Unanswerable Question?

Question

If you could drill a hole through the centre of the earth and out to the other side, Then drop a stone into the hole (Taking out all obstacles even the heat) what would happen to the stone. Facts only please, I've pondered this for years.

Answer 1

The gravitational centre of the Earth is the exact centre of mass, so that is the point towards which the stone would be pulled. The fact that there was nothing at that point is irrelvant.

So the stone would accelerate toward that centre point, and once it passes it it would then slow down until it stops, then gets pulled back. This to-ing and fro-ing would continue until the stone eventually came to rest in exactly the same way as the weight on the end of a pendulum.

Far from being an Unanswerable Question, it's actually pretty easy, provided you simly think of the gravitational centre of the Earth as the lowest point of the arc through which the pendulum swings.

Answer 2

Assuming that there is no loss of momentum to friction, and that the hole goes from Pole to Pole (so rotation is taken out of the equation), the classic answer to this proposition is that the stone would travel all the way through the Earth. It would accelerate until it reached the center, then begin slowing down as it began rising on the other side. It would rise above the surface on the other side exactly as high as you initially dropped it, then fall back down and repeat the process in the other direction.

This oscillation would continue indefinitely, like a perfect pendulum.

Answer 3

Nigel D has exactly the right answer but a better question to ponder for the next few years might be....

If you could dig a hole with a spade down and down into the earth and then keep going right past the earth's core and keep on digging would you come out feet first?!!!

Answer 4

Assuming the tube is a vaccum the only force acting on the stone would be gravity
Presuming that the amount of gravitational force is evenly spread around the circumference of the tube you drop it down so it falls "straight" it would eventually fall to the center of the earth where it would be evenly pulled up and down and so sit in the middle.
It may osscialate back and forth as the acceleration may cause it to pass the center and then it would gradually be pulled back.

Answer 5

Well, because gravity pulls things towards the centre of Earth, I'd say the stone will fall, but eventually slow down when it's gets to the core.

Answer 6

my guess is it would travel back and forth from one end to the other gradually decreasing distance and eventually stop in the centre of the earth. i dont know if it`s possible to drill through the centre of the earth, but the people who drilled the channel tunnel achieved something similar. perhaps they could try this next.

Answer 7

Assuming the stone didn't hit lava and melt, the stone would still not go all the through. The fact a stone 'falls' to the ground is based on gravity of the earth, which is held in its center by mass and spinning motion. This is all theory though, so I'm just assuming that it would be impossible to have a stone fall 'through the earth'.

Answer 8

I agree with Nigel D, seeing it as a simple model with the earth as a perfect sphere of uniform density.

Answer 9

it would oscillate about, then come to rest at the exact half way point - in other words where the middle of the earth would have been , if you hadn't drilled it away.

Answer 10

gravity would keep it in the centre of the earth