## energy, $$E$$

https://doi.org/10.1351/goldbook.E02101
In mechanics the sum of @P04778@ and @K03402@. In thermodynamics the @I03103@ or @I03103@ increase, $$\Delta U$$, is the sum of @H02752@ and @W06684@ brought to the system. Only changes in energy are measurable. For photons $E=h\ \nu$ where $$h$$ is the @P04685@ and $$\nu$$ the frequency of radiation. In relativistic physics $E=m\ c^{2}$ where $$c$$ is the speed of light and $$m$$ the mass.
Source:
Green Book, 2nd ed., p. 12 [Terms] [Book]