How long does a total eclipse last? According to Sperling’s “8-Second Law”, ALL Total Solar Eclipses Last 8 Seconds!
©1980 Norman Sperling.
Excerpted from What Your Astronomy Textbook Won’t Tell You, 0-913399-04-3.
First published in Astronomy magazine, vol. 8, no. 8, August 1980, 24-25.
Everyone who sees a total solar eclipse remembers it forever. It overwhelms the senses … and the soul as well – the curdling doom of the onrushing umbra, the otherworldly pink prominences, the ethereal pearly corona. And, incredibly soon, totality terminates.
Then it hits you: “That was supposed to last a few minutes – but that couldn’t have been true. It only seemed to last 8 seconds!”
This effect frustrated my first four eclipses, and most fellow eclipse fanatics assure me they’ve been bothered by it, too. Yet tape recordings, videos, and the whole edifice of celestial mechanics all claim that it did last the full, advertised two to seven minutes – to within a few seconds, that’s what really happened.
Where did all that precious time get lost?
True eclipse freaks recognize only two modes of life: eclipse expeditions, and preparing for them. They’ll devote a year or two to perfecting equipment: telescope, camera, weird filters and film; sandproofed, soundproofed, rainproofed (heaven forbid!), and bug resistant. No matter what their expedition sees or does along the way, they’ll fret about totality. Will the clouds part? Will * the * equipment * work? WILL * WE * SEE * IT?
The partial eclipse is a tantalizing, exasperating hour and a half. Then the diamond ring forms, gleams and vanishes – and at last they have totality. They gape in awe for just a second, then dive desperately into the sequence, many times rehearsed, of exposures, adjustments, notations so hurried they can only be unraveled from the tape recordings afterwards.
Inevitably, totality terminates too soon, often even before the planned sequence does, and they never make it to their own hard-won free-looking phase. “But I got it on film!” they proclaim, “And I can frame that and glow at it forever – even though … I only saw it … through the … camera’s finder.”
The novice and the non-astrophotographer take the hang-loose approach. Restless in the partial phase, they get impatient and even quarrelsome around the one-hour mark. But in the last 10 minutes they can feel it: totality’s a-comin’. The world is darker, oranger; shadows look oddly sharp-edged. There’s a nip in the air, the birds are atwitter, and shadow bands go skittering around. The ominous umbra sweeps in, the corona unfolds, the diamond glitters and is extinguished, and “OH * MY * GOD * THAT’S * THE * MOST * BEAUTIFUL * THING * I’VE * EVER * SEEN!” They stare transfixed, all their senses open, trying to take in as much as they can.
Unwilling to concede that totality can’t linger past third contact, they keep staring at the emerging solar sliver long after it gets painfully bright. Finally, they must be ordered to look away. Then, limp, with self-satisfied grins, they applaud, or yelp, or shuffle aimlessly and ask where the next one’s gonna be and how to get there.
Both styles of eclipse-watching yield the viewer a solid 8 seconds of memory. I replayed all my mental images of my first four totalities in about half a minute. And that was after seeing twelve and a half minutes of totalities. The other twelve minutes just weren’t there! Poof!
The culprit is attention span. If you stare transfixed, your mind, knowing the scene isn’t changing, says “I already know that”, and refuses to store away the same image yet again.
So the solution is not to stare.
What? Not look at that most marvelous miracle you’ve traveled umpteen thousand kilometers to see?
No, I didn’t say not to look, I said not to stare.
Pre-record a cassette, timed to start at the first diamond ring. On it, tell yourself what to notice during different parts of your precious few minutes in the Moon’s shadow. Notice how the umbra envelopes you, enjoy the diamond ring, then examine the prominences (they’re bright, so you don’t have to be fully dark-adapted). Next, survey the corona – its general shape, and any outstanding features.
Switch away for a few seconds, to check the colors all 360° around the horizon. Since totality is just starting, it’ll be darkest in the west, lighter in the east. Now back to the Sun. Your eyes, now partly dark-adapted, are ready for the corona. Which is the very longest streamer, and how far out can you trace it? Where is the innermost dark wedge? Pick out an interesting pattern of filaments and make a mental engraving of it.
OK, back to the horizon. Sweep around again, and notice how much difference a minute or two makes. The west is lightening, foretelling totality’s end, and the east is dark, where folks down-path are just now getting theirs.
Finally, back to the Sun. Review the best coronal details. Look again at prominences, since there’s a whole different crop of them on the third-contact side. Watch for the pink fringe of chromosphere that anticipates – yes, here it comes – the second diamond ring.
How quickly the corona fades! – and now, even the last of it is going – and it’s incredible how bright even that tiny wedge of Sun’s surface can be!
And now this eclipse, too, is over. But this time you’ve won. From each separate span of attention during totality you can savor your 8 seconds of mental replay. If you moved your attention enough times, you’ll recall many times that 8-second limit. Yes, Sperling’s 8-Second Law can be beaten!