How sure can we be that electromagnetic waves do not require a medium?

Question

It seems to me that only the theory (Einstein Relativity) does not include or require such a medium to exist. But it must be possible none the less?

Sound waves
Water waves
etc...

They all require a medium.

Answer 1

"How sure can we be that electromagnetic waves do not require a medium?"



Really sure, actually. We know that "electromagnetic waves" are a description meaningful to only one classical model, Maxwell's equations. We know that "electromagnetic waves" are just photons, quantum objects. Bunches of them.



"It seems to me that only the theory (Einstein Relativity) does not include or require such a medium to exist. But it must be possible none the less?"



No, absolutely not. NOT present at the quantum level, and such a crutch fails in any scenario that includes gravitation. So Nature clearly has no aether, other than the Universe itself.



"Sound waves

Water waves

etc...



They all require a medium."



And they all transmit momentum differently than does light. It is a crutch. You can continue to lean on it, but it will prevent you from reaching further. Too many people wasted their lives trying to make an aether work. Please do not add to their number.

Answer 2

We can be certain because of two things:

1. They travel without a medium, as in an absolute vacuum.

2. The speed of light has been measured to be the same (within the accuracy of the measurements) for starlight reaching the earth six months apart. Because the speed of the earth in its orbit would be figured into any intervening medium, there is none.

Answer 3

Electromagnetic waves can travel in a vacuum. Take for instance sun ray. If you are standing on earth, sun ray gets scattered in the medium (air) and you see the colours of the sky. But if you are in the space where there is no medium, you won't see any colour in the sun ray. Real mediums exist and they introduce loss in energy propagation. Hypothetical lossless mediums will not make the sun ray look any different from how it looks like in the space.

Answer 4

In Kaluza-Klein theory a forerunner of modern string theory,electromagnetism is a distortion of space-time

Answer 5

electromagmetic waves, as far as I am aware, consist of photons, therefore they do not need a medium. We can still see EM light from stars in the sky, and it must have travelled through parts of space that do not provide a medium for travelling through.

Answer 6

nothing is certain, but certain theories test out better than others, these are essentially the best guess.