Losing gravitational potentional energy

AI Thread Summary
The discussion revolves around the concept of gravitational potential energy in a hypothetical scenario involving a shoe and a planet. It explores whether teleporting the shoe further from Earth would result in a loss of gravitational potential energy, with the argument that the shoe alone does not possess this energy—rather, it is the shoe-planet system that does. The conversation touches on different formulations of the Lagrangian, suggesting that any 'lost' potential energy could return to a global energy constant. Ultimately, it concludes that teleporting the shoe would actually result in a gain of potential energy, prompting further inquiry into the reasoning behind this assertion. The debate highlights the complexities of defining and locating potential energy in physics.
Tachyonie
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Ok, just a crazy idea of mine since I am bored, and arguing with itisali does not amuse me.

Imagine universe with nothing in it appart from a single planet, let's say something like earth. Now let's imagine that 100 km above the Earth you have a shoe. The shoe has some gravitational potential energy.
Now what would happen to that energy if I was to teleport that shoe another 1000 km further from the earth, without using any of the energy the shoe already has. Would it lose some of its gravitational potentional energy? And where would it go?

Tachyon.
 
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The "shoe" doesn't have gravitational PE, the "shoe + planet" does.
 
I've seen this suggested somewhere. In the Lagrangian for the shoe/planet system, the potential energy of the shoe is negative

L = KE - PE

and some people object to this and prefer to write

L = KE + K - PE

where K is a large valued constant, representing a 'global pool' of energy. Changing the Lagrangian like this does not alter the equations of motion.

In this scenario, you could say that the 'lost' potential energy has gone back to K.

But this means that dK/dr is not zero and the EOMs have changed. I think this illustrates the difficulty in locating potential energy.
 
If the shoe was suddenly teleported then it would gain potential energy, not lose it.
 
Why would you bother using a shoe? I mean, isn't it much more fun to propose teleporting a kitten?
 
Riogho said:
Why would you bother using a shoe? I mean, isn't it much more fun to propose teleporting a kitten?

I am not a sadist who tests equipment which doesn't even exist yet on poor kittens and risking that the head will be teleported inside out. Thats why... murderer!

ObsessiveMathsFreak said:
If the shoe was suddenly teleported then it would gain potential energy, not lose it.

Id love to know why!

Tachyon.
 
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