studying non visible waves (CMB, hydrogen 21)

thanks for clearing that up for me
I know my questions may seem a bit silly but i jst want a better understanding of whats going on , and these questions are the things that magazines take for granted that readers know

There's no such thing as a silly question! The whole point of these boards is to give people a place to share their experiences and broaden their understanding of astronomy. If there's something you're not sure if this is a great place to ask!

Bart.

The only silly questions are those that aren't asked. I'm certainly glad you asked it - I've learned a lot from Bart and Al!

Cheers

Dave