I am a principle that is of interest to both physicists and chemists.

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You're wrong ❌

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Or????

I am a principle that is of interest to both physicists and chemists.
I am encountered in statistical theories of matter.
I am derived in kinetic theory.
My currency is half the Boltzmann constant times absolute temperature.
For a given temperature, I assign equal energy to each degree of freedom.
Answer: Equipartition principle (or Principle of equipartition of energy)

the Equipartition theorem

Next one

I am an experiment that was performed towards the end of the nineteenth century.

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This one is correct 😂😂😂

I am an experiment that was performed towards the end of the nineteenth century.
I was billed to prove the existence of something that is now known not to exist.
Such was my success that a new approach to physics emerged from my results.
I am named for the two scientists who first performed me.
I am just an experiment that saw the end of the luminiferous ether and provided a nail for its coffin.
Answer: Michelson-Morley experiment

That's crazy 😂😂😂

Next one😊

Should it be our last riddle ??😔😔😔

I am a law in physics.

Yesss😂😂😂😂