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Let us consider a closed waveguide, or a closed fiberoptic or more simply a perfectly conducting box.

Assume there are no wall losses or dissipation in this system.

Let us consider 2 versions of this system:

System 1) the box is empty

System 2) the box contains a huge amount of electromagnetic energy (resonant modes)

Can we say that the mass of these two systems are the same, since photons have no mass?

Can we say that the gravity produced by these two systems is the same?

Back to the basics !

Michel

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# Quiz: mass of photons, E=mc²

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