Quote:
Originally Posted by xelasnave
If nothing can escape from a black hole how can a black hole communicate its message of gravity to inform the rest of the Universe that it is there?  .
alex  |
Well, thats another question... The Event Horizon is the point at which nothing can leave the black hole, but what happens outside is more visible.
The Gravitational field is similar to any massive object in that it influences what is around it. Anything approaching will have its course altered by the pull of the black hole for example.
However, these nasties also exist in binary systems and they tend to canibalise the other party by sucking off, (In this instance Alex, "gravity does suck"
), huge amounts of gas from the companion star. As the gas spirals toward the event horizon, it gets hotter than hell and emits lots of stuff like radio and X-Rays, that can be detected.
The accretion disk around the black hole will often suddenly flare resulting in a Nova, which can also be observed. Finally, a star ripping around something massive, at awful speeds, that can't be seen is a good indicator of a beastie being present.
Fun stuff. Lots of theoretical examples of how we could use Black Holes to time travel, generate energy etc. Other theories suggest they my be entrances to worm holes but I doubt it. Still others suggest black holes may naturally "evaporate". The physics around them is very poorly understood from what I gather, but we do know they are out there. Nice bed time story for the littlies huh?
