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| Tags: black, distance, hole |
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#1
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I think I have it now:
Gong back to the *definition* of second and metre we have- "The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom." and "The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second." So as far as the mothership is concerned, letting out pulses at the above time interval corresponds to "one mothership metre". For a hovering reflector near the EH, the time taken for the mothership to receive a particular pulse is long, and the mothership has in the mean time let out loads of pulses. At the time of reception of a particular pulse, there will be loads and loads of "in transit" pulses, all "one mothership metre" apart. So as the reflection point approaches the EH, the measured "mothership distance" approaches infinity! Doh! Also, for an infalling reflection point, the time between pulses received at the motherhsip increases arbitrarily. This means that the object apparently approaches infinite velocity (well, relativistically c acts like an infinite velocity). So in "mothership units", the radial distance to the EH is infinite, and an infalling body speeds up to c. Ho hum. I still have a few more doubts relating to how the (idealised) winch line sees all this, but I'll give it a rest for a few weeks. BR p.s. thanks to JB and TR for taking this seriously. Sane people do contribute! |
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#2
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Dr. Photon wrote: I think I have it now: Gong back to the *definition* of second and metre we have- "The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom." and "The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second." So as far as the mothership is concerned, letting out pulses at the above time interval corresponds to "one mothership metre". At first, yes. But as the mothership accelerates, it measures the distance between pulses differently, due to the relativistic Doppler effect. Pulses going down are a shorter distance apart in its new frame of reference; pulses coming up get longer. For a hovering reflector near the EH, the time taken for the mothership to receive a particular pulse is long, and the mothership has in the mean time let out loads of pulses. At the time of reception of a particular pulse, there will be loads and loads of "in transit" pulses, all "one mothership metre" apart. So as the reflection point approaches the EH, the measured "mothership distance" approaches infinity! No, the distance in the frame of reference in which the mothership is currently at rest does not approach infinity. Just the number of pulses. The pulses near the mirror are at shorter and shorter distances apart. The sum of this infinite number of distances, with successive ones getting smaller and smaller, converges to a finite value. Doh! Also, for an infalling reflection point, the time between pulses received at the motherhsip increases arbitrarily. This means that the object apparently approaches infinite velocity (well, relativistically c acts like an infinite velocity). So in "mothership units", the radial distance to the EH is infinite, and an infalling body speeds up to c. Your latter statement is almost correct, with a little adjustment, although I don't understand your reasoning. In the frame of reference in which the mothership is currently at rest, a falling object will be close to c if it is near the event horizon at that time, using that frame's definition of simultaneity. The velocity we're talking about here is a relative velocity between the the infalling object at the time it's about to be at the horizon and the mothership. If we wait a bit longer on the mothership and then analyze the situation again, from the new frame of reference, we're still condisering the velocity of the infalling object at about the same time as before. It hasn't changed. But we're comparing it to the velocity of the mothership at a later time. During this time, the mothership has accelerated, increasing the relative velocity. This relative velocity increases indefinitely, but never reaches c. Ho hum. I still have a few more doubts relating to how the (idealised) winch line sees all this, but I'll give it a rest for a few weeks. BR p.s. thanks to JB and TR for taking this seriously. Sane people do contribute! |
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