If you dig a hole through the earth where will it come out at?

Answer 1

Let's suppose, just for sake of argument that you had a drill capable of plowing below where you are standing right now and grinding its way straight through the middle of the planet to the other side. Where would you end up?

Surf on the Google map below, find where you want to dig your hole and click there. After this, click on "Start Digging..." and you will see the place where you going to end up.

Scientifically speaking it would be impossible to dig a tunnel through to the other side of the world, but it's fun to pretend! If you attempted to dig a hole to the other side of the Earth, you would be digging through:

» More than 12 000 kilometres of solid rock and molten magma

» Rock reaching temperatures up to 6000 ºC and

» Extreme pressures up to 300 million times greater than the pressures we experience on the surface of the Earth!

Also, the Earth is not a perfect sphere. It is slightly flattened at the poles, and bulges a little at the equator due to the Earth's spin. So technically, if you dig a tunnel through to the other side of the globe, you would not come out at the place shown on a Google Map which is an almost perfect sphere.

If you did somehow manage to dig a hole to the other side of the Earth, would you fall through?

Again, theoretically no! The Earth continues to spin as you fall, gravity changes as you fall to the Earth's centre and friction would slow you down. If you ignored all of these factors, scientists think it would take about 42 minutes to fall through the tunnel.

Answer 2

If the hole is not all the way through the earth, the stone will stop when it hits the bottom of the hole.

If the hole is in fact all the way through the earth, and you can see daylight through it at midnight, then it gets interesting.

If you drop a stone into the hole, it never stops. It accelerates (falls faster and faster) until it reaches the center of the earth. If it hasn't melted yet, it then begins to decelerate (move slower and slower), until it just reaches the mouth of the hole on the other side of the earth, where its speed is zero.

If there's nobody there to catch it, it falls back into the hole, and goes through exactly the same experience in reverse, until it just barely emerges from the opening of the hole, at your feet.

Now it's right back where it was when you dropped it. If you don't grab it either, then it starts the whole thing all over again.

You can see that the stone is oscillating like a pendulum, back and forth from one side of the earth to the other, by way of the center of the earth. It has zero speed at the ends, and maximum speed down at the center of the globe.

The period of this pendulum ... the time it takes to reappear at your feet after you drop it in ... is about 86 minutes. It's the same as the minimum orbital period for a satellite ... the period a satellite would have if there were no atmosphere and you could put it into an orbit that just skims the surface of the earth. And it's also the same period that a pendulum would have if it hung from an infinitely-long string and just barely cleared the ground at the center of its swing.

(I used to be able to prove why these 3 periods are all the same 86 minutes, but that was a while ago, like before dirt was invented.)