But waves do travel at different speeds. In fact, different frequencies travel at different rates in different media. Only the speed of light __in a vacuum__ is constant. Which is pretty rare. So rare that even space doesn't have a pure vacuum, though 1 hydrogen atom per meter is pretty close if you ask me.

But I did notice the pun.

> someone is going to think waves travel at different speeds

That's a good thing, right[1]?

Something about "the one thing all models have in common..." comes to mind.

[1] https://en.wikipedia.org/wiki/Velocity_factor