Gravity

If it was possible to construct a tunnel straight through your planet called Earth,from one side to the other,land mass to land mass obviously and you were able to travel through this unharmed,regardless of the heat from the core,where would you stop in relation to gravity ??

I'm not sure about this but it would seem logical that you would stop as close to Earth's central mass point as possible. This would be about half way through I guess.

Actually, it would depend on whether there was any air in the tunnel: If so, the air resistance would slow you down, and you would continue past the centre of the earth, rising to a point lower (on the other side), then fall back down to the centre. Effectively, you would bob up and down to the other side and back again, each journey not quite as high as the one before, until, just like a pendulum, you would come to rest at the centre. If, however there was no air resistance, you would continue to bob up and down more or less forever. All this of course assumes that your tunnel is from pole to pole, because if not, the effect of the spinning earth would be that you hit the side of the tunnel, and (depending on friction), you would probably slide down to the centre. Probably.

to that of a perpetual trampoline effect ?.

No... You would be completely ripped apart at the center... You would never stand a chance, the force of gravity would increase as you approached the center.

Not really, WellRounded.  Assuming the centre of your body was exactly at the centre of the earth, then "above" you would be half the mass of the earth, pulling you "upwards" with a force of half your weight. And "below" you would be the same. So effectively you would feel the weight of half your body pulling up and the same pulling down. Now, if you can hang by your hands, say from a tree or something, without being ripped apart, then you should survive the force at the centre without a problem. Because in fact, you could consider 6 directions (relative to your body), up/down, right/left, forward/back and you would feel an equal pull in each of those directions, of 1/6 of your weight. The more opposing directions you consider, then the less weight or pull you will feel in each of those directions. However, as humans are usually longer  than they are thin, taking into account just "up" and "down" is probably a good enough approximation. Unless you were curled up into a ball. I think I would curl up into a ball, if it happened to me. And of course you'd be moving so fast, that the full effect of the opposing forces would be barely noticeable.

So yes, bayview, a perpeptual trampoline effect.

So we have to learn either how to control,manipulate or develop this to a potential form of transport even to the extent of channelling the unlimited power source ie gravity across land as opposed to through it.

Now to make gravity act differently,(up-down) what entity controls,(left-right) something must ? otherwise we would be living very close to each other :-)

Seriously in bending or persuading gravity to run parallel would be possible ?

replies interestingly awaited.

Lets say that you actually construct such a tunnel, where would the magma that you pulled out go? When you get there you would be vaporized from the heat, and crushed.  What would the tunnel actually be constructed out of through, if it's hot enough to melt and rock, as well as turn it into a superfluid, maybe I'm out on a limb for that part, nothing on this Earth that has been found that could withstand that.

You also forgetting that when you go in the Earth that your weight would be in equal sides, and there would be nothing, save your flesh, that would protect you from it. You can't stop the gravitons, they are always there; even in space it's not called zero-gravity, it's called microgravity.

The wight of gravity won't stop because there is another force pushing you from the other side, it would simply crush you.

@shadowslayer,

I think that as you dug the magma out (leaving aside the construction of the tunnel, for the moment), you could bring it to the surface and use it to vaporize the ice at the poles, creating steam which could power massive electrical generators, and store the energy in massive batteries (or fly-wheels, or some other kind of energy storage device). This would solve the energy crisis, we wouldn't need fossil fuels anymore. Pity about the polar bears, though. And the people living on islands or near the coast.

Constructing the tunnel may not be such a big problem, either. When you started digging, the waste would of course be quite cool, it only gets hotter as you go deeper. Say you dug deep enough, so the temperature was about 200 or 300 degrees C, that would be enough to vaporize ice into steam, and is easily contained - current technology is quite able to contain higher temperatures than that. As you dig deeper, the top-most layer would start to cool down, causing hot air to rise up through the tunnel, this also could be used for power generation. As the top layer of magma cools down to a managable temperature, you just dig it up and haul it up to the surface. Of course you might need side-tunnels also, because there would also be magma surrounding the tunnel. But this would help with the primary objective of the exercise, which I presume is transportation?

I envisage starting with maybe 3 tunnels, one pole to pole, and two equatorial ventilation tunnels, one from 0 degrees to 180 degrees longtitude, the other from 90 to 270 degrees. Because of the earth's spin, the equatorial tunnels might not be so useful for transportation, but they would surely help with the disposal of hot magma - the entrance/exit holes would in effect become giant volcanoes, spewing out hot magma, which can also be used to generate electricity.

I'm not sure about all this talk of gravity crushing people - every day you walk around subject to the full might of the earth's gravity pulling you to its center, and I don't hear many people complaining about it. Except for people falling off skyscrapers, cliffs and the like, but if they are complaining, well they shut up soon enough... Out of the four main forces which (according to physicists) hold this universe together, gravity is by far the weakest.

@bayview,

 <quote>Now to make gravity act differently,(up-down) what entity controls,(left-right) something must ? otherwise we would be living very close to each other :-)</quote>

The thing about gravity is, it acts equally in all directions at once, just a tiny, tiny amount from each elementary particle. However, there's an awful lot of particles in the earth (and in you, and in me) - but it takes the enormous number of particles in the earth to make things stick to the ground. And it is this direction, the line joining the center of your body to the center of the earth, which defines (for you) "up" and "down', so to talk of gravity acting in a left/right direction is somewhat meaningless, as it is gravity itself which defines the direction of up and down.

However, when you talk of gravity acting in parallel, or of bending gravity, that is indeed practically impossible according to modern day physics. The person who discovers a practical way of bending gravity will probably have discovered the deepest secrets of the universe itself, the speed of light, time travel, etc.

The thing is, it is certainly possible to bore a tunnel right through the center of the earth and out the other side, it's simply an engineering problem. Whether it is worth the enormous cost and time investment is a different question. However, bending gravity? Just not possible yet, and although such things may happen in or around black holes, science doesn't yet know how to do it.

I very much doubt that they would dump magma on the ice cap; water is actually one of the so called "greenhouse gasses" so dumping a few hundred thousand tons of it in the atmosphere would not sit well for the environmentalists.

Lets just say that we do manage to find a material that would withstand the intense heat. Where would we get it, and how would we get enough? Remember the analogy that the Earth is like an apple, and how the crust on the Earth is like the skin on an apple? The reason why they said that is because the crust is actually really small compared to the rest of the Earth.
We wouldn't collect metal from the asteroid belt because if we have advanced that much, we would have be getting our energy from Sol (the sun).

Do you wonder why when we leave the Earth, we don't get puled back in? It's because as we get further away, the gravity dissipates. So using that logic, gravity would get stronger as we get pulled into the Earth; much stronger, much much stronger.

If there was air in the tunnel the pressure of the air would crush you as you approached the center of the earth much the same way the pressures at the ocean bottom would crush you 

Hmmm ! with respect that sounds a bit like sailing of the edge of the world.

You'll have to explain that last comment.  Do you doubt my assertion?  If so why?

Quote: I very much doubt that they would dump magma on the ice cap; water is actually one of the so called "greenhouse gasses" so dumping a few hundred thousand tons of it in the atmosphere would not sit well for the environmentalists.

Damn troublemaking treehuggers! Round 'em all up and ship them out to the Amazon rain-forest (or whatever's left of it), and we'll hear no more from their kind! 

Qoute: If there was air in the tunnel the pressure of the air would crush you as you approached the center of the earth much the same way the pressures at the ocean bottom would crush you

Well, there might be some truth in this - the air pressure at the centre would be equivalent perhaps to several times normal atmospheric pressure, but don't forget that air is so much lighter than water, so travellers could probably be protected by a standard pressure suit. I don't think this would be a major problem, but maybe it would be better anyway to pump the air out of the tunnel, thus increasing the maximum speed of the traveller: this might not be such a bad idea if the heat problem is not solved, you'd want to pass through the center pretty quickly, I should think.

Quote: Do you wonder why when we leave the Earth, we don't get puled back in? It's because as we get further away, the gravity dissipates. So using that logic, gravity would get stronger as we get pulled into the Earth; much stronger, much much stronger

But you are forgetting that the gravity you feel at the surface of the Earth is due to the combined pull of every single particle in the Earth. When you are at the center of the Earth, every particle is pulling at you, outwards, so you feel this combined pull from all directions - you might think it would pull you apart, but it can't, because the combined pull of every single particle in the same direction would be no more than the pull you feel downward at the surface, but now the particles are all pulling in an outward direction.

Quote:Lets just say that we do manage to find a material that would withstand the intense heat. Where would we get it, and how would we get enough? Remember the analogy that the Earth is like an apple, and how the crust on the Earth is like the skin on an apple? The reason why they said that is because the crust is actually really small compared to the rest of the Earth.

But the magma and the crust is more or less the same stuff, i.e. magma is simply melted crust, or crust is just solidified magma, whichever  you prefer. Just as we now mine minerals from the crust, surely we would also find metals in the magma? In fact, to please the treehuggers, we can recycle some of the waste magma by using it to build heat-shields around the tunnel. (Treehuggers think anything is ok if it has the words "recycle" and "waste" in the same sentence!) We could call it something like, errm, Tunnel Waste Energy Recycling Project. 

Do Not under estimate a column of air 4,000 mile high  

I think you'd bounce between the two sides, slowing down with each go (due to air resistance and friction or somethn) and eventually stop at the core.