Why does the night sky look a bit different after 100 years?

Question

I am using Heavens Above interactive Skychart and noticed that if you move the year by 100 year increments, the night sky changes, but not so much. What causes this?

In: Planetary Science

Answer 1

Because that’s a few trillion stars / galaxies all moving at incredible speed through space.

The question should really be “why does it move so slowly” and the answer to that is that because space is absolutely huge so moving millions upon millions of miles is barely noticeable at the distances involved.

Some of those little dots are ENTIRE GALAXIES moving around, countless billions of stars swirling around each other at stupendous speeds, over stupendous distances, being born and dying, for billions of years, and all you see of it is a tiny dot.

There isn’t a single thing up there that isn’t moving relative to us, no matter how close or far away.