# Electromagnetic waves in vacuum

If there is no source then also there is electromagnetic waves described by Maxwell equation. how if there is no source then existence of EM waves. What gives energy to this EM waves. Is it vacuum fluctuation or something else?

• In classical electromagnetism waves always have a source, it's just not always necessary to describe the source as part of the problem we are interested in. In that case we just write down the idealized free wave and the wave equations guarantee that it will propagate even in absence of a source. – CuriousOne Jan 5 '15 at 11:19
• my question is if there is only vacuum in the universe then whether there is generation of electromagnetic waves or not – Hare Krishna Jan 5 '15 at 17:26
• @HareKrishna, there isn't only vacuum in the universe, so you're starting off on the wrong foot. And if there was only vacuum (i.e. total quality-less void), then there would be no electromagnetic interaction as we know it, because there would be nothing it could possibly bear on, nothing it could be conceived in relation to, no place (in space or across all time) which it could come from or go to. – Steve Feb 3 '18 at 9:51

Remember that the Maxwell's equations are differential equations, i.e. they require boundary conditions. One of the things to have to fix is the amplitude of a wave $E_0$. You can set it to $0$ and have no electromagnetic waves whatsoever. But if you indeed have a wave propagating, then it means that $E_0 \neq 0$ and its value must be computed with information about how this wave was generated. For example, in the case of dipole radiation, you can compute the pre-factor.