Thanks for all of the replies....this gives me the explanation I need to
understand background radiation.
To answer some of John's commentary...... really the purpose of my
question is so that I can understand background radiation. I know how
science works in that the best possible explanation is what we go with
at the time. However, background radiation is purported by texts and
videos to be "supporting evidence" for the Big Bang. I wanted to
understand that claim a bit more.
As far as the red shift activity, I do something from Project Astro that
shows why we can observe the expansion from any point in the universe
(like earth), which isn't necessarily the "center" per se. It has
students calculate the age for the universe based on how much galaxies
appear to have moved in a certain amount of time (the materials are two
copies of many dots, the top one a transparency with the dots expanded
on a copier). Students can easily see the expansion with these
materials, and see that the expansion is greater/faster the farther away
you get from a reference point.
I do the red shift activity when I do the electromagnetic spectrum, and
then come back to touch on it again when I do a unit on sound. So they
get a few perspectives on what it means for wave/light/sound to be red
shifted.
This is for most students the first exposure to this concept at all, so
it is a superficial introduction, certainly.