what would happen if there was a hole threw the earth from pole to pole and u tryed to jump threw.............

Question

If there's a hole straight through the earth, from the south pole to the north pole, and you jump through it what would happen? would you keep falling forever, or fall back down when you get to the middle, or is it physically impossible?

Answer 1

Okay, let's assume that the hole is protected from the heat of the Earth's core somehow.

You jump in at the north pole, and you begin falling/accelerating toward the center of the earth.

If the hole is filled with air, you'll eventually reach terminal velocity and stay at that speed until you cross through the center of the earth.

Then you'll begin slowing down and start being pulled in the opposite direction. You'll oscillate back and forth, heading towards the North Pole and then the South Pole for a while, gradually slowing down because of air resistance. Finally, you'd end up motionless at the center of the Earth.

If the tube was a perfect vacuum, with no air resistance, you would jump in at the north pole, and fall down toward the center of the Earth, continually accelerating.

Once you cross through the center of the earth you'd begin decelerating heading toward the south pole. Your velocity would be zero, just as you reached the surface of the south pole. Then you'd start falling toward the center of the Earth again, eventually winding up at the surface of the north pole. Back and forth, forever.

Answer 2

As dbucciar noted, if it were possible to travel in a vacuum, you'd pass right through the earth to the other side, then back again to your starting point, and osscilate between the two. By the time you reached the centre of the earth, falling all that way without resistance, you'd be travelling very fast, and the whole journey to the other side would only take an hour or so.

However, the hole wouldn't have to pass through the centre of the earth, to achieve this effect. If you bored a hole tangentially through the earth (say, from London to New York), and were able to travel along that tunnel in a vacuum, the effect would be the same, and the journey would only take an hour or so, with no expense of energy (the earth's gravitational field would be driving you). Travel from London to New York in an hour, for nothing!
There is a book by Amit Goswami called Cosmic Dancers, that explores this and other interesting theoretical science fiction possibilities.

Answer 3

dbucciar is right if the tunnel is a vacuum, though I think there would surely be some friction in the system somewhere (eddy currents in your body for example). If so you'd not quite reach the surface the other side -- the oscillation would gradually damp down.

However if the tunnel was full of air, it would not work the same.

When you get near the centre, the mass of the earth is all around you. At the exact centre the earth is pulling you out in all directions equally, and so there is no directional "gravity" as such (how would it "know" which way to pull?). This is actually the same situation as in "outer space" -- the enormously vast mass of the universe pulls equally from all directions, cancelling itself out.

If your thought experiment was done in a vacuum, the lack of air resistance would let your momentum carry you through the low-gravity zone, and you would oscillate.

However, if there was normal air resistance, your terminal velocity would decrease as you got deeper (because the directional gravitational pull is decreasing), and by the time you reached the centre you'd be drifting very slowly indeed, and would drift to a stop without oscillating. It would take years, or perhaps centuries.

There would not be normal air resistance though, because the air in the tunnel would all pile up towards the centre, and its density and resistance would be much greater lower down. By the time you got to the middle, there'd be thousands of miles of air stacked up on top of you instead of the usual fifteen or twenty miles, and the pressure would be immense (I think the air would even become liquified). So you'd be crushed by the pressure long before you got there, then your remains would sink untidily into liquid air.

Even if the air remained a gas, it would get denser, and at some point it would be denser than your mangled remains. You are largely solid and liquid, and thus incompressible, so at this point you'd actually float, and never reach the centre at all. If the air was liquid, you'd definitely float, as that's a good bit denser than water (around 1.1 kg/l) and must be somewhat denser than your body too. Bits of your teeth might make it, especially if you've got lots of fillings... Not sure what kind of solvent liquid air is -- some of you might dissolve in it.

Good choice to have a tunnel through the axis of the earth from pole to pole, not elsewhere. If you tried to do it from one side to the other, say at the equator, the coriolis forces would make you hit the sides of a straight tunnel very soon -- you'd be turning faster than the earth. You'd need a tunnel with a spirally curved shape to match your trajectory exactly as the earth turned. I think in the vacuum case you'd orbit about the centre in a distorted eliptical shape, rather than going through it. Possibly your trajectory might even be chaotic.

I wonder how long the pole-to-pole oscillation would take? And I wonder what the pressure of an air column that deep would be, and how much air it would take to fill it?

Edit - Andrew G's idea of tangental travel would work -- but not by simple falling. A tangental tunnel is at a slant to the direction of the earth's gravity, so if you fell down it, you'd immediately hit the side. To get along it, you'd have to slide along the side, on a rail, or perhaps magnetically suspended. The friction would have to be very low indeed or you'd find yourself having to climb back out of a very deep well... You'd also have to contend with coriolis forces, as above.

PS -- Andrew -- does that calculation of only an hour of falling in the vertical case take into account the reduced gravity as you get nearer the centre?

Answer 4

It depends quite a lot on your sence of fantasy: what is this tunnel filled with. generally, you'll keep on falling getting closer to terminal speed(about 200km/h for a human in the atmosphere) until you get to the center. When you pass it you'll start slowing down and at one moment you'll stop moving and start moving back. And so on for somw time until you get stuck in the center of the gravity

Answer 5

You'll be stuck at the center of the earth

Answer 6

The earth's gravity is theoritically at the centre ,so you would be stuck at the centre.

Answer 7

I bet you could get to the other side successfully.

Answer 8

You'd burst into flames before you got half way.

Answer 9

it's hot there! wouldn't like to try burn myself just for the heck of it :o))

Answer 10

You would be a 'kebab" at the other end.