That's what they tell us. Light can travel through a vacuum with nothing in it. And maybe so but what is the evidence?

So I looked up the best vacuum on planet Earth. It contains 2.5 million molecules of air per cubic cm. This is said to replicate conditions between stars. So how then can we say we've ever tested light waves going through "nothing". We haven't.

To test the validity of my suspicions I've asked the science guys on reddit if they have an answer for this. The first few responses have already been hostile and that usually indicates this is one of those issues they simply don't have a good answer for. I was very polite in my question btw, so no I didn't provoke anybody, this is all on them.

We'll see how it goes. I'm open to a good explanation of why this is a valid test, but this light has 2 million molecules to interact with ever cubic cm it propagates, so you didn't rule out matter.