[stana (OP)]

Hey, I was wondering, I grabbed myself a spade, and went in to my back yard and started to dig, all the way through the crust, through the core. What would happen when I came to Australia? (I live in England, and to my knowledge on the other side of the world to me is Australia) Would i spin so i go feet on the floor? Or fall downwards? (upwards to them)?


Also, If i jump at The last minute in a falling lift, would it save me?



P.S I apologize if there are any spelling mistakes on this post, my keyboard isn't cooperating with me. Thanks

[DoctorBeaver]

Australia is a lot nearer the equator than the UK (equivalent to the Sahara desert) so you wouldn't arrive there by going through the centre of the Earth. You would actually come out 550 miles (880 kilometres) southeast of New Zealand at the aptly named Antipodes Islands.

If by some miracle you did manage to travel right through the centre travelling feet first, then that is how you pop out at the other side.

[stana (OP)]

so would i fall? and keep falling into space? or fly up then would the force of the earth pull me back down?

[rosy]

Hmm, well... if you dug into the centre of the earth (I'll ignore the fact you'd be baked to a crisp by the heat of the core and just talk about the gravity), then as you dug into the earth the effect of gravity on you would be less and less (you can show that inside a spherical shell with a uniform mass per unit surface area you don't experience any force due to graity, my dad showed me how to do the maths when I was about 18, but I've forgotten). You can think of any earth outside you as being a series of concentric shells stuck together.
So the force on you in the middle would be nothing.
As you started to dig out from the centre again, you'd essentially be digging upwards toward the earth's crust on the other side of the world.
So you'd tend to fall back down your tunnel toward the middle if you didn't have climbing gear.
If you fell into a hole that went all the way through the earth, there would be an acceleration due to gravity until you got to the earth's centre, when you'd be travelling fastest, then a deceleration due to gravity on the way out the other side. If we now ignore air resistance, you'd find the slowing effect on the way out was such that you came to a stop at the same distance from the centre as you started.. the surface of the earth on the other side. At which point you'd fall back toward the centre and out toward your starting point on the other side.
The principles are actually pretty much the same as for a pendulum which accelerates as it falls toward the earth, decelerates after it passes through the lowest (most stable) point and starts to head up again... and just like a pendulum, if we then include frictional forces (in this case air resistance) the system loses energy and you'd eventually come to rest in the centre of the earth.

[paul.fr]

Stana,

As well as reading the excellent reply by Rosy. These links should answer any other questions you have:

http://www.thenakedscientists.com/forum/index.php?topic=122.0
http://www.thenakedscientists.com/forum/index.php?topic=9457.0
http://www.thenakedscientists.com/forum/index.php?topic=8629.0