OT: The 10th Demention

[Raapys]

Hmm, I definitely see your point in the spring and bullet scenarios, where it's obvious that there is energy waiting to be released, but with gravity too?

To clarify my question: If we had a device that could read the potential energy we're talking about, then that device would generally, in the case of a compressed spring, come up with the amount of energy used to compress it, right?
But would you also be able to "find" the ( potential ) gravity energy?

I guess my point is, isn't the potential energy of the spring real, i.e. it's actually in the atoms and can be measured, while the potential gravity energy isn't ?

[Suicide Junkie]

Why would you think gravitational potential energy is not real?
You drop a bowling ball, and it crushes your toe. That's definitely real energy.

On the small scale, it simplifies to mgh. For larger scales you need integrals. But it is all very straightforward.

The only difference is scale. In the spring, you have electric forces pushing or pulling (but you have to look on the molecular scale). Gravity works on scales big enough to see and just pulls.

BTW, since gravity is always attractive, the arbitrary zero point is generally placed at infinity. So if you fall inwards, your gravitational potential becomes negative.
Conveniently, setting the point there means that if your total energy is positive, you can escape. If the total is negative, you're stuck in the gravity well unless you steal some energy from something else.

[GuyOfDoom]

I think what is trying to be said is that if we understood enough about gravity we could potential control it and generate a "limitless" supply of PE since gravity only weakens over distance and not time.

[Suicide Junkie]

*Sigh*

[GuyOfDoom]

I realize the point you're trying to get across, but the end all be all is the fact that the mechanism behind gravity is still a mystery. The definitions of energy are left intentionally vague because we don't understand them completely.

Gravity is a property of matter, but how is it "enforced." That's where gravitons come in.

[Suicide Junkie]

ALL the fundamental forces do not fade with time. Gravity is nothing special.

The only reason why everyday forces fade is because they do work on stuff and thus dissipate the energy into the environment.
If you don't let your Bowling ball fall, it dosen't lose any potential energy. If you don't let your spring expand (or rust out!) then it dosen't lose any energy. If you don't let your flywheel interact with the environment, it won't slow down, but it will still be exerting a lot of force to keep the outer edge of it moving in a circle.

Conversely, if you use a realistic flywheel, the bearings will introduce friction and sap your kinetic energy into heat and noise.
If you use a realistic spring, it suffers chemical reactions, and metal fatigue.
If you have your bowling ball sitting outside, it will sink into the mud.

[Raapys]

I'm just not sure what the difference would be between saying that "This object has potential gravitational energy that is being transformed to kinetic energy as it approaches another mass" and saying that "Gravity creates kinetic energy in this object as it approaches a mass, or destroys it as it moves away from a mass".

The first one corresponds with the energy conservation law, the second one does not. Can it actually be proven that the first one is more true than the second?

The reason I mentioned potential gravitational energy not being real is because it can't be put on a weight. I mean, you can weigh 'normal' energy, since it actually has mass, but gravitational potential energy doesn't, to my knowledge.

[Fyron]

There is a huge body of empirical evidence supporting the veracity of the conservation of energy law.

[AgentZero]

Veracity is one of my favourite words.

[capnq]

Suicide Junkie said: ALL the fundamental forces do not fade with time. Gravity is nothing special.

"Constants aren't. Variables don't."

Paul Dirac speculated about the gravitational "constant" varying over time all the way back in 1938. This article lists the current upper bound for how fast it could be changing. Some versions of string theory allow for the possibility that other "constants" also change over time.