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Black Holes - Spinning faster than light?

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When a massive star collapses in on itself, the resulting neutron star is spinning extremely fast. Scientists liken this fact to how ice skaters tuck their arms in while spinning to make themselves spin faster.

It got me thinking... Is it possible that supermassive stars begin spinning faster than light once they collapse far enough in that brief, cataclysmic formation of a black hole? Could this be one of the reasons that the laws of physics seem to just give up where black holes are concerned?

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the reason black holes exsist is because their escape velocity >c. we can measure the spin of black holes and they don't go faster than light

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15 minutes ago, insert_name said:

the reason black holes exsist is because their escape velocity >c. we can measure the spin of black holes and they don't go faster than light

Do they take time dilation and its effects on our observation into account?

This could get really mathematical really quick. :confused:

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Well... So yeah, it gets mathematical. Thing is, a rotating black hole "drags" the space around it. This means that the accretion disk can appear to rotate FTL really close to even horizon as it passes through the ergosphere. It's already traveling close to speed of light in its local frame, and you add frame dragging to it and you get an FTL total. Of course it's a useless kind of FTL that you can't do anything fun with unless you manage to cross into event horizon and then out again, but then you already have an FTL drive to pull it off to begin with.

Black hole itself, on the other hand, doesn't really rotate. That's a tricky one to explain, but it's a bit like an electron spin. It has all the qualities of a rotating object, but it doesn't have dimension necessary to actually rotate. Ground state of a rotating black hole is believed to be a ring singularity. That is a 1D object. A ring with absolutely no thickness. And it is perfectly uniform around that circle, except for whatever phase shift it needs to accumulate for the angular momentum. You can take that angular momentum and divide it by mass and radius, and then you will get some sort of a stupid number that looks like speed, and yeah, it will be a ludicrously large number. But it won't really have anything to do with what we think of as speed in physics. In order for there to be a speed, there has to be a signal group propagation, which implies lack of symmetry, and then it's not a singularity anymore. So yeah, doesn't really rotate.

But accretion disk is made up of actual matter, and that matter is traveling at FTL speeds through the ergosphere of a rotating black hole. For all the good it does anyone.

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And then there is the concept of relativistic mass increase, which some proponents defend and others reject, but if true it basically means that as the object's speed increases, its mass also increases and reaches infinity at c, meaning that no object with mass can travel at c.

http://isites.harvard.edu/fs/docs/icb.topic1214842.files/11lev-okun-on-mass.pdf

Black holes are tricky, but I wouldn't say they get a pass on breaking the laws of physics. They may be using some loopholes, though.

Edited by Shpaget

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Does it mean that any particle, orbiting a blackhole, when reaching the event horizon gets a galaxy mass for an outside observer?

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3 hours ago, kerbiloid said:

Does it mean that any particle, orbiting a blackhole, when reaching the event horizon gets a galaxy mass for an outside observer?

That is the problem with the term "relativistic mass", the particle doesn't gain any mass, just energy.

In special relativity, the energy of an object is expressed as E = gamma*m*c^2 , where gamma depends on the speed (and increases to infinity, if the speed of the object approaches the speed of light), m is the mass of the object (in the classical sense) and c the speed of light.

Any particle that orbits a black hole orbits at a ridiculously high speed, which means that it has a ridiculously high energy.

The "relativistic mass" is defined as M = gamma*m. The advantage of this notion is that the famous E = M*c^2 holds also for moving particles and in general it simplifies the formulas. However, M is some kind of mass that depends on the speed of the particle in the reference frame of the observer, i.e. it is a mass that is not constant and, even worse, it depends on the position you are observing it from. That is why some physicists accept the notion of "relativistic mass", while others reject it.

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Yes, I understand this. But isn't the relativistic mass felt by an outside observer also as increased gravitational mass?

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19 minutes ago, kerbiloid said:

Yes, I understand this. But isn't the relativistic mass felt by an outside observer also as increased gravitational mass?

AFAIK you are just covertly asking if matter falling into black hole can add a significant mass to pull more matter on.  A mass that that would disappear the moment it crosses event horizon? 
 

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37 minutes ago, kerbiloid said:

Yes, I understand this. But isn't the relativistic mass felt by an outside observer also as increased gravitational mass?

That is a very good question, never thought of that.

But I guess the answer is no. Imagine a particle with a speed very close to c. Its mass would be close to infinite. Infinite mass would lead to an infinite gravity well...

But I'm no expert...
 

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8 hours ago, kerbiloid said:

Does it mean that any particle, orbiting a blackhole, when reaching the event horizon gets a galaxy mass for an outside observer?

Read what he said, when they pass the event horizon, from our perspective universe, the particle ceases to exist and become part of the singularity.

Or let me put it to you like this. Imagine you have a perfect cube of empty space-time and you could move it where you wanted to, now imagine if you could push that cube of empty space toward a black hole, as it approached the event horizon 1 of its dimensions would shrink to nothing (quantum space time intercellular distances would only be relevant in 2 dimension, a curvature on the surface at the event horizon) as it touched the event horizon its time dimension would fade (in other words watching a clock on the object slow and then stop, just like a photon it would no longer age), and as it crossed the horizon its 2 remaining dimensions would fuse leaving one dimension. As you precede to the event this has consequences, because your 3 dimension fill with quantum foam and since this alters your perception of distance your eyes percieve your feet and the top of your head moving away from you at the speed of light, eventually your body parts stretch out and then vanish. 

This is in essence the communication problem, there is a belief in quantum mechanics that all starting states can be reconciled with events in the future, that system information is propagated forward in time, but when information crosses the black holes event horizon the information is seemingly lost, but through the processes of quantum space-time at the boundary and Hawkings radiation the information is preserved. Since we cannot see into a black hole from an observer its a quantum singularity, which means its one-dimensional, but the radiation that comes from a black hole emanates from the shell representing the event horizon, this is a form of communication. Its somewhat a contradication and somewhat not, the information at the surface is not due to the dimensionality of the information inside, simply the amount of energy the shell is a result of the energy within. The observable shell is not shaped by the shape of things inside, those things exist in a non-observable sub-universe, but the position and shape is due to the center of energy of that non-observable system and can be represented by a singularity floating around in 'our' space-time (oxymoron but useful since the differences in motion outside of the black hole are trivial relative to the space-time at the event horizon).

Another thing to remember, black holes curve space time, this creates alot of contradictions, so there are alot of guesses about what goes on inside of a black hole. If we follow the trend at the even horizon your XZ dimensions eventually shrink its as if you become a conical strand of spagetti that shrinks to nothing as you merge at the center. As you the internal observer, cross the horizon your lines compress into a point roughly at c, This create contradictions on how space-time should behave, particularly at the quauntum level, these contradictions can best be handled by creating an unknown physical state such as the starting state of the universe. In other we arge given an universal starting state and inflation then Universe. By the same token we can argue given a intense warping of space time then we have end state, black hole, and you don't have to muck around with the contradictions internal structures within our laws of physics. 

 

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2 hours ago, kerbiloid said:

Yes, I understand this. But isn't the relativistic mass felt by an outside observer also as increased gravitational mass?

"Relativistic Mass" is only a concept within the theory of special relativity, it is only a theoretical concept (to simplify formulas) and has no real consequences. In particular, it is not the classical mass that creates gravity. That is also why about half of the physicists don't use this notion, since, despite its capability of simplifying formulas, it confuses people.

Also special relativity doesn't include a theory of gravity, it only describes the relative movement of non-accelerated objects (as in no force is applied to them).

2 hours ago, lugge said:

That is a very good question, never thought of that.

But I guess the answer is no. Imagine a particle with a speed very close to c. Its mass would be close to infinite. Infinite mass would lead to an infinite gravity well...

But I'm no expert...

Its relativistic mass would be close to infinity, but its classical mass not.

However, telling how gravity behaves in the context of special relativity is impossible, since gravity is a form of acceleration and special relativity doesn't tell us anything about accelerating objects. Acceleration is what general relativity is all about, but unfortunately I don't have a single clue about it.

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3 hours ago, radonek said:

AFAIK you are just covertly asking if matter falling into black hole can add a significant mass to pull more matter on.

No, I'm covertly asking why such gravity doesn't attract all around. From observer's pov it stays over the event horizon forever, and its (relativistic) gravitational mass permanently grows.

https://www.quora.com/Relativity-physics-Does-relativistic-mass-have-gravity

Edited by kerbiloid

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Matter dropping into a black hole follows a geodesic trajectory and should thus not change its energy at all.

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