Milky Way From Earth

I did not have trouble imagining the Sun. It shows up in the morning and is gone at night. It is little and we can see it in a small patch in the sky. We move around it.

Only now I have to talk about galaxies. I was mystified some times when I pondered: Why do we see it if we are inside? I have my answer.

I saw a nice picture online of the Milky Way actually going up in the sky and coming down. The idea finally popped-out in my head.

There is one side, away from the center where we can actually see outside of our Galaxy, and one where we stare at the big black hole in the center.

Thus, sometimes we must see a patch of light coming out, and going down. Measuring the angular extent of this light we can estimate the size of the Milky Way.

Now I get it.