Dear The law of conservation of energy implies an isolated space, such as eg the earth incl. atmosphere.
Since the beginning of space travel, we have been exporting energy and mass without returning it in its entirety. Compared to the mass of the earth it may be almost negligible, but somewhere the law is no longer correct.
Suppose we hypothetically fill the moon with terrestrial material, both the energy and the mass come from the earth as the mass of the moon increases. What would happen hypothetically if we did this to an extreme degree E.g. increase the lunar mass by 1% ?
… or is all that belongs to the gravitational pull of the earth part of that isolated space? But you can go on like this to our solar system and eventually to the universe with the great mystery: ‘infinite’.
Answer
Yes, the law of conservation of energy remains a solid principle that we should stick to. On the one hand it follows mathematically from the basic laws of physics, the definition of energy as a conserved quantity is a way of formulating those laws. On the other hand, whenever an apparent contradiction has occurred, the conservation law has also stood up experimentally.
In the example you provide in the context, you talk about an ‘isolated space’, and then you continue to reason about the masses that have left the Earth without returning. Surely that means that the Earth is not isolated space? If something departs from here, it takes energy elsewhere. But the total energy of the larger system remains the same.
Answered by
Prof. dr. Christopher Waelkens
Astronomy
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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