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Black holes are a bit off the original topic, so I'll try to keep this short, but I did want to comment because it contains a couple misconceptions and one extremely interesting question.

werd19 writes:

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But I'm thinking 2 black holes w/ as much matter in them as were talking about would be pretty close to infintely hard.

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The surface of a black hole is actually an event horizon. Information about events inside the black hole cannot escape outward through this horizon, but matter and energy are sucked relentlessly in. Anything impacting a black hole would pass through the event horizon into the interior of the black hole, though relativistic effects make direct observation of that event problematic.

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Black holes are centers of gravity correct? Very strong gravity due to huge amounts of matter in very small volume? So shouldnt they react upon collision as other masses would? in an explosion?

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Immanuel Velikovsky once wrote a book called Worlds in Collision, and I wish someone (a qualified someone) would write a book called Black Holes in Collision, because I think observation of such an event would be extremely revealing scientifically.Imagine two normal, equally sized planets colliding head on, and you happen to be sitting at the point of impact. Just before impact, the net gravitational attraction you would feel would be zero, since each planet is exerting an equal yet opposite pull on you.Now imagine two equally sized black holed colliding head on. At the moment of impact and at the point of impact the net gravity would be zero. The event horizons of the black holes would disappear at that particular point.In reality this would neither be a sudden event nor an event local to the point of contact. As the black holes grew closer their event horizons would melt away and retreat from the area around the point of contact because the net gravity at the region between has an escape velocity less than C. What would happen? Would matter explode outward from this region before the black holes ever contacted one another? Or would the matter inside the black holes shift quickly away from the point of contact and remain within the black holes? Would the net approach velocity of the black holes be a significant factor? Since the holes melt away from the point of contact, how do they ever combine?Anyone know?--Percy

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[This message has been edited by Percipient, 05-22-2002]

Pretty neat stuff, thanks!Do you know of any simulations that show the changes in the position of the event horizons as the black holes near each other? That NCSA webpage reveals that energy formerly within the black holes *does* escape, if I'm interpreting the escaping photon diagram properly, but it would be interesting to see how the event horizons actually change.--Percy

One of the predictions of Einstein's theory of relativity is that gravity is a side effect of the shape of space, and that the shape of space is influenced by mass, and that therefore light, which has no mass, should be influenced by gravity as much as mass.This was verified by Author Eddington in 1919 when he went to Africa to observe a total solar eclipse. He made observations verifying that the path of light from a star whose position lay close to the edge of the sun was bent by the sun's gravity by the predicted amount. Eddington's achievement made headlines at the time. He was knighted and became Sir Arthur Eddington.The opinion today is that Eddington's claim of verifying relativity wasn't justified because the equipment he had available contributed too much error for a definitivie conclusion, but the bending of light by gravity has been verified literally hundreds of times since then to many decimal points of accuracy.--Percy

KingPenguin writes:

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however the rate at which the universe is spreading is gradually slowing down and will eventually come back upon itself and most likely create a big bang when it becomes as compact as is physically possible.

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Scientists a couple years ago were surprised to discover that the rate of expansion of the universe is accelerating. The causes and implications are still being worked out.--Percy