(January 9, 2020)
let us trek sublime
to simple – it’s a fun route
no pulls but all push
that’s physics – nutmeats all shelled
center-of-gravity is the point!
*(B. J. Crain prefaced one of his few off-the -cuff mathematics lectures in what then passed for Sanford (Florida) Junior High in a building which began life as a high school and now serves as a middle school. B.J. told those few of us who listened that there was no such thing as a pull. WHAT!? HOWZAT? He had captured the class. Take a wagon handle – you know, the little red Radio Flyer? – the force you expend on “pulling” it down the sidewalk as a tyke? Where was your hand? On the handle’s little loop for a grip? Your hand was pushing against the back of that hand-hold as you “pulled” the wagon. Take a rope – any kind will do: when you “pull” on the rope does your hand (or both hands) bend the rope to get the proper angle to apply force? Did you notice you were bending the line at right angles to the length of rope in order to exert your “pull?” In fact, you were pushing against the bent rope at right angles to the line. Now, take gravity. Please. (Pardon the joke: couldn’t resist – I was pulled into it by a synapse firing!) The attractive force which impels (or compels if you like) the smaller object toward the larger object (you know, greater mass attracts the smaller mass, right?) is through the center of gravity of each body: the center of mass of the smaller object is “attracted” toward the larger by means of a push, not a pull at all. Go, ask your math – or astrophysics – teacher. Just don’t try winning a bar bet: B. J. might already have beaten you to that particular mark.)