# What is the phemonemon behind electromagnetic waves being able to propagate in the vacuum?

I'm recently picking up interest about some aspects of physics, I never really studied physics apart from some basics and I'm having trouble finding a good course explaining the theorical approach without diving into maths (too much).

I'm interested in understanding how does electromagnetic waves work and was wondering what makes them propagate. I'm so used to mechanical waves needing a material to propagate that I'm having a hard time grasping that it's doable in a void.

From what I understood, for an electromagnetic wave to appear we need some energy exciting the electronic cloud of an atom to make its electric field "flickers" and thus creating a magnetic field, which will "disturb" the electric field, which will "disturb" the magnetic field and back and forth...

Do I have this right so far ? And if yes are those disturbances what we call electromagnetic waves and are traveling at speed of light ? I just can't grasp how a field can propagate so fast and so far

• Light and other electromagnetic waves do not require a medium. It carries the energy itself. Change in electric field, creates a magnetic field. Change in magnetic field, creates an electric field. It keeps rippling forward.
– Mast
May 21 at 19:15
• @JosB: the "amount of fields" is only as gigantic as it was in the first instant, because there is always energy conservation. So, when a spherical wave spreads from say an antenna about 0.1m wide (microwaves) to say 100m, its field amplitude will have shrunk to 0.1/100=0.001 to the power of two, i.e. 1/millionth. You can imagine how small the amplitudes get when the EM fields travel for one second (gigantic 2.99 x 10^9 m). May 21 at 19:28
• Here is a math-free classical explanation - In what medium are non-mechanical waves a disturbance? The aether?. And here is a more quantum mechanical one. How can a red light photon be different from a blue light photon? May 21 at 19:35
• The field doesn't shrink much since there is conservation of energy. Light travels nearly without losses throughout vacuum, 8 light minutes is a relatively short distance.
– Mast
May 22 at 6:36
• @JosB: no, the frequency does not change. If it's red it stays red, if it's blue it stays blue, and if it's infrared, it stays so. The intensity is what decreases. The fact that we can see light from the sun although the sun is 159 million kilometers away is because the sun at its surface shines so blindingly bright that after travelling 8 lightminutes there is still enough intensity so we can see it. If the sun was as bright as a candle, we wouldn't see it over that distance. The intensity fall-off is proportional to the inverse area of the sphere the light is currently at, i.e. prop to 1/r^2 May 22 at 8:47

• In equations what I mean is that in the wave equation obeyed by the vector potential, $\square A_\mu = 0$, it is not necessary that $A_\mu$ represents displacements of particles from equilibrium (unlike what you would expect based on an analysis of waves in an elastic medium). May 21 at 21:07