What would happen if you drilled a hole in the Earth so deep that it reached the other side?

Question

Imagine that you could drill a hole into the Earth's surface that is a mile wide. The hole is so deep that it pierces the Earth's molten inner layer and reaches the other side. Then, you drop an object into the hole. What happens to the object?

Answer 1

The Earth is a sphere.  If by get to "the other side", you mean the exit point if a given line passes through the hot molten core of the Earth (center of the sphere), then depending on the angle of the hole the object would pass through the hole and go out the other side.  That is supposing that it is launched correctly and neither burns up or gets stuck in something. However, since drilling through the magma at the core of the Earth and keeping a hole exposed is an impossible task at present, and will be for a long time, it is hard to answer this question thoroughly.

Answer 2

Gravity would keep it from floating off into space on the other side. Someone there might find it and toss it back.

Answer 3

This is a pretty classic problem in an upper level undergraduate mechanics class (see Marion and Thornton Chapter 5), that is if you drill straight down so you go through the center of the Earth.

What happens is all the work done by gravity when you drop it up until it reaches the center is acting to accelerate it towards the "other side."  Once it passes the center, that same gravitational force acts to pull it back.  Without air resistance, the object would oscillate between sides of the earth, provided you dropped it with no initial velocity.  In a more realistic formulation with actual air resistance, it will be losing speed each time it goes back and forth so it will just oscillate a while and then stay at the center.

Answer 4

Well, first of all you cant drill a hole through the earth, because the pressure and heat would melt the drill bit before you got too far. But if you did manage to do it, I think that whatever item you dropped would just be suspended in the hole at the center of the earth because this is where the earth's gravitational pull is the strongest.  

Answer 5

I don't think you could. I think the hole would cave in.  

Answer 6

Whoa!  I started to answer this and it seemed easy.  Then I thought about other forces that would come into play and it became not so easy.  

Some info you might want to add to your question.

Where is the hole placed?  Along the equator, along it's axis or somewhere else.

Answer 7

Well you can't practically drill a hole through the center of the earth because it's just too hot to keep a tunnel drilled or open at the core. But let's pretend you could. We'll also do the common physics simplification of ignoring friction.

When you drop an object into the hole, it will begin falling toward the center of the earth, just like when you drop something on the surface. As the object falls farther the amount of earthen mass above the object becomes larger and starts exerting an "upwards" force on the object. When the object reaches the center of gravity of the earth (near or at the geometric center) there is as much mass "above" it as "below" it so there is no net force acting on the object. I'm using "above" and "below" relative to where you first dropped it.

At the center, the object has no net force acting on it, but it has a substantial velocity (hence momentum) which causes it to continue moving past the center and out toward the other side. As it continues away from the center, there is ever more mass behind it than in front of it; this causes a net force toward the center thus slowing the object. When the object reaches the other end of the hole, it will have lost all it's velocity and then be pulled back through the hole as if you had just dropped it from the far end.

The object will pendulum back and forth through the hole forever, just as a an idealized frictionless pendulum will continue swinging the to the same points forever.