## Physical Forces That Make Life Possible

I have a bicycle wheel that I use to demonstrate circular motion and forces to my physics students. Some of the forces that we can demonstrate seem to contradict common sense, but they are physical forces that make life possible.

The wheel has a handle on both sides. If you spin it rapidly and put one handle in the crotch of your hand between your thumb and first finger, you can completely let go of the other handle, and the wheel will stay in place, seemingly defying gravity. As the wheel slows down, it begins to wobble, and the slower it goes, the more rapid its turning motion is. This is called precession, and it applies to all spinning objects.

Several years ago when I was teaching this unit in my physics class, I did this demonstration. My class skeptic, who tried to make sure I knew he wasn’t impressed with anything I did, said: “OK – big deal, how does that mean anything to me?” My reply was that he wouldn’t exist if the universe had not been designed with these laws in place creating the physical forces that make life possible.

We live on a globe spinning at roughly 1000 miles per hour. The globe itself is revolving around the Sun at 67,000 miles per hour in a solar system that is orbiting the core of our Milky Way galaxy at 515,000 miles per hour. Each of those motions involves forces that make life possible. We would not have weather moving heat and moisture around the globe without the rapid spinning. The Earth would collapse into the Sun if we weren’t traveling at such an enormous speed. The solar system would collapse into the core of the galaxy and be absorbed by the black hole that holds our system together if we weren’t moving fast enough to avoid such a thing happening.

We understand these fundamental laws of physics, but our observations tell us that the picture we have painted here is oversimplified. Stars on the outer edges of the galaxy are circling at roughly the same speed as stars near the core, and that should not be happening. We know that there must be dark matter filling in for the lapses in speed that we measure. Either that or the darkness is simply in our understanding.

The reality of the motions and physical forces that make life possible on Earth are there for us to examine. However, the implications of what we see defy our imagination and speak of the reality of the God who designed and created it all.

— John N. Clayton © 2019

Data from Notre Dame Magazine, Spring 2019, page 47-49.