Timeline for Event Horizon of Supermassive Black Holes
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
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| Jan 8, 2015 at 16:13 | comment | added | Timaeus | I'm not sure how physical an instantaneous impulse is, I always imagine it as an idealization of a very very short burn, and during your very very short burn you fall farther from the horizon than you climb out, and I use that terminology merely to contrast the radial fall and radial climb contrasting against the tidal forces which are a completely separate issue. My goal is to make that distinction clear without obscuring things with a choice of (an arbitrary) coordinate system. | |
| Jan 8, 2015 at 16:08 | comment | added | Timaeus | Exactly at the event horizon if you can instantly change your velocity to speed c in the direction directly away, then you can escape (the singularity, though not get away). The radial direction being timelike is exactly what I was trying to describe, you fire your rockets as hard as you want, but you end up closer than before. Once you are within the horizon you can fire your rockets and travel for a finite interval (whether an impulse like you suggest or a slower burn) but at the end of your interval you end up closer than you were at the beginning of the interval. | |
| Jan 7, 2015 at 18:38 | comment | added | Hypnosifl | (continued) Whereas in Kruskal-Szekeres coordinates or a Penrose diagram, you can increase the value of your radial coordinate by firing your rockets, the issue in this case is just that your radial velocity outwards is always slower than that of the event horizon, which moves outward at the speed of light in these coordinates. | |
| Jan 7, 2015 at 18:36 | comment | added | Hypnosifl | "But if you want to run away from the black hole, you have to start accelerating away and it takes time for your rockets to start and during that time you fall even closer so now your rockets have more falling to overcome." -- I don't think this explanation really makes sense, the reason you can't increase your radius in Schwarzschild coordinates has nothing to do with the time for your rockets to start (even if your rockets could instantaneously start and cause your proper acceleration to jump discontinuously to a large value, it wouldn't help), it's that the "radial" coordinate is timelike. | |
| Jan 7, 2015 at 17:53 | history | answered | Timaeus | CC BY-SA 3.0 |