# Free energy from gravity and pressure?

1. Sep 5, 2006

### Jota

Forgive me if this sounds ignorant; I have no professional knowledge of physics. But I've wondered if it is possible to obtain free energy from gravity in this manner: I remember seeing a documentary on an attempt to build the world's tallest building. Apparently, it could only be built so tall (a couple of hundred miles at the most I believe) before the foundations collapsed. The foundation would collapse because it would melt, and it would melt because of the heat which came from the pressure of all that weight on top of it. If someone built a similar structure, larger than any modern day building but still vastly smaller than the theoretical, I suppose we could call it "melting height", to the point where the foundation's temperature was elevated even a few degrees, would that not constitute a constant, "free" flow of energy, derived solely from gravity?

2. Sep 5, 2006

### dmoravec

it takes energy to build the building. This energy is stored in the potential energy of each part of the building. This is where that heat and pressure energy comes from.

3. Sep 5, 2006

### Staff: Mentor

...meaning that the heat generated at the bottom is created and dissipated while the building is beng built. It isn't continuously generated, and it would never be enough to notice.

4. Sep 6, 2006

### Jota

More ideas

Sorry if these questions sound dumb, but as I said I'm an amateur.

Some layers of rock are folded, yet the folding happened after they solidified. Often, it not usually, the bending happened not due to direct transfer of heat from contact with other hot bodies, but because of the pressure of overlying rock bearing down on them, the mantle welling up beneath, and the movements of tectonic plates from their sides. Correct? does that not constitute energy from compression and pressure?

Thousands of miles into the gas planets, the high pressure apparently creates large, liquid oceans full of hydrogen. Isn't it the tremendous pressure from gravity, air etc. that keeps it liquid? And these oceans are hot as well. Isn't this from pressure? Isn't that energy?

Finally, the issue of superfluids. What if one build a gigantic ring around a massive body in space (moon, earth, even the sun), filled it with superfluid, and put an object into orbit inside it. Wouldn't even it pushing aside the fluid constitute a kind of energy? And, due to the lack of resistance, wouldn't it keep orbiting as long as if it were in free space?

5. Sep 6, 2006

### Aether

Energy can be stored within a compressible media and then released later, but this is only like storing energy in a battery. The amount of energy stored (W) is equal to force (F) times displacement (d): $$W=F \cdot d$$, and the force (F) is equal to pressure (p) times area (A): $$F=p \cdot A$$. These equations also work in reverse when you un-compress the media.

Last edited: Sep 6, 2006
6. Sep 6, 2006

Staff Emeritus
Water power (dams and water wheels) and in a sense wind power and tidal power are all "free and inexhausible" sources of energy drawing on the gravity of earth (and also its rotation, hydrological cycle, gravity of the Moon, and so on).

7. Sep 6, 2006

### Ivan Seeking

Staff Emeritus
Of course, wind and water wheels are ultimately [mostly] solar powered systems.

8. Sep 6, 2006

### Staff: Mentor

Sure, but these rocks actually move. Your building isn't going to move.
That's a much more complicated question. A lot of the energy was created when the gas giants collapsed, but a lot is being generated internally by other processes. Either way, pressure is a form of potential energy and works similar to a compressed spring-mass system (which is what your building would be). It is in static equilibrium.
Didn't you just contradict yourself? How can there be no resistance if it is inside a fluid? No, that wouldn't work.

9. Sep 7, 2006

### K.J.Healey

I think he's talking about "superfluids" like Helium-4 or 3, which are liquid at something like 2K and 0.02K. They have properties much like superconductors insomuch as they have zero resistance to motion, and will actually have a thin layer climb up any surface it touches. They can also have continuous flow around an object.
But once again, this is pointless because if you have an object moving through a fluid that is impossibly easy to move, then that fluid will by its own properties be unable to move anything else. Thus it could never turn a turbine or anything and you could just treat it as vaccum.