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?
you'd be burned to death from molten rock in centre.
if that wasn't there, you'd shoot through the centre, back towards the edge, slow down, then go back, eventually stopping in the middle and have a very long climb back out.
If there was also no air resistance, you'd exactly reach the other side every time and never stop.
Zacmaster. Clearly it depends on where you dig the hole. As the world is largely spherical it doesn't actually matter where you start in order to pass through the centre, so why bother to travel to the south pole!
Which starting point to choose is significant because the rotation of the earth and you with it at the outset would have to be taken into account. NubMaster chose the poles so as not to hit the sides of his hole due to the sideways vector of his starting point/velocity. Ignoring the "wobble" of the earth's axis, he would simply rotate while falling from pole to pole - in theory without dragging against the sides anywhere along his bungee type oscillation from end to end of the axis.