I don’t mean wind energy, electricity, power but energy at a basic level (physics).
For example: is all there ultimately energy? Is energy (only) a synonym of mass? can there be eg theoretically a universe with energy, without mass ?
I read somewhere “the ability to do work”. Then I wonder: the ability of who-what? So is energy a kind of potential state? Which can also “be” in complete vacuum, without mass?
Answer
This is a very difficult question. Energy is one of the most important concepts in Physics. Yet we cannot give a simple general definition in a few sentences. Each type of energy can be clearly defined.
‘The ability to do work’ is a definition that is fairly general. For example, a moving mass can exert a force on a second mass through a collision and give it a speed. This mechanical kinetic energy can therefore clearly provide work. But heat (= the chaotic kinetic energy of the molecules of a substance) is also a form of energy and it is impossible to use all the heat of a substance to do work. So the definition isn’t quite perfect.
Essential to energy is that one form can be converted into another, but that the total amount of energy is preserved. In the course of history, for example, the concept of energy has expanded. Heat used to not be considered energy, now we do know that heat is a form of energy. Since the theory of relativity we also have to accept that mass is a form of energy. Ultimately, it is this energy that powers our nuclear power plants.
Answered by
Prof Walter Lauriks
Physics Acoustics
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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