LOL, how did my discussion about the tube in the earth turn into a discussion about blackholes…hmmmm…

Yes and no. What do you mean by that?

kasuo wrote (and everyone just let it slide):

Which is not true. Assuming a frictionless system, the rock would come flying out the other side of the hole at nearly the velocity that you threw it into the hole. The rock would then fall back into the hole, pass through the Earth’s center, and come back out the other side and rise to a height that would be nearly the same as if you’d thrown the rock up in the first place. This “cosmic pendulum” as Cecil called it would continue indefinitely.

Of course, we might have trouble creating a frictionless system and the maximum velocity of the rock would be a function of friction with the air in the hole and the rock would not build up enough velocity to come out the other side. The rock would undergo hysteresis and would pendulum back and forth at ever decreasing distances from the center of the Earth until it finally came to rest at the center.

Of course, this and the other tangental discussions ignore the fact that while the gravitational forces from the ‘hole’ are not present, the gravitational forces from the sides of the hole are still there. If the rock were a perfect sphere and it and the Earth had an even density and the rock was dropped in the exact center of the hole, it might behave as suggested. However, the slightest imperfection or bias from center and the rock will be pulled to the side of the hole where it will tend to stay, though it may bounce down the hole towards the center like it would on an inclined plane…

Blitz, it’s purely a theoretical question with no way to prove the answer. We could talk about it for years [as they already have].

At my college, UCSD, there was a "black hole astronomy society’. They called it the black hole society. Until a few months later when they added a note to their posters that it was an astronomical society as some people got another idea.


[cynical answer]
Human nature. Rather than just say “I don’t know” most humans will change the subject so they can keep talking…
[/cynical answer]
[official answer]
I don’t know…
[/official answer]