Journey to the centre of the Earth.

Originally posted by WoodPush
Even in a vacuum, you'd eventually settle in the core.

You'd keep smacking into the hole's walls, as the earth would keep rotating, and you of course wouldn't along with it. You'd eventually lose enough energy to end up in the core, regardless.

Well I was assuming magnetic levitation to keep you frictionlessly centred.

http://en.wikipedia.org/wiki/Gravity_train

Originally posted by amolv06
The centripetal force of gravity. Angular momentum would have to be conserved, right?

No gravity is pulling you strait down towards the core at all times. (assuming earth is a perfect
sphere of uniform density).

Angular momentum does have to be conserved and that is the problem.

To change your angular momentum you need a force perpendicular to the force of gravity to
reduce your angular momentum as you descend towards the core and then increase it back
up (in the opposite direction as you came out the other side).

Aha! So as you fell to the center of the earth your angular velocity would increase since your moment of inertia decreases. I had missed that.

However, if your hole were drilled through the access of rotation this would not be an issue, correct?

Originally posted by amolv06
Aha! So as you fell to the center of the earth your angular velocity would increase since your moment of inertia decreases. I had missed that.

However, if your hole were drilled through the access of rotation this would not be an issue, correct?

Indeed if you drilled a hole strait through the earth on the Earth's rotational axis you would
not have any trouble with angular momentum...

If the earth were a perfectly sphere of uniform density that didn't wobble on it's axis.


On a side note...

While this is evidently not a practical option on the earth with it's hot liquid core, It might
be a practical option on much smaller rocky bodies (large asteroids or small moons).

You would still want to use magnetic levitation to reduce friction and deal with any angular
momentum and non-uniform density issues.

Originally posted by googlefudge
Indeed if you drilled a hole strait through the earth on the Earth's rotational axis you would
not have any trouble with angular momentum...

If the earth were a perfectly sphere of uniform density that didn't wobble on it's axis.


On a side note...

While this is evidently not a practical option on the earth with it's hot liquid core, It might ...[text shortened]... tion to reduce friction and deal with any angular
momentum and non-uniform density issues.

Seems like a lot of bother just to keep falling down a hole.

Originally posted by kevcvs57
Seems like a lot of bother just to keep falling down a hole.

It's actually a rather fast and energy efficient method of travel (once you have successfully
drilled you vacuum evacuated tunnel and installed the guide magnets).

Whether or not it's a practical method of travel depends on the difficulty of digging the
tunnel and keeping it open (again much easier on a large asteroid or small moon (or planetoid).