Living away from New England for so long, I had forgotten how stifling, hot, and humid Boston summer weather can be. I'm remembering it now, here among the hum of air conditioners and fans and the whining buzz of mosquitoes. The TV flickers ceaselessly in the dim den, and a moist vegetable darkness surrounds the house. After the Red Sox game is over and won, it's time for physics.

I couldn't resist the title. Newton is a large suburb of Boston, and some of my relatives live there. These suburbs of Boston were settled by Europeans during the time of Isaac Newton, and even though I'm plugged into twentieth-century technology, I'm still in the seventeenth century when it comes to physics. Or even the sixteenth. I've been introduced, in my book, to Kepler's laws of planetary orbits, and those heretical ellipses. And his third law: "For every planet, the cube of its distance from the sun is proportional to the square of its period of revolution." There's the Harmony of the World, the first maps of the clockwork universe of the coming Enlightenment.

How did Kepler find out about those squares and cubes? According to my book, he used "data acquired through years of accurate observation by the Danish astronomer Tycho Brahe." And yet the formula seems so simple, expressed by ordinary algebra. These are the "giants" whose shoulders Newton stood on. My book, the tireless and un-botherable instructor, shows me how Newton derived his formula for universal gravitation from Kepler's laws of planetary motion. Though the book doesn't show all the algebraic steps, I try to derive them anyway, according to what I've learned. I cross-multiply proportions, and substitute one entity for another, attempting to move from one stage to the next. I scribble math graffiti all over the margins and between the paragraphs. It seems to make sense, but why? Why should a simple algebraic substitution or proportional statement or even solving for one variable, say something so important about the universe? Perhaps I am misunderstanding how theory is derived. But I continue to be in awe of Kepler time and space, and Newton mass.

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