2006-07-05 07:44:22 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Physics
It is the distance at which the escape velocity is the speed of light. Escape velocity from the surface of the Earth is 25,000 MPH, but escape velocity from 4,000 miles above the surface is only 6,250 MPH because gravity gets weaker as the square of the distance. For gravity calculations all the Earth's mass can be considered as at the center of the Earth, which is 4,000 miles below the surface, so at the surface you are already 4,000 miles away, and at 4,000 miles up you are 8,000 miles away, twice as far, so gravity is a quarter as strong. If you compressed the Earth so that it had half the diameter, then the surface would be only 2,000 miles from the center and the escape velocity at the new surface would be four times as much, or 100,000 MPH, but from the location of the old surface, 4,000 miles from the center, which would now be 2,000 miles above the smaller Earth's surface, it would still be 25,000 MPH. The point is, if you compress the Earth enough, it is possible to get close enough for the escape velocity to be equal to the speed of light. Then you would have a black hole.
BTW, you cannot get the same effect by just digging a hole to get near the center, because then part of the Earth's mass would be above you pulling up instead of down, so gravity in a hole actually gets weaker, not stronger. You need to compress all the mass into a smaller volume to make a black hole.
2006-07-05 08:41:05 · answer #1 · answered by campbelp2002 7 · 1⤊ 0⤋
It's the invisible 'point of no return' where anything that drifts inside can never come out, not even light.
The event horizon is a sphere around the hole where gravity is too strong to get away from. The black hole itself is a singularity at the center of the sphere.
2006-07-05 07:50:07 · answer #2 · answered by fresh2 4 · 0⤊ 0⤋
the event horizon i believe it the edge of the black hole where things begin to spin toward the center and get sucked in. its at the point where light cannot escape and things are spinning so fast that if u were able to stand there and survive you would be looking at yourself from behind. at least thats what i learned in school.
2006-07-05 07:48:44 · answer #3 · answered by A T 1 · 0⤊ 0⤋
the event horizon is the distance away from the hole that there is no escape for the mass of what you are in. basically you crossed the line and are getting sucked in
2006-07-05 07:49:49 · answer #4 · answered by ML 5 · 0⤊ 0⤋
I thought it was a theoretical distance from the center of the black hole, when a light particle (or whatever) has a 50 % of either being sucked in or escaping.
Any other ideas or clarications??
2006-07-05 07:47:08 · answer #5 · answered by MK6 7 · 0⤊ 0⤋
It is the distance from the center of the singularity that, once crossed, a photon cannot escape the gravity of the singularity.
2006-07-05 07:50:53 · answer #6 · answered by bequalming 5 · 0⤊ 0⤋
huh?
2006-07-05 07:48:00 · answer #7 · answered by Lawlrus 2 · 0⤊ 0⤋