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Marn

Any physics nerds in here?

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I'm not a physicist so my entire question is probably completely flawed to begin with, but I'll ask it anyway.

 

If spinning black holes spin at a fixed rate and angular momentum is conserved when a star collapses into a black hole, shouldn't that mean that whatever is at the center of a black hole would have some sort of measurable diameter that corresponds to how fast the black hole is spinning? After all, if what's there is an infinitely dense point, wouldn't that mean the black hole would have to spin infinitely fast?

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yes, it's speculated that if a black hole is spinning, its singularity would be a ring rather than a single point. look up 'ring singularity' for more info.

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Please consider that a Singularity is a mathematical concept wich shows that our current understanding of physics is insufficient, a Black Hole Singularity represents the moment in time in wich the mass of the entire Black Hole colapses onto you after crossing the Event Horizon.

 

Some physicists theorize that whatever lies at the center of a Black Hole is the size of a plank lenght, the smallest measure unit in the universe, so a singularity or as Xcalibur said a ring singularity is that small.

 

No, it wouldn't spin infinitely fast, a black hole has mass, and any object with mass needs an infinitely exponential amount of energy to move as fast as light or faster, black holes can spin a maximum of 99% the speed of light.

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8 hours ago, Doominator2 said:

Hey guys did you know that the unit for acceleration is m/s^2?

  • Velocity is the rate of change in position: m/s.
  • Acceleration is the rate of change in velocity: m/s^2.
  • Jerk (also called jolt in the UK) is the rate of change of acceleration: m/s^3.
  • Jounce is the rate of change of jerk: m/s^4.
  • The amount of force required to accelerate 1 kilogram at the rate of 1 m/s^2 is called a Newton: kg*m/s^2.
  • The amount of energy required to apply 1 Newton of force over the distance of 1 meter is called a Joule: kg*m^2/s^2.
  • The amount of torque you get from applying 1 Newton of force at a distance of 1 meter from the fulcrum is called a Newton-meter, also kg*m^2/s^2, but measuring something completely different and not interchangeable with a Joule.
  • A Joule is also the energy of 1 Watt of power in 1 second: W*s, which means that a Watt is a kg*m/s^3.

To be honest, I looked up what the rate of change of jerk was, and also the fact that a Joule is a Watt times a second.  The rest I already knew.

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That is an interesting question.  I probably know less than the people who posted here, but some thoughts:

1) Every object has angular rotation.  Or rather, every independent, inanimate object has rotation.  This is caused by gravitational interaction with external particles and the electromagnetic forces.  The "quark soup" at the planck scale prevents anything from being entirely motionless.  From sub-atomic particles to clusters of galaxies, everything is spinning.  I think this is caused in part by the electromagnetic force -- that the field of electricity is manifested in a perpendicular circular field.

2) When high-mass stars collapse to a neutron star after a supernova, the atoms are stripped of their electrons and compressed to only the material in the nucleus.(thus the neutron moniker).  When this happens, the collapse makes the star rotate faster and faster.  Imagine a 50 mile sphere rotating at hundreds of times a second.  The surface of that sphere is rotating extremely quickly -- like a 10th of the speed of light.  Eventually, if more mass is added, the star will collapse to a black hole.

3) There isn't a "center" object of a black hole, at least as I understand it.  There is an object that is compressed by gravitational pressure to a density that prevents particles and electromagnetic radiation(light, etc..) from escaping; that object IS the black hole.  That's it. There _is_ also an event horizon gravitational "wake" phenomenon that accompanies the black hole.  As electromagnetic waves and particles are gravitationally attracted to the black hole, they are pulled harder and harder, faster and faster into the actual black hole through this 'wake' of the event horizon.  But let's not confuse the wake with the actual event horizon(which is the point where the gravitational pull is strong enough to prevent even light from escaping).

4) If the Earth instantly became a black hole.  It would be reduced to the size of a walnut or so.  We, 7000 miles from the walnut-sized black hole, wouldn't be pulled in any faster or harder than we are now(although, you would still fall all the way down into it).  The gravitational constant at what was the Earth's surface would still be 9.8 m/s/s as it is currently.  

The super-massive black hole at the center of the Milky Way galaxy is so large and massive that the event horizon wake would be large enough that, according to Stephen Hawking, you could start to fall into it, even through the event horizon, without knowing it(because of the laws of relativity).

5) The size of a black hole is proportional to its mass.

 

But to answer your question, I don't think anyone knows the relationship between their motion and their mass.  From their cause of creation or what type of black hole they are.  I'm skeptical if we will ever know.  They are very difficult to monitor or test... and any historical data would have to be based on large lengths of time monitoring. 

The intriguing part of your question lies with the conservation of energy and angular momentum.  Why this is currently unsolvable is because the laws of relativity don't cover infinites.  That is exactly why we don't know what happens inside a black hole.  The laws of physics as we know them don't explain the details of a black hole, or before 10 to the -43 seconds after the big bang.  It is beyond our understanding.

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