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Natural Science Forum / Physics / Relativity / March 2007A Speed Limit for Massive Particles?
Particles with mass can not be accelerated to the speed of light. This much we accept. Let's take the case of a moon sized object and an observer in a rocket who is stationary with respect to that object. Having nothing better to do, the rocket observer gives the moon a push, all the way up to 0.999c with respect to the initial unaccelerated frame. But after this acceleration event another rocketeer shows up and claims that the moon has not accelerated at all, that it is stationary. He now accelerates the moon up to 0.999c with respect to his previously stationary frame (let this all be in the same direction). This scenario can be repeated ad nausium. Each time the moon is accelerated it is a little faster with respect to that initial stationary frame. Einstein saw this one coming - he recons that anyone can count themselves to be stationary. This means, by extension, that any object can count some other frame as stationary. This means that the speed limit of a moon sized object can be inferred by calculating the fastest frame that can be measured from that moon's surface. That is because the other object could be stationary and the moon could be moving at a great velocity. Thus one can *measure* the maximum speed of an object like a moon by the speed of the fastest object that can be measured from the surface of that moon. Why the surface? Gravitational time dilation may effect the measurement of a space object's speed (though I personally count a gravitational length contraction of space objects as measured from the surface of an object, not everyone seems to concur. The 1919 measurement of light curling around the sun should be sufficient to prove this effect from a purely optical perspective ie the light begins to diverge before it passes by the sun so that from the surface of, say, a neutron star, the width of space objects would appear to be far less because the light from the edges of that object would have deviated inward (assuming the object is, say, a moon, the disc of the moon would have a smaller circumference). But that is all off the topic of this thread...) On the speed limit question, there should be another way that a speed limit can be established. Gravitational time dilation on an Earth sized object is measurable. I assume that time dilation can not be greater than infinite ie photon emitted from that object and detected by a space observer (or never detected, as the case may be) can not have a frequency lower than zero or a wavelength greater than infinite. As the frequency of a beam of light emitted from a planet's surface is already lower, then the maximum speed of the Earth must be lower than, say, a speck of dust that has a much lower gravitational time dilation. In essence I am suggesting that the combination of time dilation caused by gravity and time dilation caused by the relative motion of the object must be mathematically summed in some way and the combination of the two will be greater than the time dilation caused by the object's relative motion alone. Thus the speed limit can be calculated for, say, the Earth or the moon and that speed limit must be lower for the moon than a dust particle and lower for the Earth than the moon. Using this addition logic we come to Black Holes where time dilation is already off the scale (or gamma etc etc - I am just using time dilation as an example of relativistic changes). Thus a black hole can not be accelerated - it can not move from its current spatial location - it stays put. Said in another way - regardless of the mass of a black hole, it would take an infinite amount of energy to move it nowhere. In other words a Black Hole can not acquire relativistic time dilation caused by its relative motion. Thus all observers must be moving relative to the local Black Hole. Obviously I have saved ink by framing conjecture and intuitive reasoning in a "this is so" format ie I have omitted the apologies for thinking until here. Please read the above as a set of questions rather than proposed answers.  SignatureKind Regards Robert Karl Stonjek Dear Robert Karl Stonjek: ... > In essence I am suggesting that the combination of time > dilation caused by gravity and time dilation caused by > the relative motion of the object must be mathematically > summed in some way and the combination of the two > will be greater than the time dilation caused by the > object's relative motion alone. Contributions to spacetime curvature come from two terms, mass and energy. The gravitational mass of the "moon" in your example is unaffected either by its motion, or the motion of other objects. > Using this addition logic we come to Black Holes where > time dilation is already off the scale (or gamma etc etc - > I am just using time dilation as an example of relativistic > changes). It is not "off the scale". An infaller (that left from infinity) will see the Universe distorted, Doppler shifted due to his motion, but not "infinitely blue shifted" as he crosses the event horizon. > Thus a black hole can not be accelerated - it can not > move from its current spatial location - it stays put. BHs have been detected to be moving around their common barycenter with an object they are consuming. David A. Smith > Dear Robert Karl Stonjek: > [quoted text clipped - 10 lines] > is unaffected either by its motion, or the motion of other > objects. A clock on the moon runs slower than an equivalent space based clock. This we know. If you now accelerate the moon up to some great speed, the moon clock will appear to have slowed relative to the space based clock. Are you saying that the moon in motion is excused from relativistic time dilation because it already has gravitational time dilation?? Or is the motional and gravitational time dilation somehow separate? Do we need to have two clocks on the surface of the moon? Please, this is not rocket science. The two forms of time dilation must both contribute to the total time dilation as read on a clock on the surface of the moon when the moon is in motion. We can think of it in a classical thought experiment. Consider an object emitting a signal once per second. Now, this object is moving away from us at some great velocity. Each successive signal has further to travel and so the signal will be detected at greater than one second intervals. This is the Doppler Effect. Now we consider the time dilation caused by the objects relative motion (relativistic time dilation). This means that a clock on the fast moving object is running slower. We now have two cases of measured time dilation - the Doppler effect and time dilation. This is called Relativistic time dilation. Now we add a third component - the mass of the object also contributes to time dilation. Even when the object is stationary with respect to the observer the 1s signal as emitted is greater than 1s as detected by the space observer. As the object moves away we have Doppler effect and as it approaches great speed the relativistic time dilation will also become measurable (though it is present at any speed). What I am saying is that the speed limit for the object must be where the redshift becomes infinite which is going to be below the speed of light. For an approaching object we have the blue shift caused by the Doppler Effect but red shift caused by relativistic time dilation (caused by the objects relative speed) and gravitational time dilation. > > Using this addition logic we come to Black Holes where > > time dilation is already off the scale (or gamma etc etc - [quoted text clipped - 5 lines] > motion, but not "infinitely blue shifted" as he crosses the event > horizon. Schwarzschild's calculation says that time dilation is off the scale. The Schwarzschild radius is r=2GM/c^2 Gravitational Time dilation is gamma=(1-2GM/c^2r)^.5 Thus we can substitute r in the gravitational time dilation equation for 2GM/c^2 if the object is a Black Hole we get gamma=(1-1)^.5=0 A gamma of 1 indicates no time dilation. Robert Dear Robert Karl Stonjek: >> Dear Robert Karl Stonjek: >> [quoted text clipped - 16 lines] > clock will appear to have slowed relative to the space > based clock. ... > What I am saying is that the speed limit for the object > must be where the redshift becomes infinite which is > going to be below the speed of light. No. The speed limit is where you run out of energy to accelerate either yourself or the object. We have driven electrons in excess of 0.99999c. We have bounced photons off of these, to get *very large* boosts in photon energy. > For an approaching object we have the blue shift > caused by the Doppler Effect but red shift caused by > relativistic time dilation (caused by the objects > relative speed) and gravitational time dilation. So do you propose an infinite number of "speed limits" between exactly away and exactly towards? How silly is that? >> > Using this addition logic we come to Black Holes >> > where time dilation is already off the scale (or [quoted text clipped - 16 lines] > Black Hole we get gamma=(1-1)^.5=0 A gamma of > 1 indicates no time dilation. The formula you cite describes what an external observer sees. Since outbound light is "stuck" at the EH, any events that occur there essentially never make it out into the Universe at large. It has nothing to do with observers crossing the event horizon, or "time rate" at the horizon. http://casa.colorado.edu/~ajsh/schw.shtml David A. Smith > > A clock on the moon runs slower than an equivalent > > space based clock. This we know. If you now [quoted text clipped - 10 lines] > excess of 0.99999c. We have bounced photons off of these, to get > *very large* boosts in photon energy. The frequency of the light increases. So what? Running out of energy is a very practical limit, but in principle one has an limitless supply. > > For an approaching object we have the blue shift > > caused by the Doppler Effect but red shift caused by [quoted text clipped - 3 lines] > So do you propose an infinite number of "speed limits" between > exactly away and exactly towards? How silly is that? Sorry, I seemed to have gone way over your head. > >> > Using this addition logic we come to Black Holes > >> > where time dilation is already off the scale (or [quoted text clipped - 23 lines] > or "time rate" at the horizon. > http://casa.colorado.edu/~ajsh/schw.shtml If Black Holes can evaporate, which current theory says they can, then the events inside a Black Hole can, in principle, be observed later on eg as recorded by a clock. Or are you saying that if we can't see it then it doesn't count? The whole of string theory deals with objects that can never be observed, even in principle, so you must think then entire field is irrelevant? The Schwarzschild radius is a formula for calculating the radius of a black hole for any given mass or density of matter. We are more or less inside a Schwarzschild radius (if the universe is finite) or on the event horizon of many (if the universe is infinite). You seem to want to reject any or my ideas in favour of conventional wisdom, even though you seem to have only a tenuous grasp on relativity. There are several ways of looking at the outbound light. One is to consider that it is stuck. But relative to a space observer a clock inside a Black Hole's event horizon never ticks - it is frozen (relatively). So light is never emitted. Time dilation seems to worry a lot of people. When time stops (relatively) at the black hole or the speed of light they want to deny that reality by saying that you can't go that fast or 'who cares what happens inside a black hole if light never escapes'. The depth of this immaturity is boundless. Thank goodness the likes of Feynman and Gellman never allowed such boundaries to daunt them - when quarks were formulated they thought that they could never be observed - by your measure they should have left them alone. Or perhaps it is OK to look at quarks as long as time dilation is not involved? Grow up. Time dilation indicates relativistic changes - it is not the change per se. It is merely convenient to consider one changeable parameter that is common throughout the universe and across both GR and SR and Quantum Physics etc. Wherever there is time dilation there is relativistic changes and these always occur for a reason (except for the uniform expansion of space-time and the creation of the universe in seven days by some bored bearded vagrant). SignatureKind Regards Robert Karl Stonjek Dear Robert Karl Stonjek: >> > A clock on the moon runs slower than an equivalent >> > space based clock. This we know. If you now [quoted text clipped - 15 lines] > Running out of energy is a very practical limit, but in > principle one has an limitless supply. And yet we have found no infinities, such as *you* imagine. >> > For an approaching object we have the blue shift >> > caused by the Doppler Effect but red shift caused by [quoted text clipped - 6 lines] > > Sorry, I seemed to have gone way over your head. You have the moon have different speed limits, depending on whether it is coming towards you or away from you. You are in over *your* head. >> >> > Using this addition logic we come to Black Holes >> >> > where time dilation is already off the scale (or [quoted text clipped - 27 lines] > If Black Holes can evaporate, which current theory says > they can, "dual to a black hole" have been observed to evaporate. So it seems to be solid ground. > then the events inside a Black Hole can, in principle, > be observed later on eg as recorded by a clock. No. No telling when any given particle ingested will come out, in which direction, or in what form. > Or are you saying that if we can't see it then it > doesn't count? It isn't science if we can't measure. > The whole of string theory deals with objects that > can never be observed, even in principle, so you > must think then entire field is irrelevant? They are (finally) working up testable predictions. > The Schwarzschild radius is a formula for > calculating the radius of a black hole for any given [quoted text clipped - 6 lines] > favour of conventional wisdom, even though you > seem to have only a tenuous grasp on relativity. The errors I have seen you make, belittle what your opinion of my skills in and understanding of relativity are. > There are several ways of looking at the outbound > light. One is to consider that it is stuck. But relative > to a space observer a clock inside a Black Hole's > event horizon never ticks - it is frozen (relatively). So > light is never emitted. But never to imagine that events at this mathematical surface control how fast stuff can move... > Time dilation seems to worry a lot of people. When > time stops (relatively) at the black hole or the speed [quoted text clipped - 7 lines] > observed - by your measure they should have left > them alone. You are not qualified to put words in my mouth. It is not science if you cannot measure, if you do not try to find a way to measure. And even if they have not yet detected quarks, they are still looking. > Or perhaps it is OK to look at quarks as long as > time dilation is not involved? Grow up. It is time that you entered my killfile again. You place on others the smelly garments the you yourself have polluted. Goodbye. <plonk> David A. Smith > >> No. The speed limit is where you run out of energy to > >> accelerate either yourself or the object. We have [quoted text clipped - 7 lines] > > And yet we have found no infinities, such as *you* imagine. Infinities are in the math and they represent limits, for instance length contraction becomes infinite as a rod is accelerated toward c, as does the required force to further accelerate it and so on. These infinities aren't seen and are not exceeded, which indicates that they do act as limits. I have pointed out where further limitations might be found. > >> > For an approaching object we have the blue shift > >> > caused by the Doppler Effect but red shift caused by [quoted text clipped - 10 lines] > whether it is coming towards you or away from you. You are in > over *your* head. No, the speed limit is the same - I mentioned the blue shift. The speed limit relates to the relativistic time dilation, not the regular Doppler distortion. I was only showing how various time dilation components DO contribute to the overall time dilation. > > If Black Holes can evaporate, which current theory says > > they can, [quoted text clipped - 7 lines] > No. No telling when any given particle ingested will come out, > in which direction, or in what form. In principle, the events that occur inside the event horizon can be exposed later on. And let's not forget that a Schwarzschild Black Hole can be formed from ANY density of matter and does not require a singularity. > > Or are you saying that if we can't see it then it > > doesn't count? > > It isn't science if we can't measure. Then science stops at the event horizon. Science can not measure the Big Bang nor any of the events up until recently - so they are out to? Science can not measure anything at the speed of light - that is out as well? Science can not measure quarks (until quite recently), so Gell-Mann's work was not science? And the list goes on - it is a long list. I think extrapolation, usually through mathematical inference, has been the stuff of science for a very long time. > > The whole of string theory deals with objects that > > can never be observed, even in principle, so you > > must think then entire field is irrelevant? > > They are (finally) working up testable predictions. By your logic, all earlier string theory work was not science. But there were testable predictions made - the proton would decay by the earlier theories. Experiments in underground water-filled tubs proved that if protons did decay, they would take longer than the theoretical life of the universe to do it. > > There are several ways of looking at the outbound > > light. One is to consider that it is stuck. But relative [quoted text clipped - 4 lines] > But never to imagine that events at this mathematical surface > control how fast stuff can move... There are no events, not in the life of the universe (interval is too short). > > Time dilation seems to worry a lot of people. When > > time stops (relatively) at the black hole or the speed [quoted text clipped - 12 lines] > measure. And even if they have not yet detected quarks, they are > still looking. Quarks have been detected by the secondary products of interactions in accelerators, but have not been detected directly nor is there any real prospect that such a detection could occur. But it was still science at the time the quarks were formulated even though Gell-mann pointed out that direct observation was impossible. SignatureKind Regards Robert Karl Stonjek > A clock on the moon runs slower than an equivalent space based clock. This > we know. You may think you know that, but the rest of us do not. What we do know is that SIGNALS from one clock to the other display a difference in frequency, but there is no definitive way to assign the change to the signals or to the clock (as you implicitly do). Indeed, one can self-consistently consider this either a change in the frequency of the signals, or a change in the tick rate of the clock, or any combination. This is in essence the freedom to select any coordinate system, because to ascribe the observed frequency difference to clock or signals one must assign simultaneity all along the signal path.... > Or is the motional and gravitational time dilation somehow separate? The situation is very much more complicated than your overly simplistic claims. The only way to actually understand this is to COMPUTE the metric for the various situations you consider. In particular, "time dilation" is not additive in any simple sense. > Please, this is not rocket science. The two forms of time dilation must > both contribute to the total time dilation as read on a clock on the surface > of the moon when the moon is in motion. It is nowhere near as simple as you think. > What I am saying is that the speed limit for the object must be where the > redshift becomes infinite which is going to be below the speed of light. "Time dilation" has nothing directly to do with speed limits. Moreover, the "time dilation" of SR is for a SPECIFIC PHYSICAL SITUATION which is different from the situations you are considering. There is no simple way to discuss "time dilation" except for that specific situation (hence my quotation marks). > time dilation within > the event horizin can not increase further because it already at maximum. "Time dilation within the event horizon" has no meaning whatsoever (implicitly you are considering "time dilation" relative to coordinates far away). You cannot discuss "time dilation" when the observer cannot observe the other clock, and the external observer cannot observe any clock at or inside the horizon. You can consider it the other way around -- consider the blueshift of signals from an external clock to an infalling clock that falls inside the horizon. This blueshift remains finite everywhere within the black hole, until the infalling clock is destroyed near the central singularity. Note my change from "time dilation" to BLUESHIFT -- the former is a relationship between a clock and a coordinate system; the latter is a relationship between signals from one clock and another clock. This way I don't need to worry about what local coordinates to use. Blueshift of signals can be directly measured by a single clock (+ detector); "time dilation" cannot. > time dilation is > already at maximum for a stationary Black Hole. How is the additional time > dilation caused by the motion of the Black Hole summed to its intrinsic time > dilation? This is overly simplistic -- "time dilation" is NOT an intrinsic property of an object, it is a RELATIONSHIP between a clock and A COORDINATE SYSTEM (not another clock). Using approximately inertial distant coordinates in which the black hole is at rest, consider the locus where the "time dilation" has some specific finite value (say ratio of frequencies = 10) -- this locus will be a sphere surrounding the black hole's horizon (I assume a Schwarzschild black hole). In distant approximately inertial coordinates in which the black hole is moving uniformly, that locus will not be a sphere; moreover, the difference in synchronization between these and the previous coordinates imply that in this frame when one considers a locus with that same time dilation but SIMULTANEOUS in these second coordinates, the locus is deformed still more. Note that to consider "time dilation" due to motion one must consider the simultaneity in the second coordinates. You have not considered the effects of the difference in simultaneity between these sets of coordinates -- that's one reason why "time dilation" is not "additive" as you implicitly assume (other reasons are that other components of the metric become important in such coordinates, and the metric components are no longer independent of time). IOW: when the second observer looks at the locus having that "time dilation" she finds a DIFFERENT locus than the first observer, because simultaneity in her coordinates is DIFFERENT from simultaneity in the first coordinates. > The speed of light is c as > measured from any inertial frame. I am saying that a complementary > phenomena is that of the Black hole - that the speed of a Black Hole is zero > as measured from any inertial frame. This is just plain false. Moreover, it is self INconsistent (there can be only one universal speed, and c is already universal). And there are no inertial coordinates that cover a universe containing a black hole.... Indeed, there are not even APPROXIMATELY inertial coordinates that include any region where the "time dilation" due to the gravitation of the black hole is significant. There are only APPROXIMATELY inertial coordinates in regions far from the horizon, and all the "time dilations" you consider must be negligible for the coordinates to be APPROXIMATELY inertial. In short, your whole program of attempting to make conclusions based on "time dilation" is nonsense. To properly consider the situations you attempt to discuss requires one to compute the metric components in the various coordinate systems.... Tom Roberts Dear Tom Roberts: ... >> time dilation is already at maximum for a stationary >> Black Hole. How is the additional time dilation >> caused by the motion of the Black Hole summed to >> its intrinsic time dilation? Tom, I *think* Robert is hung up "additive", as if the effects were not: "detected clock rate" = "normal clock rate" * 0.01 (due to curvature) * 0.01 (due to velocity), but as if the contributions were in fact summed-never-to-be-less-than-zero. David A. Smith > > A clock on the moon runs slower than an equivalent space based clock. This > > we know. [quoted text clipped - 9 lines] > system, because to ascribe the observed frequency difference to clock or > signals one must assign simultaneity all along the signal path.... Clocks on Earth run slower than space based clocks. How many references would you like? You don't like the idea that clocks can accumulate asynchrony eg two clocks placed on the moon and in one space. The two clocks on the moon are synchronised (with each other only). I shift one clock from the moon and compare it to the space based clock. The space based clock and the clock shifted from the moon are now run at the same rate ie they both measure the same length for an hour though they may show different time (they were not synchronised when one of the clocks was on the moon.) Now, if you are correct then when we move the second clock from the moon and transport it to the space based clock the two moon clocks should show the same time. I say the clock left on the moon longer will display an earlier time than the first moon clock. How many references would you like to the correctness of this scenario??? It is my understanding that space based clocks used for GPS must have clocks that run slower in order to match Earth bound clocks. If you were right then they would need only a single correction (to compensate for the transportation to their position) and not a continual adjustment (by running slower). You've tried to explain away this phenomena before - engineers aren't listening - they just adjust the clocks and be done with it. The correction is 45,900 nanoseconds (ns) per day (not a once off correction but PER DAY). > > Or is the motional and gravitational time dilation somehow separate? > > The situation is very much more complicated than your overly simplistic > claims. The only way to actually understand this is to COMPUTE the > metric for the various situations you consider. In particular, "time > dilation" is not additive in any simple sense. It was a simple question. Thanks, you are telling me there is no simple answer. > > Please, this is not rocket science. The two forms of time dilation must > > both contribute to the total time dilation as read on a clock on the surface > > of the moon when the moon is in motion. > > It is nowhere near as simple as you think. That's a pitty. > > time dilation within > > the event horizin can not increase further because it already at maximum. [quoted text clipped - 4 lines] > observe the other clock, and the external observer cannot observe any > clock at or inside the horizon. Black Holes can evaporate, therefore clocks that were inside the event horizon can, in principle, be compared to space based clocks. > You can consider it the other way around -- consider the blueshift of > signals from an external clock to an infalling clock that falls inside [quoted text clipped - 8 lines] > measured by a single clock (+ detector); "time dilation" > cannot. Time dilation CAN be measured here on Earth and IS measured here on Earth. Red/Blue shift fits nicely into the snapshot of space/time that is modelled by GR. GR does not cope with gravitational time dilation because there is no geodesic to consider - the clocks just sit around and tick. Therefore GR is an inadequate modelling tool when it comes to considering gravitational time dilation, a phenomena *measurable here on Earth*. Indeed, you have outlined several times the inadequacy of GR in this regard which is why you prefer the red/blue shifted signals which can be modelled with the General Relativistic snapshot-of-spacetime. If I leave a clock for half an hour on the moon and then bring it back to my space clock for comparison GR is completely lost and has no way of modelling that component of time dilation acquired while the clock was stationary on the surface of the moon. > > time dilation is > > already at maximum for a stationary Black Hole. How is the additional time [quoted text clipped - 4 lines] > property of an object, it is a RELATIONSHIP between a clock and A > COORDINATE SYSTEM (not another clock). It is not helpful to think of red/blue shift when the clock being considered is frozen by all who measure it except those sharing exactly the same inertial and gravitational frame. Relative to a space observer, when one second passes on a Black Hole clock an infinite amount of time passes on a space based clock. It is simpler to just declare the black hole clock frozen. This is not something that happens only when you draw a geodesic across your spacetime diagram (so to speak). It is a permanent condition. In the life of the universe (assuming around 15 billion years) a clock in a Black Hole of the same age has yet to accumulate one second, or even one nanosecond. I don't care if you don't like it or if you can't model it in GR. It is the way it is. One could also note that a clock carried along by a beam of light that has been in transit for the entire age of the universe is also yet to accumulate a single nanosecond. It is not an intrinsic property of the clocks or the frame, but of the relative difference between two frames (as you say). In the case of the Black hole or the photon it is any other frame ie the clocks do not tick relative to any other frame including any other Black Hole or photon - not in the life of this universe. Using approximately inertial > distant coordinates in which the black hole is at rest, consider the > locus where the "time dilation" has some specific finite value (say [quoted text clipped - 12 lines] > components of the metric become important in such coordinates, and the > metric components are no longer independent of time). Considering an SR model - rods and clocks - consider a rod moving away from the observer. Assume a regular signal emitted from the rod. As the rod moves away, each successive signal has further to travel, so the signal is 'red shifted'. If the rod is massive, then gravitational time dilation (measured here on Earth as being 45,900 nanoseconds at the height of a GPS satellite as compared to a clock on the surface) means that the signal is already redshifted before it is emitted. Back to the 'light' rod, we note that the motion of the rod will cause time dilation so that the signal will be time dilated (relative to the stationary observer) at the time it is emitted. So we have additive time dilation between simple Doppler effect and relativistic time dilation (the two together give us relativistic Doppler effect) and between gravitational time dilation and simple Doppler effect. What I am asking is how the gravitational time dilation of a massive object is considered with the time dilation of a rod in motion ie a massive object in motion. You have explained that it isn't simple, but have not shown any examples of the two forms of time dilation being resolved. How red shifted would the light emitted from an Earth sized planet travelling at .9c away from an observer be relative to a near massless rod travelling at the same speed and direction? SignaturePosted by Robert Karl Stonjek >>> A clock on the moon runs slower than an equivalent space based clock. > This [quoted text clipped - 11 lines] > > Clocks on Earth run slower than space based clocks. Only when you select a specific (and common) method of defining simultaneity between here and there (i.e. choosing a coordinate system). As I said. the fact that the method you choose is simple, straightforward, and common, in no way implies you did not need to select it in order to make your claim. > You don't like the idea that clocks can accumulate asynchrony eg two clocks > placed on the moon and in one space. I NEVER said anything like that at all. I merely point out that your claims about clocks "ticking at different rates" are not independent of coordinate choice (or equivalent). Please note: what is ACTUALLY MEASURED is a difference in elapsed proper time for the two clocks, between a specified pair of events; in particular, RATES are not compared. To make a claim about their rates requires to to make ASSUMPTIONS about simultaneity between the two clocks, and such assumptions can be made is many different ways, leading to different answers. There is no question about the difference in elapsed proper times; there is great ambiguity about a putative difference in rates. <shrug> > Now, if you are correct then when we move the second clock from the moon and > transport it to the space based clock the two moon clocks should show the > same time. You clearly did not understand what I wrote. I never said or implied this at all. > Black Holes can evaporate, therefore clocks that were inside the event > horizon can, in principle, be compared to space based clocks. Hmmm. In GR, which is the only theoretical context in which black holes are well defined, they do not and cannot "evaporate". There is a rigorous theorem in GR that the area of all event horizons cannot decrease. There is a semi-classical (i.e. semi-quantum) theoretical context in which Hawking radiation can cause a black hole to evaporate after a rather enormous time. But this is not at all a complete theory, and we have no idea whether or not your claim here is valid. Indeed, it seems highly unlikely as the evaporation of a solar-mass black hole takes billions of times longer than the current age of the universe.... It could certainly be the case that by the time the black hole finally evaporates, all objects formerly inside its horizon have already been destroyed.... > Time dilation CAN be measured here on Earth and IS measured here on Earth. Sure. But not inside a black hole. <shrug> > GR does not cope with gravitational time dilation Nonsense. Indeed, GR is the only sensible way we have of discussing it. > because there is > no geodesic to consider - the clocks just sit around and tick. GR has no limitation to geodesics, and can compute elapsed proper times for clocks in any sort of motion that is allowable (i.e. timelike trajectories). > Therefore GR > is an inadequate modelling tool when it comes to considering gravitational > time dilation, a phenomena *measurable here on Earth*. Completely wrong. GR is THE ONLY way we use to model this. And the model is extremely accurate when compared to actual measurements. > Indeed, you have outlined several times the inadequacy of GR in this regard > which is why you prefer the red/blue shifted signals This is not "inadequacy of GR", it is inadequacy OF YOUR COORDINATE-DEPENDENT CLAIMS. As I have said before, by shifting to red/blueshift I can avoid coordinate dependencies and make statements about quantities that can be directly measured. You must keep track of what is (or can be) measured by what apparatus: a single clock (plus collocated detector) can measure the red/blue shift of a signal from a distant source, as long as the emitted frequency is known. That apparatus cannot measure "time dilation". Two clocks that meet, separate, and meet again can measure their elapsed proper times between meetings. That apparatus cannot measure "time dilation". To measure "time dilation" inherently requires a set of SYNCHRONIZED clocks at rest in a given coordinate system [#], and assistants pre-positioned with them along the trajectory of the clock whose "time dilation" is to be measured; the reports of the assistants must be gathered AFTER the clock passes by, and its time dilation can then be computed from their reports. A similar set-up is required to measure the tick rate of a moving clock. [#] In most cases this must be inertial to be useful. And, of course, you must CHOOSE the method of clock synchronization. NONE of your scenarios remotely resemble this latter situation. > If I leave a clock for > half an hour on the moon and then bring it back to my space clock for > comparison GR is completely lost and has no way of modelling that component > of time dilation acquired while the clock was stationary on the surface of > the moon. Again, this is completely false. Repeating falsehoods does not make them magically become true. Tom Roberts > >> What we do know is that SIGNALS from one clock to the other display a > >> difference in frequency, but there is no definitive way to assign the [quoted text clipped - 12 lines] > straightforward, and common, in no way implies you did not need to > select it in order to make your claim. The method is simple and has been oft repeated by me (again below) > > You don't like the idea that clocks can accumulate asynchrony eg two clocks > > placed on the moon and in one space. [quoted text clipped - 9 lines] > clocks, and such assumptions can be made is many different ways, leading > to different answers. No, not a pair of events (transportation of the clock to the massive body; transportation of the clock from the massive body to the space based clock) but three events - the previous two plus an interval where the clock on the massive body is left on the massive body for some length of time. If the interval representing the period of transportation of the clock is small, say 1 hour, and the interval in which the clock is on the surface is long, say one year, then it is clear that the rate at which the space based clock and the clock on the massive body run are quite different AT THE SAME TIME ie simultaneously. The establishment of simultaneity is your objection, but you seem to ignore the extended period in which the clock is stationary on the surface of the massive body. > There is no question about the difference in elapsed proper times; there > is great ambiguity about a putative difference in rates. <shrug> You have argued against the concept of clocks running slower on the surface of a massive body before. Simply placing the onus on me to frame a thought experiment in GR terms is denial of the obvious. In the scenario I outlined, the clock on the surface of the massive body MUST be running slower relative to the space based clock. If the interval in which the clock is on the massive body is very small, then simultaneity may be an issue, but if it is very large then it is clear that whilst the clock is on the massive body it must be running slower (relative to the space based clock). I am not aware of different formulation arriving at different answers except where the clock that it is transported to the surface of the massive body is immediately transported back to the space based clock and the intervals measured by the clocks compared. Where the transported clock is left on the surface of the massive body for, say, ten years, then only the standard formula for gravitational time dilation can be applied - General Relativity can not model such a thought experiment, which is a real experiment performed many times here on Earth (but if GR can, then please outline the method). > > Black Holes can evaporate, therefore clocks that were inside the event > > horizon can, in principle, be compared to space based clocks. [quoted text clipped - 12 lines] > evaporates, all objects formerly inside its horizon have already been > destroyed.... And then there is the Schwarzschild Black Hole - no need for anything to be destroyed, and matter can escape such a Black Hole eg if a large body of matter moved toward the event horizon then such a Black Hole would no longer have sufficient mass to be a Black Hole and the matter could escape, say in a low density Schwarzschild Radius of around the size of our visible universe. Destroying real clocks has never prevented them being sent to near the speed of light or into hot suns or whatever, so I don't think that is a valid argument with respect to thought experiments. Einstein's clocks would have been destroyed many times over, but that certainly did not prevent him. > > Time dilation CAN be measured here on Earth and IS measured here on Earth. > > Sure. But not inside a black hole. <shrug> Time dilation increases with the mass of the massive object. Using this formula, simple gravitational time dilation, we find that a clock should stop in a Black Hole, whether that BH is formed by a collapsing star and has a singularity at its centre or whether the BH is a Schwarzschild radius and contains galaxies that in turn contain habitable planets. > > GR does not cope with gravitational time dilation > > Nonsense. Indeed, GR is the only sensible way we have of discussing it. What is the GR formulation for calculating the difference in rate of a clock on the surface of the Earth compared to one at the height of GPS satellite? Note that the Earth based atomic clocks are never transported into space. How would you establish simultaneity for such a calculation? > > because there is > > no geodesic to consider - the clocks just sit around and tick. > > GR has no limitation to geodesics, and can compute elapsed proper times > for clocks in any sort of motion that is allowable (i.e. timelike > trajectories). A clock on the surface of a planet is not in motion relative to the space based clock with which we are making our comparisons. No motion, no GR? To establish the asynchrony between clocks let each clock emit a signal at 1s intervals. The space based clock observer will note that the signals arriving from the Earth bound clock are received at intervals of less than 1s and the Earth based observer will note that the signal from the space based clock arrive at less than 1s intervals. > > Indeed, you have outlined several times the inadequacy of GR in this regard > > which is why you prefer the red/blue shifted signals [quoted text clipped - 3 lines] > red/blueshift I can avoid coordinate dependencies and make statements > about quantities that can be directly measured. Red/blueshift of a signal beamed from Earth to a space observer or visa versa does not tell one which component of the signal is responsible for the frequency shift ie it could be the curvature of space between emitter and absorber or the slower/quicker clock at the emitter or the absorber. To measure gravitational time dilation we need to measure only the rate of the clock at the surface and not the red/blueshift caused by curvature of space between the emitter and absorber. This can be done by emitting a pulse train from the Earth bound clock. As long as the space observer is not moving relative to the Earth bound clock then the interval between pulses is all that is needed to determine the time dilation - the curvature of space between the two is irrelevant unless the curvature is so great that signals are never received. Simultaneity is not a required component of such measurement. The clocks do not have to be synchronised - they only need to be of the same type. How does GR do with such simple scenarios. > You must keep track of what is (or can be) measured by what apparatus: a > single clock (plus collocated detector) can measure the red/blue shift [quoted text clipped - 10 lines] > computed from their reports. A similar set-up is required to measure the > tick rate of a moving clock. All you are saying is that time dilation can not be measured by a single measurement, that two or more measurements must be taken. So what? Why is this a constraint of any kind? Time, by its very nature, is a multiple measurement (of ticks or atomic decay or whatever). That does not make the phenomena any less valid. You seem to be implying that time dilation should be ignored because it can't be measured with a single measurement. You are advocating the measurement of red/blueshift, but red/blueshift does not report time dilation - the two may be quite separate as when a signal is red shifted as it passes from a massive body to a space observer. But the clock on the surface of a massive body is slower than a space clock whether a signal is sent or not. As you say, this requires more than one measurement. Why should that be any problem at all? In SR, it is par for the course. In GR, which is geared toward modelling single events, there is no neat way to measure time dilation, even with multiple measurements. This is a shortcoming - don't blame me. > [#] In most cases this must be inertial to be useful. And, of > course, you must CHOOSE the method of clock synchronization. > > NONE of your scenarios remotely resemble this latter situation. You can measure time dilation without synchronising clocks. You only need to know the interval between events in two places eg if a signal is sent from the planet to the space observer every hour. Even if there is red/blueshift of that signal, the same red/blue shift should occur each time so the interval should be the same if the clocks are not time dilated. But if the planet based clock is time dilated then the signals will be further apart than one hour. The amount of the difference between clocks increases as the interval increases eg one minute, one hour, one year, ten years. If the space curvature is the cause of the apparent time dilation then it should be the same regardless of the interval between signals. QED (achieved *without* synchronising clocks). > > If I leave a clock for > > half an hour on the moon and then bring it back to my space clock for [quoted text clipped - 4 lines] > Again, this is completely false. Repeating falsehoods does not make them > magically become true. Not bothering to point out how it would be modelled in GR (in principle or general outline) does nothing to prove your point. The best you've managed to do thus far is to point out how wonderfully accurate GR can model red/blueshift. But such frequency shift does not indicate time dilation. The fact that multiple measurements need to be taken only establishes the relevance of time dilation and the fact that it is a separate phenomena ie one that can not be measured in a single instant, such as the measurement of red/blueshift. Therefore, by your own logic, red/blueshift does not indicate time dilation because, as you say, time dilation can only be measured using multiple measurements. Therefore measurement of red/blueshift is no substitute for measurement of time dilation, which is the subject of my inquiry (not red/blueshift). SignatureKind Regards Robert Karl Stonjek Lost of their energy would limit their speed... -- Ahmed Ouahi, Architect Best Regards! > > >> What we do know is that SIGNALS from one clock to the other display a > > >> difference in frequency, but there is no definitive way to assign the [quoted text clipped - 237 lines] > Kind Regards > Robert Karl Stonjek > Using this addition logic we come to Black Holes where time dilation is > already off the scale (or gamma etc etc - I am just using time dilation > as an example of relativistic changes). Thus a black hole can not be > accelerated - it can not move from its current spatial location - it > stays put. Said in another way - regardless of the mass of a black > hole, it would take an infinite amount of energy to move it nowhere. Only if you were IN The black hole. The MASS of the black hole is NOT infinite. Picture a 1 gram black hole, radius 1.4x10^-30 meters (kinda small, it would be 5.2x10^-16 of the 'classical radius' of an electron.) Anyway, if you put enough of an electric charge on this very small black hole, you could 'suspend it' in an electric field, move it around as you liked, etc., just as you could do with any one gram mass. <http://ocw.mit.edu/NR/rdonlyres/Physics/8-02TSpring-2005/4740D0A6-7089-4B1F- B048-067E57905AFE/0/summary_w03d1.pdf> http://tinyurl.com/24ap3c It would take no more energy to move it than it would to move any other 1 gm mass. > In other words a Black Hole can not acquire relativistic time dilation > caused by its relative motion. Thus all observers must be moving > relative to the local Black Hole. Afraid that your 'local absolute reference' to a black hole has evaporated. The micro black hole aside, if there is a black hole at the center of our galaxy (and there are good reasons to believe there is), that black hole is in motion with respect to black holes that are located in other galaxies. Gravity is accelerating the black holes. (this invalidates your thesis) Both gravity, magnetic fields AND electric fields (among other things) can and do seem to 'escape' a black hole. Therefore, the black hole IS influenced by its surroundings and influences them. http://en.wikipedia.org/wiki/Black_hole > Obviously I have saved ink by framing conjecture and intuitive reasoning > in a "this is so" format ie I have omitted the apologies for thinking > until here. Please read the above as a set of questions rather than > proposed answers. Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap What would happen if you eat a mini black hole ? > > Using this addition logic we come to Black Holes where time dilation is > > already off the scale (or gamma etc etc - I am just using time dilation [quoted text clipped - 12 lines] > hole, you could 'suspend it' in an electric field, move it around as you > liked, etc., just as you could do with any one gram mass. <http://ocw.mit.edu/NR/rdonlyres/Physics/8-02TSpring-2005/4740D0A6-7089-4B1F - > B048-067E57905AFE/0/summary_w03d1.pdf> > http://tinyurl.com/24ap3c [quoted text clipped - 31 lines] > > bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap "josefmatz" <josefmatz@arcor.de> wrote in news:45f562a1$0$23143$9b4e6d93 @newsspool1.arcor-online.net: > What would happen if you eat a mini black hole ? It would be a boring experience. You would get a maxi stomach ache. The black hole would bore a hole through you as it fell toward the center of the earth. The tidal forces it exerted would be small, to begin with, but enough to kill cells near its path. (and probably you) Each time it got too close to a particle it would 'eat it', giving off some rather nasty radiation in the process. I doubt that you would relish the experience, or survive it. It would then oscillate back and forth through the earth as it ate the earth. Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap > > Using this addition logic we come to Black Holes where time dilation is > > already off the scale (or gamma etc etc - I am just using time dilation [quoted text clipped - 5 lines] > Only if you were IN The black hole. > The MASS of the black hole is NOT infinite. I never did say that the mass was infinite. However, time dilation within the event horizin can not increase further because it already at maximum. Not that the inertia of an object at high speed increases to infinite even though its rest mass remains the same. > Picture a 1 gram black hole, radius 1.4x10^-30 meters (kinda small, > it would be 5.2x10^-16 of the 'classical radius' of an electron.) > > Anyway, if you put enough of an electric charge on this very small black > hole, you could 'suspend it' in an electric field, move it around as you > liked, etc., just as you could do with any one gram mass. <http://ocw.mit.edu/NR/rdonlyres/Physics/8-02TSpring-2005/4740D0A6-7089-4B1F - > B048-067E57905AFE/0/summary_w03d1.pdf> > http://tinyurl.com/24ap3c > > It would take no more energy to move it than it would to move any other 1 gm > mass. That would be the intuitive first approximation. However, time dilation is already at maximum for a stationary Black Hole. How is the additional time dilation caused by the motion of the Black Hole summed to its intrinsic time dilation? Does time run backward? For light speed, where time dilation is also at maximum, the speed can not be increased by emitting light from a moving body. A similar phenomena may apply to Black Holes, but with the apparent motion being the illusion. > > In other words a Black Hole can not acquire relativistic time dilation > > caused by its relative motion. Thus all observers must be moving [quoted text clipped - 6 lines] > in motion with respect to black holes that are located in other galaxies. > Gravity is accelerating the black holes. (this invalidates your thesis) I am asking how the additional time dilation caused by an accelerating object is resolved within the Black Hole. I offered one solution. Distal motion may be an illusion. How, for instance, are you going to determine which of two Black Holes is moving? As you approach a Black Hole, everything you can measure indicates that it is unmoveable and so must be stationary. This illusion is already known for light. The speed of light is c as measured from any inertial frame. I am saying that a complementary phenomena is that of the Black hole - that the speed of a Black Hole is zero as measured from any inertial frame. We might ask "but all light can not have the same speed!!" That is the classical (Newtonian) conclusion. Why do we assume that the same classical three dimensional space model will apply to Black Holes? Robert >> > Using this addition logic we come to Black Holes where time dilation >> > is already off the scale (or gamma etc etc - I am just using time [quoted text clipped - 8 lines] > > I never did say that the mass was infinite. That is implied when you say that a black hole can not be accelerated. When you say it can not move from its current spacial location, you also imply some 'absolute' set of coordinates. Picture a body that is ready to become a black hole, as soon as another gram of matter is added. This body is moving at .5 c wrt the earth. We add 1 gram of matter and the body collapses into a black hole. By your logic, it must suddenly stop moving, like a car that has dropped its motor. Oh, but you say that the car doesn't stop moving instantly because it has inertia. So too with the black hole. > However, time dilation > within the event horizin can not increase further because it already at > maximum. > > Not that the inertia of an object at high speed increases to infinite > even though its rest mass remains the same. I think you are lost in contemplation of singularities and their properties. >> Picture a 1 gram black hole, radius 1.4x10^-30 meters (kinda small, >> it would be 5.2x10^-16 of the 'classical radius' of an electron.) [quoted text clipped - 20 lines] > increased by emitting light from a moving body. A similar phenomena may > apply to Black Holes, but with the apparent motion being the illusion. We can only look from one side at any Schwarzschild radius. We have to look from the outside or from the inside, not both. >> > In other words a Black Hole can not acquire relativistic time >> > dilation caused by its relative motion. Thus all observers must be [quoted text clipped - 13 lines] > I am asking how the additional time dilation caused by an accelerating > object is resolved within the Black Hole. I offered one solution. It does not matter to those OUTSIDE the black hole. From the outside, it should (and apparently does) act much like any other mass. As for 'from the inside', there are indications that our universe is a black hole (as seen from the outside), so you KNOW what things are like inside a black hole. What happens crossing the event horizon? That is something that we can never know unless we cross an event horizon, and then we can not report back our findings to those on the other side. > Distal motion may be an illusion. How, for instance, are you going to > determine which of two Black Holes is moving? Just as you do for anything else in the universe, you compare with other things. > As you approach a Black > Hole, everything you can measure indicates that it is unmoveable This is as true for a black hole as for any other massive body; which means that it is false. > and so > must be stationary. and that is poor logic. > This illusion is already known for light. The speed of light is c as > measured from any inertial frame. I am saying that a complementary > phenomena is that of the Black hole - that the speed of a Black Hole is > zero as measured from any inertial frame. And you are incorrect. Imagine an inertial frame tied to the center of our galaxy, which probably contains a giant black hole. Imagine another inertial frame tied to the center of another galaxy (pick one, almost any one as most seem to contain black holes). By your logic, neither of those inertial frames can move with respect to the other. But galaxies are in relative motion with respect to each other. There seems to be a contradiction somewhere. Perhaps your assumptions are wrong. Perhaps one CAN measure the motion of a black hole as long as one is outside of the black hole. > We might ask "but all light can not have the same speed!!" That is the > classical (Newtonian) conclusion. Why do we assume that the same > classical three dimensional space model will apply to Black Holes? The classsical three dimensional space model will not apply as we cross the boundry (Schwarzschild radius) between outside and inside, but certain laws of physics still apply. Gravity must cross the boundry, otherwise the black hole would completely disappear as soon as it came into existance. Inertia must because it is tied to gravity. Once you have the 'handles' of gravity and inertia, to use to contact the black hole, it must obey the same laws of physics, with respect to those properties as must any other mass. Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap > >> Only if you were IN The black hole. > >> The MASS of the black hole is NOT infinite. [quoted text clipped - 15 lines] > > So too with the black hole. You can't simply add a bit of matter to an object to form a Black Hole. You are forgetting General Relativity. Think of the rubber sheet model. When an object moves, it is like a steel ball rolling across the sheet - the sheet deforms. Consider a bowling ball sitting in the middle of the sheet. Now a small ball rolls past it, deforming the sheet as it goes. As it passes the bowling ball, the sheet around the larger ball is ever so slightly lowered on the side of the smaller ball and the bowling ball moves toward it. In principle, in a darkish corner of the universe, a sun sized (dark) object will move slightly toward a single passing photon. Now we take the Black Hole. It deforms the sheet so much that it does not move when a photon passes by. This is because the sides of the rubber sheet are perfectly vertical. So when an object passes by the ball representing the Black Hole it might go down a little lower in the sheet, but it does not move in the direction of the massive object passing by - not one millimetre, even if the other object was also a black hole. The steepness of the sheet, or of spacetime near a Black Hole, is often given as an analogue of GR. Here is a more classical reason to consider the stationary status of the Black Hole. As time dilation is infinite on the Surface (or equivalent for Black Holes) of the Black Hole is infinite/zero (infinite interval between events, frequency of events is zero relative to any clock not in the same inertial frame) it takes an infinite amount of time for the Black Hole to move toward a passing massive object. As for absolute spatial coordinates - a lack of absolute spatial coordinates never stopped a photon from passing an observer at the speed of light. The same argument can be made for the Black Hole. The black hole is not stationary relative to some absolute spatial coordinate, but is stationary relative to whatever frame you care to measure it from (just as the speed of light is c as measured from any inertial frame). As for acceleration we only need to think of the rubber sheet model once more and the way the sheet deforms when an object accelerates. For a Black Hole the sides of the sheet are vertical and can not deform into a shape typical of an accelerating object ie a little steeper at the front, a little shallower at the rear (in SR, clocks on an accelerating rod will slow at different rates with the clock on the leading edge running slower than the clock on the trailing edge). Thus a Black Hole is stationary with respect to all inertial frames and a Black Hole can not accelerate. But Black Holes are not stationary with respect to some absolute spatial coordinate just as photons do not travel at c with respect to some absolute stationary frame. The speed that two Black Holes may have relative to each other is similar in nature to the 2*c one may measure for the speed difference of two photons travelling in opposite directions. Consider two objects travelling at fractionally lower than c and in the opposite direction - measured from either object the other object is travelling at less than c with respect to it. > >> in motion with respect to black holes that are located in other > >> galaxies. Gravity is accelerating the black holes. (this invalidates [quoted text clipped - 9 lines] > black hole (as seen from the outside), so you KNOW what things are like > inside a black hole. That is a Schwarzschild radius, not a singularity. But you raise an interesting point. If the universe were infinite then at any point in the universe you would be on the event horizon of a Schwarzschild radius. Consider any direction you like (pretending, for a moment, that our universe is infinite). The matter in the direction you are looking will form a Schwarzschild Black Hole with a centre at distance r=(3c^2/8Gdpi)^.5 Thus the more dense the matter in that direction the shorter the distance to the centre (of the BH). But this is going to be true in any direction you care to look - you'll see a Schwarzschild Back Hole. Now consider what you see from the event horizon of a low density Schwarzschild Black Hole when you look from the event horizon toward the centre. We know that time dilation increases as you get closer to the black hole centre. So light will be progressively more redshifted. Now, in an infinite universe there is a Schwarzschild radius in whatever direction you look so light will be red shifted with greater distance in any direction you care to look. Say, isn't that EXACTLY what we see in our universe? Must be a coincidence? Note that a General Relativistic modelling of the above would show that space is expanding in any direction you look (just as space expands as you look from the event horizon toward the centre of a Black Hole of any kind). Say, isn't that EXACTLY what we see in our universe? Must be a coincidence? SignatureKind Regards Robert Karl Stonjek > BZ said: (attribution added, to fix your trimming out of attributions. Quoting without attribution is a 'usenet no-no'.) >> >> Only if you were IN The black hole. >> >> The MASS of the black hole is NOT infinite. [quoted text clipped - 17 lines] > > You can't simply add a bit of matter to an object to form a Black Hole. Who says? Take one neutron cold neutron star, lacking only one gram of mass of having enough mass to be a black hole. Drop a gram on it. Neutrons collapse. Black hole forms. > You are forgetting General Relativity. Think of the rubber sheet model. > When an object moves, it is like a steel ball rolling across the sheet - > the sheet deforms. ok. (remember that the rubber sheet model is only a very limited picture of the math.) > Consider a bowling ball sitting in the middle of the sheet. Now a small > ball rolls past it, deforming the sheet as it goes. As it passes the > bowling ball, the sheet around the larger ball is ever so slightly > lowered on the side of the smaller ball and the bowling ball moves > toward it. Yep. > In principle, in a darkish corner of the universe, a sun > sized (dark) object will move slightly toward a single passing photon. Photons do not have rest mass. There is no evidence that their inertial mass will attract massive bodies during the brief 'near contact' that takes place as they pass nearby. > Now we take the Black Hole. It deforms the sheet so much that it does > not move when a photon passes by. Take a black hole that is rolling across the sheet, in an orbit with a neutron star that is 2 Au away from it. > This is because the sides of the > rubber sheet are perfectly vertical. Incorrect. The sides approach 'vertical' as they approach the Schwarzchild radius. They are only 'vertical' at that radius. What happens inside that radius is unknowable to those on the outside. Neither mass, inertia, charge, nor angular momentum are lost when an object becomes a black hole. > So when an object passes by the > ball representing the Black Hole it might go down a little lower in the > sheet, but it does not move in the direction of the massive object > passing by - not one millimetre, even if the other object was also a > black hole. Your model is broken. > The steepness of the sheet, or of spacetime near a Black Hole, is often > given as an analogue of GR. Here is a more classical reason to consider [quoted text clipped - 4 lines] > infinite amount of time for the Black Hole to move toward a passing > massive object. Demonstrably incorrect. The black hole at the center of our galaxy did NOT stop its motion when it formed. > As for absolute spatial coordinates - a lack of absolute spatial > coordinates never stopped a photon from passing an observer at the speed > of light. Correct. > The same argument can be made for the Black Hole. If you do, you proceed contrary to evidence. > The black > hole is not stationary relative to some absolute spatial coordinate, but > is stationary relative to whatever frame you care to measure it from > (just as the speed of light is c as measured from any inertial frame). Stop and think. That means that nothing can ever approach a black hole. I can not move toward something that has zero relative velocity with respect to me. If I take a step in its direction, it MUST 'take a step away from me' because it MUST maintain zero relative velocity WRT me at all times. Do you see why your concept is not tenable? > As for acceleration we only need to think of the rubber sheet model once > more and the way the sheet deforms when an object accelerates. For a [quoted text clipped - 14 lines] > measured from either object the other object is travelling at less than > c with respect to it. Your arguments are inconsistent with your suppositions. >> >> in motion with respect to black holes that are located in other >> >> galaxies. Gravity is accelerating the black holes. (this invalidates [quoted text clipped - 12 lines] > > That is a Schwarzschild radius, not a singularity. Correct. I did not say it was a singularity. > But you raise an interesting point. If the universe were infinite then > at any point in the universe you would be on the event horizon of a [quoted text clipped - 15 lines] > any direction you care to look. Say, isn't that EXACTLY what we see in > our universe? Must be a coincidence? Maybe not. > Note that a General Relativistic modelling of the above would show that > space is expanding in any direction you look (just as space expands as > you look from the event horizon toward the centre of a Black Hole of any > kind). Say, isn't that EXACTLY what we see in our universe? Must be a > coincidence? Perhaps 'expanding in any direction' is the result of 'center of the black hole is in any direction'. It doesn't much matter as the 'black hole we are at the center of' is the light radius of the visable universe that we see. Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap > > Now we take the Black Hole. It deforms the sheet so much that it does > > not move when a photon passes by. [quoted text clipped - 8 lines] > radius. They are only 'vertical' at that radius. What happens inside that > radius is unknowable to those on the outside. So the sides could be vertical. Note that light can not escape etc. > Neither mass, inertia, charge, nor angular momentum are lost when an object > becomes a black hole. [quoted text clipped - 6 lines] > > Your model is broken. Why? > > The steepness of the sheet, or of spacetime near a Black Hole, is often > > given as an analogue of GR. Here is a more classical reason to consider [quoted text clipped - 7 lines] > Demonstrably incorrect. The black hole at the center of our galaxy did NOT > stop its motion when it formed. Stop with respect to what? Inertial motion is a relative quantity, not an absolute. If an object deforms space as much as a Black Hole does then everything else is in motion relative to it just as light is at c relative to any inertial frame. Note that the object that emits light is not stationary with respect to the photon as judged by some other frame even though the light emitted darts off at c. As there is no absolute frame, then there can be more than one stationary point relative to other frames just as there can be more than one direction of the speed of light relative to other frames. Now we say that the speed of light is c from any frame, but we also note that two photons can be moving in opposite directions which gives us a total of 2*c. Well, if we do the math for two objects near the speed of light moving in opposite directions we find that the speeds don't add up trivially and that the speed of one object as measured from the other is never more than c, and so, by extension, we can speculate that even from a photon frame we would never measure the speed of a photon travelling in the opposite direction as greater than c. Now we consider the Black Hole. From a near Black Hole (just requiring that teaspoon full of matter you mentioned earlier) every bit of matter in space as viewed from this frame appears to be moving at just below the speed of light. As the object (say, a neutron star) is spherical, we can observe moving objects in any direction. We note that the direction of the fast moving space objects rules out all but a tiny motion for the neutron star. That is because there is no way that any of the observed objects could be stationary with respect to the neutron star. This apparent motion is caused by the time dilation of the observer on the Neutron star. Note that due to the mass of the neutron star there will be a lot of matter heading straight for it. How can you count yourself moving with respect to all of that infalling matter? The greater the time dilation of the surface observer the greater the speed and volume of the infalling matter. For the Black Hole, (a Schwarzschild variety, where habitable planets can survive :) the infall would be at the speed of light. If you were in the centre of such a Schwarzschild radius you would note the speed of objects to be moving toward you at ever greater speed with distance, like the observed red shift of our universe but in reverse. > > As for absolute spatial coordinates - a lack of absolute spatial > > coordinates never stopped a photon from passing an observer at the speed [quoted text clipped - 5 lines] > > If you do, you proceed contrary to evidence. 'Stationary' is a relative thing. One may note that two Black Holes may be moving with respect to each other in the same way that two photons appear to be moving away from each other at 2c. But we know that nothing moves at greater than c relative to any inertial frame. Note that if you get close enough to a Black Hole you will find that you are moving at the speed of light relative to it and any other Black Hole you can see. Yes, Black holes seem to be moving relative to each other. Yes, a photon may appear to be travelling at up to 2*c relative to another photon. > > The black > > hole is not stationary relative to some absolute spatial coordinate, but > > is stationary relative to whatever frame you care to measure it from > > (just as the speed of light is c as measured from any inertial frame). > > Stop and think. That means that nothing can ever approach a black hole. Huh?? It means that *everything* is moving relative to a Black hole!!! Nothing can approach the speed of light. The Black Hole phenomena is opposite - nothing can escape it. If you measure something as stationary then it means that you must be moving. I did not say that a Black Hole shares everyone else's frame - quite the opposite. > I can not move toward something that has zero relative velocity with > respect to me. If I take a step in its direction, it MUST 'take a step away > from me' because it MUST maintain zero relative velocity WRT me at all > times. > > Do you see why your concept is not tenable? Sorry, I obviously didn't make myself clear previously. When there is a differential speed between two frames, yours and someone else's, you can always count yourself as stationary and the other as moving and do all your relativistic calculations from that perspective. Or you could choose to count the other frame as stationary and yours as the moving frame (so your clocks are running slower rather than their clocks). We do not have this freedom when considering a photon - we can not count the photon as stationary and our frame as the one moving at the speed of light. For all other motion we do have that freedom. Now, what I am saying is that there is another limitation - the Black Hole. Sure we can count our frame as the one that is moving and the Black Hole as stationary, but what I am saying is that we do not have the freedom to assume the reverse ie that the Black Hole is moving and that we are stationary with respect to it. The same is true from any third person observer - the Black Hole must always be the stationary frame relative to the other frame observer. We do the same with the speed of light - the speed of light is always in motion and the other frame relatively stationary with respect to it. > > But you raise an interesting point. If the universe were infinite then > > at any point in the universe you would be on the event horizon of a [quoted text clipped - 27 lines] > hole is in any direction'. It doesn't much matter as the 'black hole we are > at the center of' is the light radius of the visable universe that we see. I think you'll find that we are not at the centre of a Black Hole. Rather, we are at the event horizon of a Black Hole in any direction. In an infinite universe the bulk of matter is going to be away from the observer in any direction. In a finite universe you are within the bulk of matter. Thus in an infinite universe an inverted Schwarzschild radius forms. From the centre of a regular low density Schwarzschild radius you would note an increased blue shift with distance and matter would appear to be approaching one (infilling) at ever greater speed with distance. But if the bulk of the mass is far away, as with an infinite universe, the Schwarzschild radius is effectively inverted so that the event horizon becomes a point and the centre becomes a shell. That's slightly weird, but nothing as weird as "the universe was the size of a pea after starting from a quantum fluctuation and then, for no reason, inflated etc" or "And on the seventh day he rested". SignatureKind Regards Robert Karl Stonjek > Sorry, I obviously didn't make myself clear previously. When there is a > differential speed between two frames, yours and someone else's, you can [quoted text clipped - 4 lines] > > We do not have this freedom when considering a photon That is because an inertial frame can not be based upon anything moving at c. This is ruled out because composition of any velocity with c yealds c. > - we can not count > the photon as stationary and our frame as the one moving at the speed of > light. For all other motion we do have that freedom For all inertial mostions of less than c we have that freedom. > Now, what I am saying is that there is another limitation - the Black > Hole. Sure we can count our frame as the one that is moving and the > Black Hole as stationary, Not really. You can position an inertial frame at the same location as the black hole's center of mass, but you can not base an inertial frame upon a non inertial item and a black hole is non inertial. (acceleration [gravity]is involved]) > but what I am saying is that we do not have > the freedom to assume the reverse ie that the Black Hole is moving and > that we are stationary with respect to it. On the contrary, we can have a black hole move within our inertial FoR but we can not move within its inertial FoR because it does not have one. > The same is true from any third person observer - the Black Hole must > always be the stationary frame relative to the other frame observer. We > do the same with the speed of light - the speed of light is always in > motion and the other frame relatively stationary with respect to it. That supposition loses your earlier assertion that the black hole represented an object with zero motion wrt the univers around it AND is logically unsupportable. Let us suppose that we consider the black holes [nonexistant] iFoR to be congruent with that FoR based upon the black holes center of gravity. Let us consider any other iFoR that is in motion wrt the BHiFoR. You will have to show that ANY such iFoR can not exist in order to support your original supposition. But there is no reason to suppose that any iFoR has special properties (in the absence of a BH). How does centering an iFoR upon the center of a BH suddenly invalidiate ALL other iFoR's in the universe? Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap On Mar 13, 1:05 am, "Robert Karl Stonjek" <ston...@ozemail.com.au> wrote: > > > Using this addition logic we come to Black Holes where time dilation is > > > already off the scale (or gamma etc etc - I am just using time dilation [quoted text clipped - 52 lines] > I am asking how the additional time dilation caused by an accelerating > object is resolved within the Black Hole. I offered one solution. ...whose time compared to whose time? How are you doing the comparing? > Distal motion may be an illusion. How, for instance, are you going to > determine which of two Black Holes is moving? As you approach a Black Hole, > everything you can measure indicates that it is unmoveable and so must be > stationary. Lense-Thrilling effect or the Shapiro effect to determine angular velocity, and simply watching to determine translational velocity - follow the blur. > This illusion is already known for light. The speed of light is c as > measured from any inertial frame. I am saying that a complementary > phenomena is that of the Black hole - that the speed of a Black Hole is zero > as measured from any inertial frame. That is silly and has no justification whatsoever. > We might ask "but all light can not have the same speed!!" That is the > classical (Newtonian) conclusion. Why do we assume that the same classical > three dimensional space model will apply to Black Holes? It doesn't, and we don't. > Robert > > > The micro black hole aside, if there is a black hole at the center of our > > > galaxy (and there are good reasons to believe there is), that black hole [quoted text clipped - 6 lines] > > ...whose time compared to whose time? How are you doing the comparing? A space observer compared to a clock on the surface of the Black Hole. A black hole can evaporate, so relative time recorded on the two clocks can be compared (in principle). One does not have to transport the clock from the surface into space. I define the surface as the surface of a neutron star that collapses to form a black hole. Just exactly where the clock ends up I do not know. > > Distal motion may be an illusion. How, for instance, are you going to > > determine which of two Black Holes is moving? As you approach a Black Hole, [quoted text clipped - 4 lines] > velocity, and simply watching to determine translational velocity - > follow the blur. Who is moving - the observer or the Black Hole?? In the case of a passing beam of light we always know it is the beam of light that is moving because light speed is not possible for massive bodies. But apart from light, either the observer or the object observed could be moving, but no-one can pronounce from on high, having seen the answer in some burning bush, that one or the other is necessarily stationary with respect to the other. The only caveat to my re-jigging of the common-or-garden variety of the twins paradox is where one object accelerates (say object B), say one object turns around and heads in the opposite direction. We can still not say whether object B was stationary before it turned or after it turned or neither before or after (eg only object A is stationary with respect to B and B is never stationary with respect to object A). If it is possible for a black hole to have inertial motion, which seems reasonably plausible, acceleration is something else. When an object accelerates the time dilation on one part of the object, say the leading edge, does not necessarily match the other, say the trailing edge. If you were to push a black hole, would the event horizon deform and how would this be modelled? It is not as simple as one might think. > > This illusion is already known for light. The speed of light is c as > > measured from any inertial frame. I am saying that a complementary > > phenomena is that of the Black hole - that the speed of a Black Hole is zero > > as measured from any inertial frame. > > That is silly and has no justification whatsoever. True, but light is c regardless of the inertial frame from which it is measured. I know this seems silly and counter-intuitive but it has been confirmed numerous times and is now accepted as fact. When the time dilation of an object falls to zero/infinite (frequency of events falls to zero, infinite interval between events), weird things happen. > > We might ask "but all light can not have the same speed!!" That is the > > classical (Newtonian) conclusion. Why do we assume that the same classical > > three dimensional space model will apply to Black Holes? > > It doesn't, and we don't. You have a reference for that? Or do you just believe that speed of light weirdness can be ignored if we don't look too carefully? SignatureKind Regards Robert Karl Stonjek "Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in news:15sKh.11857 $8U4.7386@news-server.bigpond.net.au: > If you were to push a black hole, would the event horizon deform and how > would this be modelled? It is not as simple as one might think. You can't push a rope, you have to pull it. Pushing implies a physical contact which would be rather dangerous. There are not many ways to 'push' a black hole that I can imagine. The only push I can think of is 'like charges repel'. So you would need to pump a lot of electrons (or positrons) into the black hole and then bring a similarly charged large (low mass) electrode near. Charged body interactions, as with mass interactions are most simply modeled as point objects containing all the mass or charge. I see no reason to suppose the event horizon would deform. I have no idea how to model this, do you? By the way, when you quote an article in order to reply to it, if you cut all the 'citations and credits' no one can tell to whom you are talking nor who said what. You should retain the citations for all quoted material that you retain in your posting. Signaturebz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap > "Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in news:15sKh.11857 > $8U4.7386@news-server.bigpond.net.au: [quoted text clipped - 21 lines] > who said what. You should retain the citations for all quoted material that > you retain in your posting. Messages can get awfully long. The reply is contextual ie the next one in the thread. Others can always look back to the previous message. But for short ones like this message there is no problem in keeping it all :) Yes, the only way I can think of moving a Black Hole is to poke a massive object in front of it (relative to the direction you want the Black Hole to move) and hope that it will follow. I don't think this would happen. I think the Black Hole would stay put. Let's consider the quantum angle - any boson of gravity would have to move at greater than the speed of light to communicate force between the two objects. Thus I don't think you can accelerate a Black Hole. Whilst you may consider the Black Hole to be moving, when you get up close it will appear to be stationary. The phenomena must be similar to that of light. Whilst I measure the speed of light to be c, by accelerating to 0.99c I find that light is still darting off at c!! As you get close to a Black Hole, everything seems to be moving at close to the speed of light relative to the Black Hole (including the observer - you just can't slow down!!). Thus you would have to conclude that it is the Black Hole that is most likely to be stationary with respect to these rapidly moving objects. The other thing to consider is the collision of a star size object with a Black Hole. One would think that the momentum of the star would knock the Black Hole along. But all infalling matter reaches the speed of light, so the momentum that the star had before it reaches the event horizon counts for nothing. Indeed, I would speculate that excess momentum that any object has as it falls toward the event horizon is radiated off as energy. SignatureKind Regards Robert Karl Stonjek >> "Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in >> news:15sKh.11857 $8U4.7386@news-server.bigpond.net.au: [quoted text clipped - 31 lines] > But for short ones like this message there is no problem in keeping it > all :) This reasoning is bad for the following reason: a person later seeing your article quoted has no way of knowing who said what. They may incorrectly attribute something that someone else said to you. Or something you said to someone else. Sloppy attribution would lead to major problems later. There is really no excuse for it. > Yes, the only way I can think of moving a Black Hole is to poke a > massive object in front of it (relative to the direction you want the > Black Hole to move) and hope that it will follow. I don't think this > would happen. I think the Black Hole would stay put. I think most who study black holes would disagree with you. > Let's consider the quantum angle - any boson of gravity would have to > move at greater than the speed of light to communicate force between the > two objects. What you are saying, were it true, would tend to invalidate the idea that a 'boson of gravity' is contratined to c AND that the 'boson of gravity' is the mechanism by which gravity works. > Thus I don't think you can accelerate a Black Hole. Whilst you may > consider the Black Hole to be moving, when you get up close it will > appear to be stationary. If the car in front of me on the expressway drops its motor, it suddenly stops moving AND I crash into it. You want it to stop moving with respect to me, which means it MUST keep moving, but match my velocity. It must also match the velocity of the police car that is coming up behind me at 80 mph (I am doing 60 and the car ahead of me must be doing 60 with respect to MY surroundings but must be doing 80 wrt the surroundings of the police car. The problem with that is that the surroundings of my car and of the police car are the same. They can NOT be moving at 60 and at 80. You theory is falsified. > The phenomena must be similar to that of > light. Why? because your intuition tells you so? > Whilst I measure the speed of light to be c, by accelerating to > 0.99c I find that light is still darting off at c!! Yep. > As you get close to > a Black Hole, everything seems to be moving at close to the speed of > light relative to the Black Hole (including the observer [but the observer is NOT moving at nearly c in HIS FoR] > - you just > can't slow down!! On the contrary, The observer CAN slow down, but he can never stop completely. > ). Thus you would have to conclude that it is the > Black Hole |
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