
Thank you so much for your answers. School is going great! I will also discuss this with my professors. But just to clear up some confusion that I had, I always believed that time "stopped" on the event horizon (not the singularity), and the singularity was just, as you said, a point of zero dimensions, infinite gravity, density, etc. (Most people think that this is just where relativity and physics in general breaks down, but I don't know enough to talk about that) I have always compared the event horizon to the speed of light, in other words, if you take into account what an outside observer would see if a person fell into a black hole it would be similar to what they would see if a person began approaching the speed of light. If you look at someone who is continually accelerating and approaching c, you would see them get closer and closer to the speed of light but never actually get there (from your point of view), you would also observe their clocks running differently than yours. Now if you look at someone falling into a black hole, you would see much of the same thing: the person who is falling in continually approaches the event horizon, but never actually gets there (from your point of view) you also, like the speed of light example, see their clock run slower than yours. So I have always thought of the event horizon like reaching the speed of light  if you reach the speed of light time "stops" for you relative to the outside observer, and if you reach the event horizon time "stops" for you relative to an outside observer. But what is nice about a black hole is that the person falling in can actually pass the event horizon (never mind the fact that he or she can never get out  this is purely a thought experiment so we do not have to worry about that). Eventually you reach the singularity, but I don't think we can really describe that point in the detail we want with the physics we have. So what happens between the event horizon and the singularity? Where gravity is strong enough to prevent light from escaping but does not yet equal infinity? This is where I might have gone wrong, but I have always thought of this as "exceeding" the speed of light (because you have past the event horizon, which was like the speed of light). Now we all know that for the person falling in, time would pass at a perfectly "normal" rate, but how would he or she see time in the rest of the universe pass (If they even could see the rest of the universe at this point)? Or how would you see their time pass if you could look into the black hole? Would being in a gravitational field that has an escape velocity greater than c but lower than infinity be equal to a velocity greater than c (or would it have the same effects as a velocity greater than c but less than infinity  because we really cant describe infinity)? The whole point of these questions is to try andm understand if time "travel" to the past is even a remote theoretical possibility using this method. Thank you again for your help, it is greatly appreciated!
  Answer 1:
Black holes are asymmetric, from what I can tell. Light is not so much trapped inside of an event horizon, but red shifted into infinity (infinite wavelength, which means zero frequency, and thus zero energy). As an outside observer watches an object falling through the event horizon, the light that is emitted from it will be increasingly red shifted until it can no longer be seen, no longer possessing the energy to stimulate any kind of camera. Now, I think that light does get "delayed" as it comes out from very near the event horizon (not actually beyond it, but very close), so you will if you have an infinitely sensitive camera be able to see the object falling in forever, but if you were to subsequently fall into the hole yourself, you would see something very different from the leftover residual image at the event horizon. I don't understand this  this is well outside of my understanding of physics exactly what happens in a black hole even under Einstein's theory. Supposedly, once through the event horizon, you could see the singularity. Also any light shining on you from the outside will be blue shifted, but the magnitude of the blue shift becomes infinite only as you reach the singularity, or so I understand. Why does the red shift become infinite at the event horizon but not the blue shift? I don't know. I'm not even sure that it does. As for our theories of physics breaking down at the singularity, that's only what quantum mechanics as we understand it says. It could be quantum mechanics that is wrong, not relativity  or, most likely of all, they're both wrong, but in some bizarre way that we've not yet envisioned. The trouble, of course, is this whole thing of cosmic censorship: because you can't see the singularity concealed within the event horizon, you can't collect data on what may be actually happening in there.
Click Here to return to the search form.





Copyright © 2015 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use


