# If sound waves travel by pushing particles back and forth, then how exactly do electromagnetic/radio waves travel through the vacuum of space and dense matter? Are they emitting… stuff? Or is there some… stuff even in the empty space that they push?

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If sound waves travel by pushing particles back and forth, then how exactly do electromagnetic/radio waves travel through the vacuum of space and dense matter? Are they emitting… stuff? Or is there some… stuff even in the empty space that they push?

In: Physics

Sound is nothing more than the vibration of those particles being pushed around. Electromagnetic/radio waves are actually energy itself, which doesn’t require a medium in order to move.

Radio waves and EM waves are forms of light. Part of the EM spectrum. The travel at the speed of light. They have no mass and don’t travel in a medium like sound waves.

150 year ago, people had the exact same assumption you did. If sound is a vibration/wave in matter, surely light must travel in something. Space appears to be a vacuum, so there must be something, even in a vacuum, that light/electromagnetic radiation vibrates in. This was called the aether. Some sort of fluid or such that exists in the vacuum.

Turns out the answer was no, light isn’t a vibration in anything. The aether does not exist. First Maxwell came along and showed that electricity, magnetism, and light were all the same thing. If you took the equations for electricity and magnetism and threw them together, you could solve the wave equation. Out popped a wave, traveling at the speed that light had been measured at. Light is an electromagnetic wave.

But an issue arose. The answer for the speed of light was always the same value. Doesn’t matter what reference frame you took, if you’re on a car traveling half the speed of light, the highbeams still travel at the speed of light This aether can’t exist, the light isn’t traveling at the speed of light relative to any fixed medium. Sound for example travels with the air. If the air moves (wind), the sound moves with it. If the entire atmosphere moves (the earth’s orbit), the sound moves with it. Like that is not like this, it doesn’t care what reference frame you use, always the same speed. As such, there can’t possibly be this aether that light is moving in, there no fixed medium for the speed of light. Surely something is wrong with our understanding of electromagnetics and Maxwell’s equations though. There’s no way the speed of light can always be the same, that just doesn’t work, it’s got to be based on how fast other things are moving, right?

Then alonge comes Einstein, and his theory of special relativity. Turns out the answer is that Maxwell’s equations are absolutely right, light always travels the same speed, full stop. Doesn’t matter the reference. Turns out space and time actually change to ensure light (or other massless things) always travel the same speed.

So there is no stuff, or as it has been historically called aether. Light, or electromagnetic waves, just are. The electromagnetic field is everywhere, and ripples in it are light. Turns out the rest of existence is like this too. Electrons, protons, neutrons, what makes of matter. Turns out these are also just ripples is a field that is everywhere, except they couple (stick) to another field that is everywhere, the higgs field, and this appears to give them mass.

So in space, light just is. In matter, light is slightly modified. Electrons and protons have electric charge, so they alter the electromagnetic field. This leads to light being slower in matter, and sometimes absorbed or reflected.