Slide 6 of 25

Notes:

Stars revolve around the center of each galaxy. In accordance with Newton's laws, the inner stars go around faster than the outer stars. So the spiral tends to wrap itself up, like winding up a clockspring. In our own galaxy, the observed speeds are so fast that the spiral would become a featureless disc in only 200 million years. The same dilemma applies to other galaxies, too.

Let's take a look at some spiral galaxies ...

Evidence for a Young World
D. Russell Humphreys, Ph.D.