Wednesday, April 17, 2013

E=mc2


A splendid day of spring in the wake of yesterday's double bombing of the Boston Marathon (I'm writing on Tuesday). But the Earth doesn’t stop in its annual circuit of the Sun. And it would take a bigger bang than those on Boylston Street to tip the planet on its axis. So let's take what gifts nature gives us here in New England, and lean with the planet toward the Sun.

The trees are budding. The daffs and narcissi are in bloom. The frogs are singing in the water meadow. Fiddlehead ferns raise their crosiers by the brook. This afternoon I'll be sure to see the first snake come out to bask on the path. The newspapers are full of trauma, carnage, heartrending tragedy, and the globe sails on in its year-long lopsided circumnavigation of our steady star.

Every second, at its hot core, the Sun converts 657 million tons of hydrogen into 653 million tons of helium, by a process known as nuclear fusion. The missing 4 million tons of mass are converted into energy (how much? 4 million tons times the speed of light squared). The energy makes its way to the Sun's surface where it is hurled into space as heat and light. The Earth intercepts about one two-billionth of this energy, or about four pounds worth of the vanished matter. The Sun never misses so slight a fraction of its huge bulk, but for the Earth it is the difference between day and night. And winter and spring.

Now, in April, those of us in the northern hemisphere lean toward the Sun. Its rays hit the surface more directly. In summer, about a millionth of an ounce of the Sun's mass falls onto our college campus; in winter less than half as much. A fraction of a millionth of an ounce of the Sun's depleted mass is all it takes to tip the season toward spring. We grab it eagerly. It lifts our spirits. And, by a strange metaphorical magic, it reassures us that good will triumph over evil.


(I made the above calculations more than thirty years ago when I was writing 365 Starry Nights. No one's questioned them in the meantime, so I'll roll them out again.)