Nine years ago today, on 21 August 2017, a shadow about 115 kilometres wide came ashore in Oregon and left the country in South Carolina roughly ninety minutes later. The first total eclipse to cross the contiguous United States since 1918, and the whole thing rests on a coincidence I still find faintly ridiculous: the Moon is about 400 times smaller than the Sun and happens to sit about 400 times closer, so the two discs come out almost exactly the same size in our sky. A wristwatch face held at arm's length can hide a distant building. That is the entire trick.

The umbra crossed the ground at something like 3,800 kilometres per hour on the Oregon coast, slowing to roughly 2,400 in the middle of the country — geometry, not weather. Nobody outruns it. And where the shadow was deepest, near southern Illinois, totality lasted about two minutes and forty seconds. Not long. Long enough for the temperature to drop, for the crickets to get confused, and for a lot of otherwise composed adults to make undignified noises.

In the first photograph below, that single brilliant burst at the upper right is the last sliver of sunlight through a valley on the Moon's edge, with the corona already glowing around the rim. The NASA map below it shows the whole diagonal march, Oregon at 10:10 in the morning to South Carolina by 2:50 in the afternoon. Look up sometime — with proper filters if the Sun's involved!