Originally Posted by
Kev Williams
Back in the early '80's a friend gave me a book from the local planetarium titled 'Black Holes and wardped space time". Some above have mentioned 'event horizon' isn't very descriptive. This book explained the event horizon as simply the points in space in which the gravity from a black hole begins tugging at any nearby mass;
Not quite. The event horizon (EH) is the spherical "shell" of points at which the escape velocity of the black hole is equal to the speed of light. Once an object sails beyond that 'horizon', it's 'event' can no longer be observed. But a black hole can begin tugging on another object far outside of its EH.
Imagine if the Sun suddenly turned into a black hole. Not that it could...it doesn't have enough mass. But if it could and did, we'd sure notice the lack of sunlight but Earth's orbit would remain unchanged. The new black hole would have the same mass as the old Sun and it would tug on Earth with the same strength at that distance. Even Mercury wouldn't notice a change in orbit being that far away from an event horizon that's only 6 kilometers (~3¾ miles) in diameter. But things do get very hairy when you stray very close to an EH. Google "spaghettification" sometime, if you're of a mind to.
Originally Posted by
Mel Fulks
Can a black hole be filled in ? Or would it remain a junk magnet regardless of how much it's already consumed?
P.S. I have tried to write in layman' terms for those who's TV watching is less scientifically inclined .
No, the analogy of it being a hole breaks down completely in that regard. Adding stuff to it just makes it a bigger 'hole.' The increase is usually very small...infinitesimal, even...compared to the total mass. Unless you happen to throw something big at it. Like another black hole. In related news, you may have heard about the first detection of gravitational waves a few years ago. Those waves were the result of two black holes merging into a bigger one.
On the other hand, a black hole can evaporate. It just takes a really, really long time.
Brett
Peters Creek, Alaska
Man is a tool-using animal. Nowhere do you find him without tools; without tools he is nothing, with tools he is all. — Thomas Carlyle (1795-1881)