Naked Science Forum
On the Lighter Side => New Theories => Topic started by: MikeS on 20/03/2012 06:40:40
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I wrote this in a mainline thread and was told to move it to new theories.
http://www.thenakedscientists.com/forum/index.php?topic=43374.0
"An object with a large mass is travelling from dilated time to a less dilated time and it does that continuously. This is acceleration."
Let's take that statement apart to see where the various ideas it expresses came from.
1) An object with a large mass dilates 'local' time relative to a distant observer.
2)Therefore, time is more dilated closer to the object than further away, again as perceived by a distant observer.
3) All objects are travelling through space-time continuously.
Therefore
"An object with a large mass is travelling from dilated time to a less dilated time and it does that continuously."
That is in full accord with GR.
4) In physics, acceleration is the rate of change of velocity with time.
However, it can equally be a constant (or changing) velocity with a changing rate of time (changing time dilation factor.)
5) Therefore an object in an environment where time is contracting is accelerating.
Any massive object creates it's own gravitationally warped space time in which it is continually accelerating as it is continuously travelling through space time from a 'place' where' time is passing slower to a place where time is passing faster (relative to a distant observer).
Any object, feather or cannon ball, in free fall accelerates towards the Earth with a constant acceleration. They 'fall' at the same rate. This is very non-intuitive.
It is equally valid to consider the Earth as accelerating toward the object.
Looked at from that perspective it explains in an intuitive way why all objects 'fall' at the same rate.
I honestly believe this to be in full accord with GR and the known laws of physics and as such could be discussed in mainline forums.
If you believe I am wrong please be specific in stating in what way I am wrong. Generalizations are of no help.
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"An object with a large mass is travelling from dilated time to a less dilated time and it does that continuously. This is acceleration."
This is what any massive gravitating body does. It travels in space-time from a place where time has a certain time dilation factor to a place where time is less dilated (relative to a distant observer). This is acceleration.
Acceleration is measured as metres per second per second. If progressively a second becomes shorter (as referenced by a distant observer) then this is acceleration.
We normally think of acceleration as having both direction and rate of increase. Therefore an object cannot normally accelerate in all spacial directions at the same time. For a sphere to accelerate in all spacial directions at the same time it would seem to imply that it must expand. Obviously it does not. What it does is to accelerate through time.
An accelerometer placed anywhere on the surface of the Earth at sea level and pointing up will measure 1g acceleration. It measures acceleration because the passage of time itself is accelerating.
In free fall the accelerometer reads zero because it falls at the same rate as time dilates.
Gravity is often referred to as by far the weaker of the forces but we tend not to realize just how powerful gravity is. 1g the gravity that we experience on the Earths surface is seen to be considerable when you consider the space-shuttle develops just 3g acceleration. (Gravity is not strictly speaking a force but it is often convenient to refer to it as if it is.)
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Hi Mike,
Frankly I am totally confused of what you are talking about, if you could go into detail of few things it'll be more helpful.
But if you're saying that time dilation depends on gravity, its not proven yet. Little amount of time dilation is tested but seriously its not a huge difference where we can't say that error could be on experiment side. When Einstein talked about time dilation it was because he wanted to fix the speed of light, but if you fix the speed of light time has to dilate otherwise it doesn't make sense.
Lots of people say "time dilation" is needed for GPS to work but seriously these clocks on satellite are updated every second from ground stations so I don't think its possible to have a time dilation in these satellite clocks.
But it'll be great if you could explain your idea one more time, because I agree with time dilation but not depending upon speed but size, larger the size faster the time is, I have my reasons for that.
It'll be great to get your idea once more and if you could make it much more clear it'll be great.
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Hi Mike,
Frankly I am totally confused of what you are talking about, if you could go into detail of few things it'll be more helpful.
But if you're saying that time dilation depends on gravity, its not proven yet. Little amount of time dilation is tested but seriously its not a huge difference where we can't say that error could be on experiment side. When Einstein talked about time dilation it was because he wanted to fix the speed of light, but if you fix the speed of light time has to dilate otherwise it doesn't make sense.
Yes it is proven. We are well within experiment error bounds when we test gravitational time dilation - it is an effect that can be measured and fits the mathematical models which predict it.
Einstein did not want to fix the speed of light - he knew it was finite and wanted to show how that would fit into a coherent physics with relativity (ie same physics for all inertial frames).
Lots of people say "time dilation" is needed for GPS to work but seriously these clocks on satellite are updated every second from ground stations so I don't think its possible to have a time dilation in these satellite clocks.
Clocks in GPS satellites have to be compensated from time dilation due to relative velocity and differing gravitational potential - you can find the figures on the net. The fact that satellites 22000 km away can accurately be used to determine your position is fairly good evidence that the idea is correct
But it'll be great if you could explain your idea one more time, because I agree with time dilation but not depending upon speed but size, larger the size faster the time is, I have my reasons for that.
It'll be great to get your idea once more and if you could make it much more clear it'll be great.
Time dilation depends on relative velocity and difference in gravitational potential - if you want to posit something else you are going to need to fill in a huge amount of gaps left by those two ideas
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greeniemax
Imatfaal has pretty much answered your questions.
But it'll be great if you could explain your idea one more time, because I agree with time dilation but not depending upon speed but size, larger the size faster the time is, I have my reasons for that.
It'll be great to get your idea once more and if you could make it much more clear it'll be great.
If you mean by that the greater the mass the faster the passage of local time then that would be wrong. The greater the mass the slower the passage of local time as observed by a distant observer. This has been tested and found to be correct.
I have tried to make it as clear as possible whilst keeping it as short as reasonably possible. If you wish for me to clarity any specific points please ask.
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Hmm, so the event horizon of a black hole is the border where time dilation would slow down time to exactly the amount where light no longer has the time to escape with its constant velocity?
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Hmm, so the event horizon of a black hole is the border where time dilation would slow down time to exactly the amount where light no longer has the time to escape with its constant velocity?
c is still a constant velocity no matter how slow the passage of time. Or to put it another way, time adjusts in just the right manner such as to keep c constant.
Another way of looking at it is space is flowing into the black hole at the speed of light.
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Einstein said that gravity is acceleration.
To the best of my knowledge he never elaborated on that in simple and understandable terms.
That is what I have tried to do. At the start of this thread I said.
"An object with a large mass is travelling from dilated time to a less dilated time and it does that continuously. This is acceleration."
I then went on to explain in detail exactly what that meant.
Unfortunately I have had very little feedback from you all. Do I take that to mean that you all agree with me? Does my explanation fill in the missing gaps?
If you don't agree, I would like to hear your explanation as to why you think I am wrong.
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It would appear I am not alone in the thought.
"An object with a large mass is travelling from dilated time to a less dilated time and it does that continuously. This is acceleration."
I have just come across this
Gravity as Curved Spacetime
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"The trouble is that, in speaking of the earth's surface, we have again lapsed into thinking of acceleration in spatial terms. On earth, where speeds are small compared to the speed of light and the gravitational field is weak, it turns out that nearly all of our weight arises due to the warping of time, rather than space. What this means in practice is that gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space."
http://einstein.stanford.edu/SPACETIME/spacetime2.html
Coloured highlight added.
It does show that what I wrote was mainline (even if not understood to be mainline) and needn't have been moved to New Theories where it has generated little feedback.
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Is it this you're referring to Mike?
"While intuitively appealing, however, the rubber-sheet picture has its limitations. Mostly, these have to do with the fact that it allows us to visualize the spatial aspect of Einstein's theory, but not the temporal one. To see this, we need only remember that Newtonian gravity must be approximately valid, whatever Einstein says, and Newton tells us that bodies move in straight lines unless acted upon by a force. Why, then, do the orbits of planets around the sun on the rubber sheet appear so far from straight, if there is no attracting force reaching out through spacetime to tug on them? The answer is that planetary trajectories are very nearly straight — in spacetime, not space. The worldline of the earth, for example, resembles a stretched-out spiral whose width in space is only one astronomical unit, but whose length in the time direction is measured in lightyears! Another way to appreciate the importance of the "time" in "spacetime" is to apply the equivalence principle and ask whether the fact that we experience a gravitational field on the earth's surface is "equivalent" to stating that the earth's surface is continually accelerating outward.
Obviously not, for we do not observe the earth to grow larger! The trouble is that, in speaking of the earth's surface, we have again lapsed into thinking of acceleration in spatial terms. On earth, where speeds are small compared to the speed of light and the gravitational field is weak, it turns out that nearly all of our weight arises due to the warping of time, rather than space. What this means in practice is that gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space."
I find this one rather confusing? You can't split SpaceTime into 'components', and the assertion that 'gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space.' makes little sense to me?
They all go together, in a uniform acceleration your wrist watch will slow down according to the inertial observer and you will find a local gravitational potential. You might say that you 'warp' SpaceTime locally by accelerating, but the clock rate as well as the gravity is one joined thing, together. And they are observer dependent, meaning that for a 'clock' to be found to go 'slower' you will need to be at another 'frame of reference' observing that. When it comes to gravity that also has to be observer defined, as that local accelerating gravity exist at one positional place relative the local definition, versus another for the unaccelerated observer, using his definitions of a ruler and and a clock.
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clip
I find this one rather confusing? You can't split SpaceTime into 'components', and the assertion that 'gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space.' makes little sense to me?
yor_on
Have you read my first or preferably first and second posts in this thread where I have explained the ideas in detail?
It's a very simple idea. The Earth is continuously travelling from a place where time is dilated to a place where time is less dilated as observed by a distant observer. This is acceleration through time as time itself is speeding up. Acceleration is normally an increase in distance over time. That is how we normally perceive acceleration.
The conventional standard value at which things fall towards the Earths surface is 9.80665 m/s2. This can be re-phrased as the surface of the Earth accelerates outwards not in any spacial dimension but in the time dimension. The Earth remains the same size but as it travels from one instant in time to the next, the next instant is shorter. That's acceleration. The surface of the Earth accelerates at 9.80665 m/s2 (1g) towards any object (in free fall) above it.
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If you consider a test particle in its own empty universe.(modify. empty of matter but with energy.) The particle is stationary in the three spacial dimensions but is moving, accelerating in the time dimension or more correctly, space-time. I guess that could be re-phrased as anything that has mass cannot be stationary in space-time.
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Hi Mike
I like your idea and as you say it is a possible answer to better explaining gravity but I’ve has similar thoughts myself and one or two points occurred to me that pushed me back off the idea. I agree with points 1, 2, 3, and 5 in your opening paragraph but point 4 is where it gets a bit more complicated.
4) In physics, acceleration is the rate of change of velocity with time.
However, it can equally be a constant (or changing) velocity with a changing rate of time (changing time dilation factor.)
Now time dilation is a real thing as you say but gravity and time dilation do not appear to be variable in respect to one another i.e. time given GR will slow as proximity to mass increases but this is a relative constant, mass dictates time dilation not the other way round.
So is gravity caused by mass accelerating through space-time, no I don’t think so but it is a variable relative to velocity. The hard part is in appreciating the individual factors, Time, Gravity, and space/distance. If you view time speeding up as fewer time intervals for a set distance you have one result and if you view time as fixed and the relevant distance travelled for each interval as varying you get another. Is time fixed and space stretches or the other way round, or both at the same time.
Now I view distance as fixed and what we perceive as time varying but there is no definitive answer either way so I know my opinion is just as open to debate as yours.
If you consider a test particle in its own empty universe. The particle is stationary in the three spacial dimensions but is moving, accelerating in the time dimension or more correctly, space-time. I guess that could be re-phrased as anything that has mass cannot be stationary in space-time.
If you are considering an example of an empty universe as Einstein does in Special Relativity then a single particle can be stationery in Space-Time, you have to introduce a second reference point or particle, thats the relativity aspect of the theory. Time would stand still for a single particle in an empty universe given your example.
Hope that helps,
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If you consider a test particle in its own empty universe. The particle is stationary in the three spacial dimensions but is moving, accelerating in the time dimension or more correctly, space-time. I guess that could be re-phrased as anything that has mass cannot be stationary in space-time.
If you are considering an example of an empty universe as Einstein does in Special Relativity then a single particle can be stationery in Space-Time, you have to introduce a second reference point or particle, thats the relativity aspect of the theory. Time would stand still for a single particle in an empty universe given your example.
I should have said devoid of mass but with energy. Original post modified.
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Hi Mike
I like your idea and as you say it is a possible answer to better explaining gravity but I’ve has similar thoughts myself and one or two points occurred to me that pushed me back off the idea. I agree with points 1, 2, 3, and 5 in your opening paragraph but point 4 is where it gets a bit more complicated.
4) In physics, acceleration is the rate of change of velocity with time.
However, it can equally be a constant (or changing) velocity with a changing rate of time (changing time dilation factor.)
Now time dilation is a real thing as you say but gravity and time dilation do not appear to be variable in respect to one another i.e. time given GR will slow as proximity to mass increases but this is a relative constant, mass dictates time dilation not the other way round.
So is gravity caused by mass accelerating through space-time, no I don’t think so but it is a variable relative to velocity. The hard part is in appreciating the individual factors, Time, Gravity, and space/distance. If you view time speeding up as fewer time intervals for a set distance you have one result and if you view time as fixed and the relevant distance travelled for each interval as varying you get another. Is time fixed and space stretches or the other way round, or both at the same time.
Now I view distance as fixed and what we perceive as time varying but there is no definitive answer either way so I know my opinion is just as open to debate as yours.
See post number 8 in this thread for confirmation of point 4.
I never said they were.
I agree, I never said it was the other way around.
See post 8 in this thread for confirmation that
"gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space."
http://einstein.stanford.edu/SPACETIME/spacetime2.html
Time is variable. That's not open to debate.
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Crossed hairs it would seem,
you wrote "it can equally be a constant (or changing) velocity with a changing rate of time (changing time dilation factor.)" in point 4.
It can be a constant velocity with changing time or changing velocity with constant time, that’s open to debate ! It cannot be changing velocity and changing time simultaneously or gravity would fluctuate everywhere and cosmology would be a crazy thing to look at. Likewise they both can't be fixed because its been proved otherwise with things like the atomic clock tests.
Have you considered the "cosmological constant", this essentially would be a reference point by which Space-Time can be measured as accelerating and is in line with your point of, if I understand you. The Cosmological Constant has just received a little press because it may have been proved or is at least far more likely...
http://uk.news.yahoo.com/einstein-proved-over-universe-095658382.html
Not a great link but you can go from there, its one of those topics opinions change constantly and this is about as up-to-date as I could find on the fly.
Also I'm sure your only using that link to Stanford Uni as an example but its one of the most basic descriptions of Space-Time I've ever read.
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I'm not sure, but what they might mean is that the gravitational potential you get form accelerating uniformly at one gravity doesn't have the same implications as one gravity on the surface of Earth, as I read it. And from there they ask that if this isn't so? Then what 'join' the two reference frames?
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"On earth, where speeds are small compared to the speed of light and the gravitational field is weak, it turns out that nearly all of our weight arises due to the warping of time, rather than space. What this means in practice is that gravity on earth is "equivalent" to acceleration mostly in the sense that clocks on the surface run more slowly than clocks in outer space."
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But if you define 'gravity' from a local point of view, as you using any weighting mechanism to measure your weight locally, then the 'gravity' is exactly equivalent.
At one G accelerating, will the time dilation measured from a 'inertial frame' be equivalent to the time dilation measured on Earth, as measured from that same 'inertial frame' :)
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Crossed hairs it would seem,
you wrote "it can equally be a constant (or changing) velocity with a changing rate of time (changing time dilation factor.)" in point 4.
It can be a constant velocity with changing time or changing velocity with constant time, that’s open to debate ! It cannot be changing velocity and changing time simultaneously or gravity would fluctuate everywhere and cosmology would be a crazy thing to look at. Likewise they both can't be fixed because its been proved otherwise with things like the atomic clock tests.
Have you considered the "cosmological constant", this essentially would be a reference point by which Space-Time can be measured as accelerating and is in line with your point of, if I understand you. The Cosmological Constant has just received a little press because it may have been proved or is at least far more likely...
http://uk.news.yahoo.com/einstein-proved-over-universe-095658382.html
Not a great link but you can go from there, its one of those topics opinions change constantly and this is about as up-to-date as I could find on the fly.
Also I'm sure your only using that link to Stanford Uni as an example but its one of the most basic descriptions of Space-Time I've ever read.
Is it open to debate. Acceleration is change in velocity over change in time. If either of them changes in respect to the other then that is acceleration. So the velocity can be constant or changing, so long as the time dilation factor is changing then that is acceleration. I don't see what is open to debate about that.
It cannot be changing velocity and changing time simultaneously or and gravity would does fluctuate everywhere in the Universe. The Universe is a crazy thing to look at and it's even more crazy as we do not 'see' time or gravity. I believe if we could see time and gravity the Universe would make far more sense. By analogy when we look at a two dimensional geological map we see two dimensions but what is represents is three dimensional. When we look at a galaxy we are not seeing an object in normal 4 dimensional space-time. (We normally see something within a local time frame. A galaxy does not have a single time frame.) A galaxy is so large that it has a differential gravitational potential across its radius. This means it has a differential time dilation gradient across its radius. Because it is so large what we see is part of it's 'world line' smeared over space-time. I personally believe it is this that makes the picture difficult to interpret.
Gravity does not fluctuate (essentially) on the Earths surface as the Earths acceleration through time or space-time is constant.
I used that link as it is the only simple description of gravity that is in line with GR that I have ever come across. Remember I am not trying to propose anything new in this thread only to explain in simple terms what gravity is and what Einstein actually meant when he said gravity is acceleration.
As you said
"Also I'm sure your only using that link to Stanford Uni as an example but its one of the most basic descriptions of Space-Time I've ever read."
Yes it is and it explains in simple terms exactly what gravity is. What I have done is to elaborate on that in detail but I did it before being aware of the article or having read or being aware of anything similar elsewhere.
Basic is good. Occam would have been well pleased.
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At one G accelerating, will the time dilation measured from a 'inertial frame' be equivalent to the time dilation measured on Earth, as measured from that same 'inertial frame' :)
Don't all other clocks run slow from your inertial frame? The greater your velocity the greater the time dilation factor.
It seems to me that a clock (in a spaceship) accelerating at 1g is not going to keep the same time as a clock stationary on the surface of the Earth as the Earth accelerates at 1g. A clock accelerating at 1g (through space) is gaining velocity. The Earth accelerating at 1g (through time) is not gaining velocity.
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It's quite easy to prove them different Mike so you're perfectly correct. They are not the same in form of time dilation, as observed from some thought up point in SpaceTime. And in fact, as all points are equivalent there can be no exact definition of the arrow, except, if using a strictly local definition in which case 'the arrow' always will be the same for you, no matter where you go, or how fast relative something else.
What makes 'time dilations' are two things. Gravity/mass/accelerations and relative uniform motion. Motion is split into relative uniform motion, and then accelerations which locally becomes ones 'gravity'. They both warp and twist the room time geometry, differently depending on the observer being 'inside' the motion acceleration mass versus 'outside' observing it, with the added effect that a acceleration also locally becomes a gravity.
When you look at SpaceTime you have two choices, either you see it as one whole undifferentiated thingie or you decide that locality rule. If you use the first you get 'streams of time' in the 'ocean' of SpaceTime joined conceptually by Lorentz transformations. If you use the later you get one arrow, same for all observers. The only thing differing it being where you are, observing the rest of your SpaceTime/universe, as defined from your clock and ruler.
The first way of defining it also will find that all positions are observer defined, gravity will also be observer defined, even the constant 'c' can from some points of view become observer defined as in different accelerations. From the view of locality all definitions must go out from the room time geometry you exist in, and they will all be as true locally. In that view 'c' becomes a constant defining/explaining why we see both time dilations as well as Lorenz contractions. Lorentz transformations naturally follows from that constant being the same everywhere, and 'anytime'.
And in the end it all becomes a question of geometry, mass/energy, 'motion' and radiations constant. In that universe 'locality' describes, radiation is what binds it seamlessly for all observers, although 'distorted' relative each other.
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And if mass is equivalent to energy, then that has to be the ultimate description of 'something', joining it all into one definition.
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Eh, need to correct myself.
Inertia is a resistance to motion but it is as well a resistance to 'change'. That means that in a (relative) uniform motion (in space) inertia will act on anything changing the equilibrium presented by that 'motion' as defined by the observer.
Inertia is weird :)
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I said in post 17 of this thread
" Acceleration is change in velocity over change in time. If either of them changes in respect to the other then that is acceleration. So the velocity can be constant or changing, so long as the time dilation factor is changing then that is acceleration."
velocity v = distance d / time t.
Acceleration a = ( Vf - Vi ) / t.
If either v, d or t change then this is acceleration.
We normally only associate acceleration with the SPACIAL dimension of space-time not the TIME dimension of space-time.
Example 1
As a space-ship accelerates to approaching light speed. A distant observer would see an on board clock as time dilated to almost zero passage of time. As speed is at a maximum, so the passage of time is at a minimum. A distant observer sees the ship travelling at almost light speed.
Example 2
A space-ship entering the event horizon of a black hole is travelling at light speed toward the singularity in it's center. This is due to the EH of the black hole accelerating at light speed toward the space-ship. A distant observer sees the ship to be stationary.
Both examples demonstrate acceleration.
The first example is familiar to us, it is what we normally think of as acceleration.
The second example, whilst being extremely familiar as it is gravity, is not intuitive. We do not recognize it as acceleration.
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It's a question I wonder about too Mike. What is a ultimate 'speed' of something gravitationally in-falling through the Event Horizon? It can't really be 'c' as that is a limit. But it is also so that I can assume 'uniform motions' infinity close to 'c'. But if we consider it some more we will notice that for two infinity's to merge as a 'speed' at 'c' for mass, relative a Black Hole, it must then be defined infinitely close to its 'center' as it is only there the mass becomes 'infinite'.
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It's a question I wonder about too Mike. What is a ultimate 'speed' of something gravitationally in-falling through the Event Horizon? It can't really be 'c' as that is a limit. But it is also so that I can assume 'uniform motions' infinity close to 'c'. But if we consider it some more we will notice that for two infinity's to merge as a 'speed' at 'c' for mass, relative a Black Hole, it must then be defined infinitely close to its 'center' as it is only there the mass becomes 'infinite'.
It seems reasonable to suppose that it continues to accelerate from our perspective but it is stationary in time at the EH. No material object can accelerate above c for various reasons. The only way it can be perceived to accelerate above c is for the arrow of time to reverse direction. Although GR says that no object with mass can accelerate up to the speed of light, this only seems to be correct if the acceleration is in the SPACE aspect of space-time. The EH of a black hole accelerates at the speed of light but the acceleration is in the TIME aspect of space-time. The acceleration of the black hole is censored from view by the EH.
A way of accounting for acceleration toward the singularity in a black hole is by time reversal. If the arrow of time within the EH reverses so does charge and parity then it would be possible to consider the black hole to be made of antimatter.
If we substitute the word matter for the more commonly used word mass then GR remains intact. Mass is often used when referring to both matter and antimatter by assuming that both matter and antimatter have positive mass. This is not proven.
Looked at from this perspective black holes obey the normal laws of physics.