If you think that anyone whose profession is anything actually to do with astrophysics is eye-balling “not-space” out there in outer space, you’re foolish and not to be trusted.

I haven’t kept up with the the improvements in monitoring “not-space” (by which I mean to capture everything that is literally not empty space, like rocks and “processes” such as stars), but here is a short history, followed by a picture from a popular science book from the early 1900s on the topic.

Can you picture holding a small prism in such a way to cast a rainbow on the wall or floor? Good. Now please do the same with a second prism. Thank you. Now measure the difference between the two rainbows, as intricately and completely as possible. That is how “scientists” actually determine what the “not-space” is, how fast it is moving, and how far it is from us etc.

Here’s the example from a real astrophysicist.

This is from Sir James Jeans’ The Universe Around Us.

To be sure, no one is watching bright spots with their naked eye, videos of bright spots with their naked eye, looking through telescopes for a long time, or anything like that when determining anything about “not-space” in outer space.