Does it though? At what frequency? In the limit of f=DC this is trivially not true.
Also, if that were the case, an airplane couldn't be made into a Faraday cage.
Also, the cage+Earth system would itself be an antenna.
If you need ground for a topologically imperfect cage, maybe… but I doubt it.
I think (but I don't know!) this is like the legends surrounding engine torque car guys believe. Electrical engineers putting everything to ground because they got burned
Also, if that were the case, an airplane couldn't be made into a Faraday cage.
Also, the cage+Earth system would itself be an antenna.
If you need ground for a topologically imperfect cage, maybe… but I doubt it.
I think (but I don't know!) this is like the legends surrounding engine torque car guys believe. Electrical engineers putting everything to ground because they got burned