I have always wonderred this and no-one can tell me what would happen (clearly because it is impossible). It is a good topic though.
OK
Lets ASSUME you could bore a 1 metre diameter hole right through the centre of the earth, North Pole to South Pole. You then get a ball and drop it in. What happens to the ball when it gets to the centre of the earth? Bearing in mind that our hole is thermally protected all the way through.
In addition, would gravity be affected.

[ January 06, 2004, 02:25 PM: Message edited by: Sigmeister ]

Eventually the ball would come to rest in the center of the hole, (and the earth). Before it comes to a stop, it would act like a yoyo. It would fall into the hole, then go past the center of the earth, then start to slow down, then reverse direction, etc. If there were no wind resistance, dust particals, etc, the ball would continue in this fashion indefinately until something caused it to stop travelling in its undisterbed state. It would take the ball quite a long time to come to rest in the center. The only thing slowing it down is the loss of energy through resistance in the wind and dust.

If the ball was magnetic though, it would be shot out the end of the hole and into space because the magnetic field travels in one direction through the center of the earth and in the opposite direction on the outside of the earth. Thats if you disregard the magnetic force in the center of the earth. It is quite possible that a magentic or metalic ball would go straight to the center of the earth and stay there.



[ January 06, 2004, 02:42 PM: Message edited by: Courtancer ]

i reckon the hole would get filled up
who says its solid ur digging thru

[ January 06, 2004, 04:56 PM: Message edited by: Nav2k ]

Yeah I reckon it'd stay in the middle.

I agree but in the case of a magnetic ball there are variables such as the orietation of the poles of the dropped object making it difficult to predict.

I agree with the others who say that it would stop in the middle...

I think i would like to nominate myself to jump into this hole too, sounds like fun

If the speed at in which you fell was great enough you MAY exit the atmosphere.

Either way, its going to be crused in the center when it stops.

Theory is good until put into practice.

Lets try it!

i reckon the ball would get replaced by a new one cos u were silly and dropped it into a hole

Would the pressure increase as you got closer to the centre of the earth? Or does this only happen of you have something pushing on it (water, earth)? If so, does this mean if DrEvil jumped in and fell to the middle, would he be crushed into a singularity? Hmmm.......
Also if we assume there is no friction, you would be accelerating the whole way to the centre then as you passed through you would be decelerating. If the distance to the centre was the same I don't see how you could get shot into the atmosphere. However if you did, it would be a cheap way to launch rockets
If we assume friction is present, does this mean the ball will reach terminal velocity, hit the centre and just stop dead?

Yes. The pressure would increase as you got closer. And there is something pushing on it. Gravity and air pressure, (which put pressure on things just the same as water and earth).

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Also if we assume there is no friction, you would be accelerating the whole way to the centre then as you passed through you would be decelerating.

That is correct.

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If the distance to the centre was the same I don't see how you could get shot into the atmosphere.

This will only happen if you take into account the earth's magnetic field and the metalic ball is dropped in the same direction as the field. Sort of like dropping a tennis ball down a water slide.

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If we assume friction is present, does this mean the ball will reach terminal velocity, hit the centre and just stop dead?

No. If friction is present, the ball will keep travelling from side to side but it would slightly less each time it oscilates until eventually it would stop.