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Q & A: gravitational energy

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Most recent answer: 10/22/2007
Q:
If the law of conservation of energy is true, how does it explain work produced directly from gravity. Using hydro-electricity as an example, I understand that falling water looses potential and that this loss of potential mathematically accounts for a fuel being consumed to produce energy. However without gravity the water wouldn’t have the ability to gain a potential and thus gravity is really the driving force and the creator of the work. However science has not found any arena where gravity is actually diminishing a fuel and thus the “fuel” source would be unlimited. This would clearly contradict the both the laws of conservation of energy and mass (can’t be an infinite supply of either b/c then neither is finite and the system of keeping track of units breaks down). Can you shed new insight on this topic for me?
- Pat (age 25)
Chemical Industry, USA
A:
When the water falls to the state of lower gravitational energy, it's not available any more to drive an engine. So the 'fuel' is indeed diminished. It's true that more replaces it, because water evaporates and returns to high altitudes. That process is driven by solar energy. The solar energy comes from a type of nuclear fuel, which is also being used up.

Mike W.

(published on 10/22/2007)

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