What would happen in theory if we were able to tunnel a hole through the center of the earth and out the other side (of course its not possible in modern physics due to the molten magma core but in theory anythings possible) So what would happen if you threw a pebble down the tunnel? Would it keep being flung out one end and back down the other? Or would it stop in the center and oscilate? Perhaps it would be crushed by the earths gravity at its center. But what would REALLY happen?

It would hit a maximum speed somewhere in the neighborhood of 100-150 mph due to air resistance. Of course that speed will be much slower near the center because the air would be very thick. Practicaly souplike. For a little while it would ocilate from one side of the center of the earth to the other, but eventualy air resistance would stop it.

This is nowhere near possible since whats causing the gravity thing is one big metal ball.

It would stop somewhere in the middle and disingrate. And anyway it would have fried way before having made half the way.

This was discussed by in a book i read part of... Alice, in alice wonderland makes a joke about falling though the center of the earth.. then all the people would be upside down she says! This joke if you don't know is related to the meeting of minds where political from differant time periods figures discuss current problems. One of the things they discussed was simply the exact question your asking. They agreed with the following concept: The man would fall from one end of the earth and fall through the center of the earth until a certain point where earths gravity would reverse and he would go the other way. He would start to slow down and *eventually* be stuck in the EXACT center of the earth.

the pebble will fall towards the center of the earth, increasing it�s speed, may or may not reach a certain terminal speed and pass the center. Once it pass the center, it will go toward the other end of the tunnel, decreasing it�s speed, may pass the tunnel opening if it�s speed (at the center at the earth) is high enough, but will never escape completely due to it�s decerasing speed. Eventually the speed will be zero, and it will fall back through the tunnel and the process repeated again, and every time this happen, the speed will keep decerasing for each �oscillating� due to internal energy loss (cannot remember the right term, just like satellite orbiting the earth, someday it will fall due to energy loss internally) and eventually the pebble will stuck there right in the center of the earth after all it�s kinetic and potential energy is lost.

How old are you guys? In my country, we learn this at 16. it�s all about conservation of energy. Potential to kinetics to potential to kenetics to potential to.....

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Originally posted by Kia Kordestani:
What would happen in theory if we were able to tunnel a hole through the center of the earth and out the other side (of course its not possible in modern physics due to the molten magma core but in theory anythings possible) So what would happen if you threw a pebble down the tunnel? Would it keep being flung out one end and back down the other? Or would it stop in the center and oscilate? Perhaps it would be crushed by the earths gravity at its center. But what would REALLY happen?

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I believe then that the earth would be pulled towards you. Once in the center, the pepple would stop and .... but wait, if this was ... I believe that the pebble would be stuck in the center forever.

But wait. If the pebble was dropped closer to one of the sides of the hole wouldn't it eventually end up being pulled to that side because it is closer to mass on that side? The attraction would be that little bit greater.
Its like this thought experiment. An earth sized sphere with lots of mass. In the center the pull from all sides would be equal so you stay one point. Move just a little out of center and you'll be pulled to the surface.

if they hole was a vacuum your ass would just keep falling from the "top" to the bottom" for ever and fuckingever! simple harmonic motion KEEYAAAA

but since we have air in the tunnel drag would slow your ass down until you were in the center. this is a text book damped harmonic motion problem!
http://mathworld.wolfram.com/DampedSimpleHarmonicMotion.html

by the way this webpage kicks ass so write it down. i hope they get it in malaysia!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


(edit: deleted extra ! for readability)

[This message has been edited by Prometheus (edited 01-05-2003).]

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Originally posted by KING_GAMER:
This was discussed by in a book i read part of... Alice, in alice wonderland makes a joke about falling though the center of the earth..

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please dont base anything on alice in wonderland in reality.cause all that wuz written wuz from the mind of a hardcore acid head man.seiosuly fucked up dude wrote that.cant base shit all on t hat.

hahahah
if you can survive the molten heat in the center.
since the gravity is basically 0 in directly in the center of the earth.
what would basically happen is this provided you didn't have any fuckin air resistance either.
You would start flying down right through the center picking up speed.
and reach a point of terminal velocity then slingshot to the other side finally to be stopped exactly the same height that you dropped on the other side.
So if the altitude is higher on the other side. yer shet outta luck and will bounce back to the other side.
this is a really stupid question.
You do realize that all this question is based on that there is no air, no friction, and going STRAIGHT DOWN.
hahahahahahha.

Some scientist dude (i can't remember his name) has shown by experiments up here (on the surface) that if "average" air (ie average mix of O2, CO2 etc) were to surround our earths core the heat would make the molecules move so quickly that they would reach phenominal speeds and rush "upwards" (or where there is the bigest density of cooler air pushing downwards). Therefore he suggest that if an object were to be dropped "through" the earth then it would either be pulled down by gravity and be held in a posistion about a 2/3rds of the way (from the surface) down the hole or it will gather enough pace to pass the core and then end up being held on the other side of the earth about 2/3rd in from the surface.

-Chunk

Edit- Although digging a hole directly through the core and out the other side would be impossible, even if you could solve the problems of:
breathing in such an environment
standing the heat
being able to dig out the other side (ie upwards)
it would still be impossible because of all the gravity- the soil would tumble in above you to even the burden (thats why planets are spherical)


[This message has been edited by Chunkmiester (edited 01-05-2003).]

Ok, I'll buy the initial rush of superheated air. But wouldn't it reach equlibrium at some point, because the hot air at the bottom is not being replaced by cool air.

I can't remember whether its convulsion or convection where either a liquid or a gas is heated at only one point and that liquid or gas heats and rises at that point creating a void below it (therefore "sucking" in more gas/liquid to fill the void beneath it). Wouldn't that keep a constant supply of air?

-Chunk

Convection. However that doesn't apply to narrow vertical passages. Normaly in convection air travels a circular pattern, rising near the heat sourse, traveling away from it and cooling, dropping away from the heat sourse, then moving towards the heat sourse to complete the cycle.

This wouldn't apply in this sort of tunnel, mainly because the heat sourse is so powerful and because there is no return path for the cool air.

If you fell through a hole in the centre of the Earth, there is no way you will come out the other side, as your Gravitational Potential energy would be transferred into kinetic energy, but a significant amount will be lost as heat, light and sound. If you were to come out the other side then you would need to GAIN energy and not LOOSE it, and thus wihout an external/artificial means of propulsion (i.e. A rocket) helping you, you will simply go straight towards the other end, but stopping before you reached the end of it, and then bieng pulled down by gravity again to the other side, which is the side you originally jumped off from, and stopping even further off from the holes exit then you were at the other side (as you continue to loose energy as light, sound and heat), and so on (slingshot effect), until you have finaly run out of energy and come to rest at the centre of gravity in the centre of the earth.

However, if you did have a strong means of artificial propulsion, then you will be able to exceed escape velocity and come out the other side.

Just telling you what I know, and I am 15 BTW.

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Convection. However that doesn't apply to narrow vertical passages. Normaly in convection air travels a circular pattern, rising near the heat sourse, traveling away from it and cooling, dropping away from the heat sourse, then moving towards the heat sourse to complete the cycle.

This wouldn't apply in this sort of tunnel, mainly because the heat sourse is so powerful and because there is no return path for the cool air.

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You are much smarter than me when it comes to science so i know that i will end up as the loser of this "discussion" but bare with me for a minute:

When the hot air rises it would create (or eventually create) a void below it. This void, which i think is technically called negitive pressure, will be sucking things in towards it. As the easiest thing to suck in the vacinity would be the air i would have thought that either the cold air would be pulled down or possibly the hot air would stay in a near constant posistion (unable to move down because of the heat and unable to move upwards because of gravity and the negitive pressure below it).

-Chunk
*Waits for Prometheus to prove him wrong*

You would have a huge pendulum. Assuming no air resistance, the pebble would accelerate until it reached the center of the earth, at which point it would decelerate until it began to fall again, at which point the whole process would start all over.

Yes but it will loose energy as heat, light and sound while doing so, and eventually it will run out of energy and come to rest in the centre of the earth

The second half of what you said was correct, Chunk. After the air expands to as far as it can it will reach an equilibrium point. After that the air wouldn't move any more than it would in any closed environment.

Two things to keep in mind; it is several thousand miles to the center of the earth, and the air pressure would be extremly high (too busy right now to look up the formula for determining how high). Thus air resistence would have plenty of time to work on any object dropped, increasing gradualy to slow it to a major degree.