For electromagnetic waves, as i understand it, there isn't actually movement up and down in space; there are oscillations in the electric and magnetic fields. Which do somehow have a spatial direction, which is why light can be polarised. I don't have an intuition for it at all!
The challenge with the longitudinal example, which is of course technically correct, is that it’s hard to map it to the spherical shells that most of these phenomena radiate into.
https://www.youtube.com/watch?v=GIkeGBXqWW0
https://www.youtube.com/watch?v=kxQj-wPePBU
For electromagnetic waves, as i understand it, there isn't actually movement up and down in space; there are oscillations in the electric and magnetic fields. Which do somehow have a spatial direction, which is why light can be polarised. I don't have an intuition for it at all!