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10 months ago in History of Physics By Varun

What even is energy, and do physicists actually agree on it?

I keep reading that energy isn't a "thing" but a mathematical tool. Is that actually settled, or are physicists still arguing about what energy really is?

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By Akash Answered 8 months ago

It's settled for calculation, unsettled for philosophy. In physics, energy is a conserved quantity—a number that stays constant over time for an isolated system. Thanks to Noether's theorem, we know this conservation arises from a deep symmetry: the laws of physics don't change with time. So energy isn't a substance or a fluid. It's bookkeeping. That said, historical puzzles (like where energy lives in an electromagnetic field) still spark interpretive debates. We know how to use it. What it is remains a lovely, open question.

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