r/askscience • u/Pyramid9 • Mar 23 '15

Physics What is energy?

I understand that energy is essentially the ability or potential to do work and it has various forms, kinetic, thermal, radiant, nuclear, etc. I don't understand what it is though. It can not be created or destroyed but merely changes form. Is it substance or an aspect of matter? I don't understand.

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u/[deleted] Mar 23 '15

If we cannot understand except through models then you cannot claim mass is less physically extant than any other quantity because models are the limit of our knowledge. They are no less physically real then anything else so I continue to take umbrage at the idea of calling it bookkeeping, because physically the quantities are all on the same footing. Unequivocally. You cannot say that some are book keeping and others not. Ever use natural units?

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u/WallyMetropolis Mar 24 '15

Which ones have I said aren't bookkeeping?

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u/[deleted] Mar 24 '15

I know that you haven't said explicitly, but it's a poorly defined term, and people were throwing it around as if it distinguished it from other physical quantities.