| Science Forum Index » Physics Forum » Seeing Inside the Event Horizon of a Black Hole |
|
Page 1 of 1 |
|
| Author |
Message |
| Michael J. Strickland |
 Posted: Thu Feb 10, 2005 2:39 pm |
|
|
|
Guest
|
If you are close enough to a black hole, can't you see inside the event horizon?
A particle or photon leaving the black hole from inside the event horizon needs v > c to escape (reach r = infinity), but won't it be able to move out to any r < infinity?.
Therefore, as you move toward a black hole, you should be able to "see" further and further inside the event horizon as your gravitational potential energy decreases so that objects further and further inside the event horizon, moving at v < c, can reach you.
Or (from a GR perspective?), the light which is red-shifted to f=0, originates further and further inside the event horizon as you get close to the black hole.
--
---------------------------------------------------------------
Michael J. Strickland
Quality Services qualityser@att.net
703-560-7380
--------------------------------------------------------------- |
|
|
| Back to top |
|
|
|
| Guest |
| Posted: Thu Feb 10, 2005 2:39 pm |
|
|
|
|
Michael J. Strickland <qualityser@worldnet.att.net> wrote:
[quote:500eb1e41b]If you are close enough to a black hole, can't you see inside
the event horizon?
A particle or photon leaving the black hole from inside the
event horizon needs v > c to escape (reach r = infinity), but
won't it be able to move out to any r < infinity?.
[/quote:500eb1e41b]
This is why the Newtonian picture of a black hole as a star with
escape velocity c shouldn't be taught (or should be taught only
with *very* strong disclaimers).
In Newtonian gravity, you would be right. In general relativity,
you're not; light cannot move beyond the event horizon of a black
hole at all. One way to look at this is to think of the event
horizon as expanding at the speed of light. The curvature of
spacetime near the event horizon happens to be high enough that
even though it's expanding at the speed of light, its area does
not increase -- not an intuitive idea, but that's how it works
out. The upshot is that a general relativistic black hole is
*very* different from a Newtonian one.
Let me recommend Kip Thorne's book, _Black Holes and Time Warps_,
for a very nice nontechnical introduction to black holes in
general relativity.
Steve Carlip |
|
|
| Back to top |
|
|
|
| CWatters |
| Posted: Thu Feb 10, 2005 4:08 pm |
|
|
|
Guest
|
"Michael J. Strickland" <qualityser@worldnet.att.net> wrote in message
news:sLOOd.187095$w62.169123@bgtnsc05-news.ops.worldnet.att.net...
[quote:856690c878]If you are close enough to a black hole, can't you see
inside the event horizon?
A particle or photon leaving the black hole from inside
the event horizon needs v > c to escape (reach r = infinity),
but won't it be able to move out to any r < infinity?.
[/quote:856690c878]
I thought the definition of the event horizon was the point at which you
need to travel > c to increase r. So to achieve r> event horizon you need to
travel >C which isn't possible. |
|
|
| Back to top |
|
|
|
| Sam Wormley |
| Posted: Thu Feb 10, 2005 4:12 pm |
|
|
|
Guest
|
Michael J. Strickland wrote:
[quote:1be622ac1d]If you are close enough to a black hole, can't you see inside the event
horizon?
[/quote:1be622ac1d]
No, the space-time curvature is so strong that light can't travel
toward your eyes... you won't care anyway. |
|
|
| Back to top |
|
|
|
| Uncle Al |
| Posted: Thu Feb 10, 2005 4:15 pm |
|
|
|
Guest
|
[quote:c648cf3f5d]"Michael J. Strickland" wrote:
If you are close enough to a black hole, can't you see inside the
event horizon?
[/quote:c648cf3f5d]
No, by trivial definition. You don't "look in" to image, git, you see
photons that are coming out. But no internal photons escape a black
hole's event horizon.
[snip maunder]
New idiot on board.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf |
|
|
| Back to top |
|
|
|
| Michael J. Strickland |
| Posted: Fri Feb 11, 2005 1:07 pm |
|
|
|
Guest
|
--
---------------------------------------------------------------
Michael J. Strickland
Quality Services qualityser@att.net
703-560-7380
---------------------------------------------------------------
"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:73QOd.8524$qH7.472176@phobos.telenet-ops.be...
[quote:b9bc41c3d3]
"Michael J. Strickland" <qualityser@worldnet.att.net> wrote in message
news:sLOOd.187095$w62.169123@bgtnsc05-news.ops.worldnet.att.net...
If you are close enough to a black hole, can't you see
inside the event horizon?
A particle or photon leaving the black hole from inside
the event horizon needs v > c to escape (reach r = infinity),
but won't it be able to move out to any r < infinity?.
I thought the definition of the event horizon was the point at which you
need to travel > c to increase r. So to achieve r> event horizon you need
to
travel >C which isn't possible.
[/quote:b9bc41c3d3]
I think the definition of the event horizon is:
That distance at which escape velocity from the black hole is c. |
|
|
| Back to top |
|
|
|
|
