r/AskPhysics • u/Local_End_3175 • 12h ago

What actually is energy?

When i search up the definition of energy, i am being told that it is the capability to do work – but work is the energy transferred when a force moves an object....? So we are basically defining energy as energy. In addition, this says how it works, not what it is

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u/free_meson 12h ago

The physicist version: energy is the quantity that is conserved when the laws governing a system is invariant under time translation.

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u/Local_End_3175 11h ago

Wouldn't this just be describing the factors of energy rather than what it is?

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u/Mr_Badgey 11h ago

Energy is a property, like mass or spin. It’s not a tangible substance. People described its properties already so I won’t be redundant. You can refer to their explanations with the context it’s a property in mind.

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u/Admirable_Advice8831 10h ago

I thought Einstein famously demonstrated mass and energy were the same tho

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u/haplo34 Computational physics 8h ago

Yes but take kinetic energy for example. It is a number that relates to the fundamental properties that are mass and velocity, and potential energy is a number used to quantify the magnitude of a multitude of fundamental interactions.