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Black Hole Fall





theotex
Who knows enough on relativity theory to describe the following experience :

A stone is falling toward a black hole. As its speed gets nearer to the speed of light, the mass of the stone increases ; but also, and in the same proportion, the attractive strength exerted by the black hole on the stone. For instance when the stone has doubled its mass, it's weight has doubled too.

So my question : is the movement equation of this stone going to be the same as in newtonian mechanics ? what will be the final speed of the stone ?
Bikerman
No. You have made an elementary mistake...

The mass remains constant in the inertial frame occupied by the stone. The mass only changes relative to a non-inertial observer.,

The gravitic attraction does increase, of course, with the square of distance, but the relativistic effect on velocity diverges more and more from Newtonian predictions as time (local subjective) passes. The final speed will be a high fraction of c. The exact value will depend on the mass of the BH.
theotex
I didn't get your answer.

As an observer I place myself in a galilean frame, so I see the mass of the stone increasing, according to a well known law. Of course the attraction on the stone increases when the distance to the black home diminishes, but that is not the point. It increases too because the mass (in my galilean frame) increases.
What would the equation x(t), of this movement in my frame ?
Bikerman
The stone doesn't increase in mass in its own frame. The attraction acts in the stones frame, not your observer frame, therefore there will be no increase in gravitational force, other than the one expected as r changes.
theotex
So what you are saying is that the gravitational attraction doesn't depend of the body speed ? How do you prove that ? In its own frame the black hole sees the stone with its increased mass and so why wouldn't it attracted it more ?
Bikerman
From your observer frame the stone will slow and slow until it stops at the event horizon. It will then dim until invisible to you.
Bikerman
theotex wrote:
So what you are saying is that the gravitational attraction doesn't depend of the body speed ? How do you prove that ? In its own frame the black hole sees the stone with its increased mass and so why wouldn't it attracted it more ?
Thats a wrong view of gravity. The BH isn't a conscious agent and it can't increase its 'attraction'. Picture gravity simply as the travel of the stone along the geodesic and then you have a workable image.
theotex
Of course the BH is not conscious that was a way of speaking, and I am not convinced it's attraction is going to remain the same as in Newon mechanics. Well, I supposed I can wait a bit before somebody gives the exact x(t), says in BH frame... and maybe haveI reach my personal horizon of 5 posts before subdomain access.

Thank you.
Bikerman
x(t) in the frame of the bh? The frame of the BH is ill defined and has no real meaning here. You can talk about a frame at the event horizon, or some other well defined point, but I don't think you can talk about the 'BH' in such terms because the singularity doesn't have a definable frame wrt anything in spacetime.
badai
when you failed classic physics (mass vs weight and speed vs acceleration) just don't talk about relativity.
Bikerman
Yes, the problem comes from mixing the two in the same problem.
You EITHER do it via Newtonian dynamics - and get the wrong answer - OR you do it via General Relativity and get (approx) the right answer. You can't start with a relativistic model and then introduce Newtonian elements (or vica-versa) and expect to get a sensible answer.
Hence in Newtonian physics we take gravity as a force (f=ma), but in GR we don't - gravity is the distortion in space produced by mass.
spinout
Hm, is there a threshold in mass causing a distortion in space?? In smallness I mean...
kelseymh
spinout wrote:
Hm, is there a threshold in mass causing a distortion in space?? In smallness I mean...


Not in GR. It is a classical, continuous theory. The smaller the mass (technically, the smaller the components of the stress-energy tensor), the smaller the curvature, but there is no threshold effect.
Bikerman
Which is, perhaps, indicating a problem with GR? Basically (and correct me if I'm wrong - I'll welcome it, since I'm at the edge of anything I can claim to actually 'know') GR is a 'smooth' theory - continuous - in IT we'd probably call it analogue ( Smile ) whereas QM is (as the name indicates) quantised - chunky - comes in discreet bits. My semi-educated feeling is that spacetime MUST quantise and can't be smooth 'all the way down'* . Would you care to ventury an opinion Mike (I won't tell the Science Police, promise).

*Reminds me of the Hawking story in 'A Brief History':
Hawking wrote:
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever," said the old lady. "But it's tortoises all the way down!"
kelseymh
Bikerman wrote:
Which is, perhaps, indicating a problem with GR? Basically (and correct me if I'm wrong - I'll welcome it, since I'm at the edge of anything I can claim to actually 'know') GR is a 'smooth' theory - continuous - in IT we'd probably call it analogue ( Smile ) whereas QM is (as the name indicates) quantised - chunky - comes in discreet bits. My semi-educated feeling is that spacetime MUST quantise and can't be smooth 'all the way down'* . Would you care to ventury an opinion Mike


I was avoiding this issue, because it will only appear to "vindicate" the crackpots who don't actually understand what they're talking about.

The issue with GR is _not_ that there's no minimum length scale. There isn't one in QFT, either -- position and momentum _are_ continuous variables, but their operator commutation relation leads to a limit on their simultaneous measurement precision.

The conflict when trying to quantize GR is that it is not renormalizable. If you try to apply second quantization to spacetime itself, you get infinities which cannot be eliminated by taking the 4-epsilon dimensional limit.

There are multiple good, and renormalizable, approaches to work around this, including string theory, loop quantum gravity, causal triangulation, and others. They all reduce to GR in the appropriate limit (as they must!), and they all make definite, and different, predictions about the behaviour of gravity on both small and cosmological scales.

At the moment, we don't have sufficient experimental precision to distinguish among these approaches, neither with cosmological nor bench-top data. All of our results to date are fully consistent (at the part per trillion level!) with classical GR.
Bikerman
Yes, I should have realised that this might attract the less sane posters....I doubt they will follow this, though, since there are some big words Smile
I presume GR predicts that gravity will continue the inverse square relationship down as r->0, whereas the other hypotheses don't necessarily....I remember trying to plough through a paper on string theory to try and get an overview (by Ed Witten), but the maths was fiendish and well beyond my current level - that's one main reason I'm currently sat with the Penrose tome, working though and trying to get enough background for another attack on it Smile
spinout
Of course there is a threshold in the universe. But I think it is at a very very little bit mass...
spinout
The threshold is 10^-40 % of the mass of a proton to my calculation. So a particle equal or under that size in mass will not distort space.

Well I am not saying that is of any use.
kelseymh
spinout wrote:
The threshold is 10^-40 % of the mass of a proton to my calculation. So a particle equal or under that size in mass will not distort space.

Well I am not saying that is of any use.


Citation needed. Are you computing the Planck mass?
spinout
Yes, citation needed. But I am just a enthusiast so I need to think if I could upgrade the mass a bit. still thinking actually, hehe.
Yes, planck mass of course. But where does it get "uninteresting" to the space? So I took an order below what energy would needed for space to response (Schartszchild criteria)... Hm, still thinking...
I also mentioned the proton, and that is also a problem. Some new problems have come up in the definition, so I took the Haramein definition of it - of course this will fit since he defines it as meeting the scharzchild criteria already , hehe making it easy- So to his definition 10^-39 % will do actually. Anyhow the weight of a proton is not interesting to this, so 10^-40 % of any proton mass will do since the biggest mass of the proton anyone have come up with responds to th 10^-39%...

Hm, I will come back with the ecaxt numbers
kelseymh
spinout wrote:
Yes, citation needed. But I am just a enthusiast so I need to think if I could upgrade the mass a bit. still thinking actually, hehe.
Yes, planck mass of course. But where does it get "uninteresting" to the space? So I took an order below what energy would needed for space to response (Schartszchild criteria)... Hm, still thinking...
I also mentioned the proton, and that is also a problem. Some new problems have come up in the definition, so I took the Haramein definition of it - of course this will fit since he defines it as meeting the scharzchild criteria already , hehe making it easy- So to his definition 10^-39 % will do actually. Anyhow the weight of a proton is not interesting to this, so 10^-40 % of any proton mass will do since the biggest mass of the proton anyone have come up with responds to th 10^-39%...

Hm, I will come back with the ecaxt numbers


What exactly are you talking about here? This looks like an awful lot of random sciencey-sounding words strung together into meaningless sentences.
Josso
Isn't there a section about this in a brief history of time?
spinout
What? I am not english speaking! Have some respect for that...
Bikerman
No, sorry, that won't cut it. I know English is not your first language but your English is pretty good. This is just bullshit - in whatever language.
spinout
Hm, I begin to think I am a bit ahead on the scale! If it is hard to follow Cool Still I got the 2nd lowest grade in English. So , ha, my english teacher might have been wrong!
Bikerman
No, as I have previously said, you are using the terminology and pseudo-babble of a charlatan - Haramein - so it is not at all surprising that it results in gibberish, since it is gibberish to start with.
spinout
Yes, my idea was based on Harameins work on how the space structure works. And the assumption that there is a certain amout of energy needed to make an impact on "space". Under that, well there is no impact and there is a threshold.

Yes a bit far fetched ... but I have another good point coming up, this time about the casimir effect gone out of sight in the lower regions... I'll be back tomorrow!
kelseymh
spinout wrote:
Yes, my idea was based on Harameins work on how the space structure works. And the assumption that there is a certain amout of energy needed to make an impact on "space". Under that, well there is no impact and there is a threshold.

Yes a bit far fetched ... but I have another good point coming up, this time about the casimir effect gone out of sight in the lower regions... I'll be back tomorrow!


Your points are not good, nor are they science. Using technical terminology without understanding sounds impressive, but is rather a clear demonstration of ignorance.
Bikerman
Yes, please don't bother. I was already persuaded that this is meaningless gibberish, and since that view seems to be shared by the most highly qualified and experienced user in this field of study, then it goes from persuaded to convinced.
I can't bear to watch Haramein himself for more than a brief period because he offends me at several levels - mainly the one about talking crap and pretending to be an authority. I really do NOT want his nonsense appearing here where I can't avoid it. It isn't science so it can't go here. You could post it in P&R if you really insist, but personally I would post it up Harameins arse - it would, at least, provide some temporary slackening in the volume of material travelling the other way.
spinout
My ideas are exclusive from Haramein. Why post someone elses ideas and take credit for it? Not my style. Hm, I have not read the latest paper haha,,,

This is the scenario here: I have an idea like "the earth is round and not flat because since the shadow of the earth on the moon is round" and the it is gibberish since it don't fit in the life on this planet and It is a good point but it is not science and it is a clear demonstration of ignarance a.s.o. Still, I am sure that the earth is round and it is worth to be told, atleast in a little forum... Is it so tuff to here I got an idea the earth is round?

I have finally got 2 flaws of Haramein to present! I have listened for hours before I... But i suppose you not want to here them.

hehe, I found another one claiming the universe is expanding in an acceleration before the nobelprice was delivered, David Ash. Some brittish guy, but I think he was cool saying the rather prefers the inch system than the metric... Is David Ash as annoying as Haramein? Atleast Haramein presents some papers...
Bluedoll
Bikerman wrote:
...It isn't science so it can't go here...
That makes sense to me and reasonable except in this thread 90% of it has nothing to do with science. Question
Bikerman
I presume you mean the argument about Haramein and his 'work'? If so then I agree but from time to time it becomes necessary to clear-up what is and what is not within the bounds of science and where such a discussion does not sidetrack a thread needlessly then I am happy for such discussion to be held publicly in these forums.
duytam28
Since black holes that aren’t located anywhere near anything are obviously hard to find, the astronomers focused their attention on X-ray binaries. These are star systems consisting of a star that’s located near a black hole. As the black hole strips away matter from its companion, huge bursts of X-rays are emitted – which is what the astronomers are looking out for.

When the astronomers identify an X-ray source they think might be an X-ray binary, “then we use the Hubble Space Telescope to see if we can find it in visible light,” wrote lead researcher Robin Barnard in a blog post. “The optical light is linked to the X-rays, so that the true counterpart to the X-ray transient should be visible in the first observation, but not in the second one; we can subtract the second image from the first one, making such changes clearly visible.”
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