Goodbye to the longest day of the year

It's the summer solstice, the longest day of the year. At quarter to nine, there was enough light to see clearly and walk outside. A quarter moon was high in the clear sky, still blue from the hot midday, not yet given up color for blackness. I thought of the telescope I got for Christmas nearly 50 years ago, packed in its box in a closet. I should get it out and look at the long shadows cast by the sunlight on the hills and craters of the moon, but unpacking the scope, setting it up, then taking it down, would take too long. I settled for a long, bare-eyed look at the moon floating high in the sky.

Today's heat was a reminder of solar power. The aluminum knob atop my car's shift lever was blistering hot when I left the office. Stepping from the cool office to the late afternoon heat made me gasp, and the enclosed car sitting in the sun was hotter yet. Temperatures in the 90s are predicted all week. Although on this day the sun takes its most direct aim at this place, late June is usually not the hottest time of year. Usually that comes in July or August after the Earth's surface and atmosphere and cloak of seawater have had a few months to absorb and store the sun's heat.

But even now, even as the afternoon temperatures climb higher for the next few days, we are already headed for a rendezvous with darkness and cold. Even on this longest day of the year, the twilight approaches. These long afternoons will grow shorter until the evening meal is surrounded by darkness. The lower sun will lengthen shadows; bright sunlight will evolve into an annoying glare. The nights will become as long as this day. Six months from now, in deepest, dark December, the sun will halt its southward dip and head north again, a simple phenomenon of planetary physics, a fact of living on a planet whose axis is tilted 23 degrees.

This summer solstice marks the day when Earth's axis leans farthest toward to sun; the winter solstice is the day that axis points farthest away. On this day, we celebrate the longest daylight of the year and head, inexorably toward the twilight.