Regardless of who is elected to the presidency next month, he or she won’t be able to screw up one of the great events of 2017: the Great American Solar Eclipse.

On August 21st, the new moon will pass, briefly, in front of the sun. Its shadow will come ashore near Portland, Oregon, and sweep across the country all the way to Charleston, South Carolina. It will be the first total solar eclipse visible in the lower forty-eight states since 1979. There will not be another until 2024. It will be visible from, or very near, several major cities: Portland, Omaha, Kansas City, St. Louis, Nashville, Chattanooga, Atlanta, and Charleston. The period of totality will reach its maximum just south of Carbondale, Illinois–two minutes and forty seconds. Curiously, the path of the 2024 eclipse will cross this one’s at virtually the same spot, giving that area two total eclipses in just eight years. The average wait between total solar eclipses at any given spot is about 375 years.

The total eclipse will only be visible from American territory, the first time that has happened since June 13th, 1257, more than half a millennium before the country even existed. (Yes, we can determine eclipses with astonishing accuracy from the distant past to the distant future. There will be a partial one on April 17th, 3009. The one on June 25th, 2522, will have a very long totality, seven minutes and twelve seconds. Save the dates.)

A total solar eclipse is, by at least an order of magnitude, the greatest predictable spectacle in all of nature. And the difference between seeing it yourself and seeing it on television is the difference between night and day. I would urge everyone not in jail to take advantage of this golden opportunity. I promise you, you will be utterly awestruck—in the fullest sense of that word—and remember it for the rest of your life. I know. I saw the total solar eclipse of March 7th, 1970, in a cloudless sky at the Norfolk, Virginia, airport.

It is, presumably, sheer coincidence that the apparent diameter of the moon is nearly the same as the sun. While the sun is about 400 times larger than the moon, it is also 400 times further away. A time will come when we won’t have total eclipses anymore. The moon is moving away from the earth at a rate of about one inch per year—and the rotation rate of the earth, to conserve the angular momentum of the earth-moon system, is slowing down commensurately. In several hundred million years, total eclipses will be no more.

To observe an eclipse, you need eclipse glasses (ordinary sunglasses will not do). Never, ever, look directly at the sun, except during totality, with your naked eyes. Severe retinal damage can result.

At first there is not much to see, just the disc of the moon slowly advancing across that of the sun, from lower right to upper left. As the sunlight slowly diminishes, your eyes adjust and you don’t notice much difference. But as totality approaches, the light, coming from just the limb of the sun, gets noticeably redder. Finally, with your eyes not able to adjust any further, the light will seem to drain from the sky, as though a giant rheostat were cranking it down. “Bailey’s beads” will briefly appear as the remaining sunlight pours through the mountains and valleys of the moon’s edge. And then, at the instant of totality, the sun’s corona—its glowing atmosphere—will burst across half the sky in a glory that cannot be imagined, it can only be experienced.

The stars come out, birds go silent, the breeze stops, the world stands still.  And then, Bailey’s beads reappear and totality is over. The world will slowly return to normal.

But you will not be quite the same person you were two minutes earlier.

solar eclipse
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