frac { { r }_{ s } }{ r }[/math] that will yield the max/min values for v, as seen by the distant observer. And that is just 3x = 1, so [math]\frac { { r }_{ s } }{ r } =\frac { 1 }{ 3 }[/math] Substituting 1/3 back into the equation [math]v'=v(1-\frac { { r }_{ s } }{ r } )[/math] and solving for v’ gives v’ max/min as [math]\pm 0.385c[/math] we can safely disregard the minus answer and the 0.385c closely agrees with observation, as has been posted in this thread. My conclusion is that the distant observer will see a maximum velocity of 0.385 c by observing an object in a region of space that is about 3 times the Swartzschild radius distant from the EH, and from there the object rapidly accelerates to a velocity of c as it enters the BH and crosses the EH. The distant observer can never see the object at velocity c crossing the EH due to cosmic censoring (nobody can see this). I suppose people can, and no doubt will, continue to speculate and argue endlessly about this but they can’t argue with the math (unless I totally botched it, which is entirely possible) Plus, the formula I used for the Shapiro delay is probably not exact enough to provide an accurate answer when the photons are emitted from an object that is closer to the EH than a distance 3 times the Swartzschild radius. So, there is still room for wild speculation and unsubstantiated claims to be made! Quote Link to post Share on other sites

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