How do inertial frames centered on a black hole's horizon work?

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The discussion revolves around a puzzle regarding inertial frames centered on a black hole's horizon, specifically how two probes launched by an astronaut behave differently when one is above the horizon and the other below it. The astronaut launches the first probe just before crossing the horizon and the second probe immediately after crossing, both at speeds close to light. While it seems that the probes should separate due to their differing positions relative to the horizon, in the astronaut's local inertial frame, they appear to move closer together. This paradox raises questions about simultaneity and the nature of observations within and outside the event horizon, emphasizing that while the infalling observer perceives the probes converging, an outside observer cannot witness the events beyond the horizon. The discussion concludes that the apparent convergence does not imply a physical collision, as the astronaut reaches the singularity before any such event can occur.
  • #91
craigi said:
Your rockets just shift the problem. How heavy is a rocket capable of imparting near infinite impulse?

If it bothers you that much, then assume that the two probes free-fall in with the astronaut but not connected to him in any way. Since free-fall trajectories are independent of the mass of the object, all three objects (the astronaut, the first probe rocket, and the second probe rocket) fall along the same trajectory (at least until each probe's rocket fires to launch it), which is all that's required for the thought experiment.

(Also, there's nothing in the scenario that requires the probes themselves--the payloads of the probe rockets--to be heavy objects. They could be nanotechnology probes made of a few tens of atoms. Then the total mass of each probe rocket could still be much, much smaller than the mass of the astronaut with his life support system, even after allowing for all the rocket fuel necessary to launch the probes at speeds close to that of light.)
 
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  • #92
Several off-topic posts have been removed and the thread closed.
 

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