Fun Facts

The what if in this is very difficult because gravity doesn’t pull you towards the center of the earth, rather it pulls you towards its mass. So if you made a hole that went perfectly through the center of the earth, and ignoring that the earth isn’t a perfect sphere, then as you approach the center of earth via your tunnel then you have equal amounts of the earth in every direction. You would feel the same amount of gravity but rather than all of it pulling you down, you’d feel the pull in all directions. The lucky thing for you is that you are already traveling at terminal velocity at this point, this assumes the tunnel was not constructed in a manner to allow a vacuum environment, so you’ll pass through the center of the earth without getting stuck. As you begin to rise up the other side of the tunnel gravity from the section of the planet above you will continue to pull you forward, but more and more of the planet is behind you trying to pull you towards it, slowing you down. Chances are that you would not have enough velocity moving forward to get to the end of the tunnel, and you would stop moving toward the end and begin to fall toward the end of tunnel from which you entered. Of couse since you didn’t have enough force to get through the whole tunnel you are not going to have enough force to make it back to where you entered from, so you become a human yo-yo until you finally come a stop at the center of the tunnel in the center of the earth held in the middle by equal parts of the earth’s mass pulling you in every direction equally. You are a puppet but without the strings. Now assuming the tunnel is constructed in such a manner to allow a vacuum environment inside the tunnel you wouldn’t hit terminal velocity and your chances of getting to the other side successfully increase significantly. Or those are my thoughts on the subject anyways.

This is a well-known mathematical problem, and I’m afraid that you’ve got the wrong answer. The key thing to know is that a point inside a spherical shell experiences no force at all due to the gravitational attraction of the shell. How does this apply to your problem? A sphere can be thought of as a whole lot of concentric spherical shells all inside each other, kind of like a pea inside a hazel nut inside a walnut inside a tennis ball inside a softball inside a basket ball inside a … you get the idea. When you stand on the earth’s surface you experience gravity due to all the “shells” that make up the earth. When you are at the centre of the earth, you experience no gravity due to the earth at all, because you are inside all the shells. When you are part way to the centre, you experience a fraction of the gravity at the surface. In fact, the force you experience due to gravity is proportional to the distance from the earth’s centre. These are exactly the conditions needed for “simple harmonic motion”, which is the same sort of motion as a pendulum. And that’s exactly what would happen if you jumped into that hole. You would fall faster and faster as you approached the centre, and as you passed it you would begin slowing down, until you reached a speed of zero at the surface on the other side. You could step off there, but if you didn’t you would begin to fall back again. The journey each way would take about 42 minutes. What’s even more interesting is that the journey time is the same for any straight tunnel through the earth, even if it doesn’t go through the earth’s centre.

@Chris

Stumblerz is not entirely wrong, the post was more of a fun view of the whole paradox.

Here is what I have to say —

Ask yourself what happens when a child plays on a swing (just sitting on the swing after getting it going high, not pumping). Gravity is obviously the force involved in both cases. Gravity pulls toward the center of the earth. The swing picks up speed while it is falling towards the center (the force due to gravity INCREASES the kinetic energy) but once it passes the bottom the kinetic energy keeps it moving and it starts to move away from the center of the earth. Now the force
due to gravity DECREASES the kinetic energy. The child then reaches the top of the swing’s arc (all of the kinetic energy is gone — converted to potential energy due to height) and starts to fall back again.
Hope this helps.

the object you drop will yo-yo back and forth on both sides of the center of the earth,
until all the kinetic energy is gone, and the object will then be suspended at the center. (Of course, since the center of the earth
is molten, this is a completely academic question, but interesting to think about anyway…)

here is another possible answer -

Theoretically, the object would stop at the center of the Earth since everything “falls” towards that point. It is the point at which objects are attracted, so the thing you drop could get not past that point. Of course, it depends on the speed you drop/throw it.

I doubt the person will go anywhere after he hits the center but that’s me.

What if a person goes at speed of light, will he end up on the other side or still get stuck at center?

@Lucky – If someone was traveling at the speed of light when they entered the hole then their momentum would carry them back out the other side and continue going. Now, if you took a mass that was big enough and did the same thing it would result in the same outcome as jumping in the hole on Earth.
The closer you get to the the center of any object the less it’s gravity affects you. Take the moon for example. You are on the surface of the moon. It affects you much less than being on the surface of the Earth. When you are the same distance to the center of the Earth as you are to the center of the moon (If the density/mass was equal) then you would have exactly the same gravitational force being applied to your body regardless of your initial speed. (i.e. Jump up with little effort then jump up with a lot of effort. You will rise off the ground more with the most effort, but gravity is still affecting you the same.
Anyway, a couple of the previous comments were “point on”. If everything was perfect then you would have a yo-yo or pendulum effect. Just because you are going through the center of the object wouldn’t change the end results. You’d end up stopping in the middle just like swinging. You end up at the middle of your swing arc.
Merry Christmas!

you are all $%$%%$, with one or two exceptions! the simple harmonic motion is the correct solution. that, of course, is neglecting wind resistance. and for the gentleman who said that the transit time is the same for any tunnel, even those that don’t transit the core . . . you couldn’t make it through a tunnel that didn’t go through the core, because the earth’s center would attract you and make you hit the inside wall.

why is this a question? have none of you taken 10th grade physics?

Fixed by Stumblerz -

I have fixed your comment, you need manners and respect. Next time you call someone retarded, look at yourself in a mirror and try to distinguish what gives you the right to call someone retarded and what is the difference between yourself and a retarded. I must say you are still young.

i love her

Has anyone speculated about how the answer to this question might differ with other planets in our solar system? In particular, Neptune and Uranus. Those planets have more gravity but their atmospheres are much thinner and they have relatively small solid cores. If the tunnel extends through their atmospheres, and not just through the solid parts, I would think that an object falling down such a tunnel could attain a very high velocity.

By the way, before anyone decides to make this joke on their own, I am aware of the fact that a transvestite theater group called the Coquettes performed a musical titled “Journey to the Center of Uranus”.

it would be impossible even if you met antigravity protocal because of the extreme temperatures. man or machine would disentigrate in the unnatural heat.

@rachella
Force field tube. Where is your suspension of disbelief?

laid off guy… excellent question… and disturbing side note…