Well, here comes another black hole question from yours truly. I'm sure everyone is surprised ;)
So I've heard arguments from physicists before, saying that the planet near a blackhole in Interstellar would be unstable, or bathed in lethal radiation from the accretion disk, etc. But it just dawned upon me that it should be flat out impossible for it to be there.
Of course, that's calculated from my position of not understanding most of GR, so I might be wrong. (I know, it surprises me too.;)) If anyone knows better, please do correct me.
So for a Schwarzschild kind of black hole, the time dilation effect in relation to a far far away observer is the square root of (1 - 2GM/rc2). So as you get closer to the Schwarzschild radius, that approaches infinity.
Black holes also have a photon sphere, i.e., a radius under which even photons can't maintain a stable orbit. In the recent photo of a black hole, yeah, that was what the black blob in the middle was. It wasn't the event horizon itself.
That radius, again for a Schwarzschild kinda black hole, is 3GM/c2.
Thing is, if you substitute the latter formula into the former, you're still at VERY tame time dilation.
Ok, so at this point I should probably add SR time dilation, since that planet or its star would be orbiting around the star, not hovering in place. And the thing is, we still have some thousands of times worth of time dilation for that to explain. The OVERWHELMING difference in how fast time flows would in fact be from it moving incredibly close to the speed of light, rather than the black hole itself.
I.e., that planet wouldn't be somewhere at the outer edge of the accretion disk. It would be right at the INNER edge of the accretion disk, and at that, quite spaghettified.
So am I wrong there?
Also, obviously I'm not qualified to touch the maths for a ROTATING black hole with a 10 lightyear pole. Which the one in Interstellar probably would be. So if anyone wants to shed light on that one, please help.
So I've heard arguments from physicists before, saying that the planet near a blackhole in Interstellar would be unstable, or bathed in lethal radiation from the accretion disk, etc. But it just dawned upon me that it should be flat out impossible for it to be there.
Of course, that's calculated from my position of not understanding most of GR, so I might be wrong. (I know, it surprises me too.;)) If anyone knows better, please do correct me.
So for a Schwarzschild kind of black hole, the time dilation effect in relation to a far far away observer is the square root of (1 - 2GM/rc2). So as you get closer to the Schwarzschild radius, that approaches infinity.
Black holes also have a photon sphere, i.e., a radius under which even photons can't maintain a stable orbit. In the recent photo of a black hole, yeah, that was what the black blob in the middle was. It wasn't the event horizon itself.
That radius, again for a Schwarzschild kinda black hole, is 3GM/c2.
Thing is, if you substitute the latter formula into the former, you're still at VERY tame time dilation.
Ok, so at this point I should probably add SR time dilation, since that planet or its star would be orbiting around the star, not hovering in place. And the thing is, we still have some thousands of times worth of time dilation for that to explain. The OVERWHELMING difference in how fast time flows would in fact be from it moving incredibly close to the speed of light, rather than the black hole itself.
I.e., that planet wouldn't be somewhere at the outer edge of the accretion disk. It would be right at the INNER edge of the accretion disk, and at that, quite spaghettified.
So am I wrong there?
Also, obviously I'm not qualified to touch the maths for a ROTATING black hole with a 10 lightyear pole. Which the one in Interstellar probably would be. So if anyone wants to shed light on that one, please help.
via International Skeptics Forum http://bit.ly/2Z8F4Ki
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