Blackholes2 Forum Message Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: Event Horizon And Escape Velocity Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by Pranov/">Pranov on February 24, 2000 20:21:46 UTC

: :What mechanism makes it impossible for the particle to escape again?

: Though most people do, I don't like to think of it in terms of escape velocity. The actual mechanism is gravitational time dilation. Once a Scwartzchild hole is stabley formed, and as long as we take the geometry of the space-time to remain static(no mass loss due to Hawking radiation) lets imagine a probe is dropped or in your case(E > 0) thrown into the hole. The time that goes by according to the probe between the time its released and the time it reaches the event horizon is finite. However, according to a clock kept remote from the hole the falling clock is entering extreme gravitational time dilation. According to the remote clock it takes an infinite time before the falling clock reaches the event horizon. Now lets extrapolate the scenario reversed. A clock seen falling out of the hole must have been falling out for an infinite time, or more realistically ever since its creation. Therefor no object will ever be observed emerging from the hole throughout the time that the hole remains static. So it is due to this time dilation that the only times on a remote observer's clock that an object may be observed as emerging from an event horizon is when the geometry of the space-time is not static.

That sounds reasonable...thanks for the answer. I have another question: How will the scenario be from the probes point of view. It passes through the event horizon and gets out through the event horizon (although the rest of the universe might have disappered during the, from the external point of view, infinite time)?

 Web www.astronomy.net