[Geminidog]

It's also clear meaning light passes through this baryonic matter.

My question is, how do we know that the "dark matter" we assume to be littered all over the universe isn't just clear baryonic matter?

I know that we infer the existence of dark matter through gravity so how do we know that this dark matter isn't just "clear" baryonic matter?

Any astronomers care to share their expertise?