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# What would happen to Earth if a hole was drilled through it?

Launcher Erik Montes United States
Status Closed Closed 3 years, 6 months ago
Bounty Reward
10

### Labels

Earth sciences the Earth

### Description

I'm interested in knowing what would possibly happen if a hole was drilled directly through Earth entering the North Pole and exiting through the South Pole?

Additionally a related question is, what would happen if once a hole was drilled and water was poured through it, would the water come out through the other end? Or how would gravity have an effect on? Will the water just go through it half way until a gravity equilibrium point is reached?

I know drilling a hole all the way through it is pretty much impossible, but I would like you to pretend it was possible. And go from there. Any information will be great.

I will award 10 credits to the answer that makes the most sense. Thanks!

• Jul 28, 2011

Olavur's answer is right, for an idealized situation (for example, a vacuum [no air resistance] in the hole, no friction with walls of the hole). The interesting thing is that the period of oscillation is fixed (can't quite remember what, maybe 1 hr 40 min). Also, the water, falling under gravity, would try to shape itself into a sphere (due to surface tension). Any object, say a cricket ball, would also oscillate at the same rate. Similarly, suppose you drilled a completely straight tunnel, say from Perth to Beijing, and equipped it with friction-less rails (maglev would approximate this), and there was no air resistance. A rail trolley given a nudge in Perth would roll downwards for half the journey, and use its momentum to run upwards to Beijing. The trolley would appear in Beijing having lost all its momentum. If it wasn't stopped, it would then roll back down the tunnel and reappear in Perth, and so on for ever. Its period of oscillation would be the same as in the hole through the centre of the Earth. Apart from the hole collapsing, the temperature at the centre of the Earth is believed to be about 3000 deg C. This would not be good for a sphere of water!

• Jul 26, 2011

If you dropped an object into the hole, it would follow a simple harmonic motion. Gravity would act as a restoring force, that would always be directed toward the center of the earth. What that means, is that it would oscillate "up and down" endlessly, like a spring.

Of course, the earth isn't a perfect sphere, and the tunnel would most definitely collapse, so this solution is extremely idealized, and not very probable. =)

### Clarifications

Q:

Are we assuming that during drilling, the hole is lined with some kind of casing that can withstand the immense pressure and temperature at depth? There's essentially air flowing from one side of the earth to the other in this hole?

Asked by benedict on Jul 27, 2011

A:

Yes, you can assume that. Basically, getting the hole drilled is not at question. You must assume, that there's a hole already, doesn't matter how it was done. The question is if you dropped an object through what end, would it come out through the other end?

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