Thanks to Iris.
A Total Solar Eclipse Feels Really, Really Weird
Bob Berman, Wired, Aug. 8, 2017
Have you ever witnessed a total solar eclipse? Usually when I give a lecture, only a couple of people in an audience of several hundred people raise their hands when I ask that question. A few others respond tentatively, saying, “I think I saw one.” That’s like a woman saying, “I think I once gave birth.”
What these people are remembering is some long-ago partial solar eclipse. These are quite common. They occur every few years in various places across the globe. But believe me, if you’ve seen a total solar eclipse—when the moon passes directly between the sun and the earth—you’ll never forget it.
Part of what makes a total eclipse so breathtaking has to do with invisible light. During the “moment of totality”—the minutes when sun is completely blocked—observers experience the exquisitely odd and wondrous sensation of solar emissions, both visible and invisible, vanishing right in the middle of the day.
You have a chance to experience this firsthand. The United States has reached the end of the longest total-solar-eclipse drought in its history. A total solar eclipse—or totality—has not been observed from anywhere in the mainland United States since February 26, 1979. This bizarre thirty-eight-year hiatus ends on August 21, 2017, when a coast-to-coast totality sweeps across the continent, ramping up an eclipse fever that is already highly publicized.
For those who do not live in or travel to the narrow, ribbon- like path of totality—the area from which the sun will appear to be in total eclipse, which stretches from the Pacific Northwest to the Carolina coast but is about 70 miles wide – a second totality will unfold on April 8, 2024. Two in a mere seven-year period.
Then, as if to compensate for the scarcity of these events (even the 1979 eclipse was a mostly cloudy, far-northern event only observable in a few places such as Helena, Montana), the middle and late parts of the twenty-first century will offer a second sudden flurry of them.
In any given place on earth, a totality appears just once every 375 years. If it’s cloudy, you have to wait another 375 years. So a totality is a very rare event for any location. But that interval of time is just the average. Here and there, a few places will enjoy two totalities in a single decade: Carbondale, Illinois, for example, sits at the intersection of both eclipse tracks—2017’s and 2024’s. Yet residents of other cities, including Los Angeles, must cool their heels for more than a millennium.
In the United States, no major urban center has seen a total solar eclipse since the dual events of Southern California in 1923 and the now-famous New York City totality of 1924. Boston was scheduled for a sunrise totality in October of 1925, but it was cloudy.
Every eclipse path—a map of the places on earth from which the sun is completely blocked and where stars are seen during the day—is long and narrow. During that Roaring Twenties Big Apple eclipse, for example, the totality ran from central Canada southeast to Albany, in upstate New York, then down through the Bronx and Harlem, and ended unceremoniously at 86th Street in Manhattan, near an eatery that would someday be famous for hot dogs and papaya drinks. People south of the subway stop there stood in daylight: no stars out, no mind-numbing glimpse of the solar corona, no hot-pink flares shooting from the sun’s edge. Volunteers were dispatched to each street so scientists could later know the precise location of the edge of the moon’s shadow. The next day, a newspaper writer, watching the disappearing sun’s final dazzling pinpoint, described it as a diamond ring—a term that has since been fully incorporated into eclipse-speak.
The event has an indescribable effect on observers. While most experienced astronomers would concede that a total solar eclipse is the most powerful, gorgeous, and even life-altering of all celestial phenomena, they’d rate a vivid display of the northern lights as not too shabby, either. A big gap separates those two from the rest of what I call the top four natural spectacles, including a rare brilliant comet and a meteor storm, in which more than a dozen shooting stars flash across the sky each minute. Like the aurora borealis, a solar totality often invokes involuntary gasps and cries of wonder. You’ll often hear that some kind of “feeling” accompanies the visual spectacle. Perhaps this has to do with the fact that both these events are indeed accompanied by large changes in the amount of incoming electromagnetic radiation. It should also be noted that lunar eclipses, even total ones, do not make this top-four list. Those fairly commonplace eclipses, which unfold every few years and are never limited to a narrow section of our planet but instead are visible to half the world, are certainly pretty and worth watching. But they are not life-altering.
In just another few hundred million years, total solar eclipses will be over forever.
During a solar totality, animals usually fall silent. People howl and weep. Flames of nuclear fire visibly erupt like geysers from the sun’s edge. Shimmering dark lines cover the ground. In both the 2017 and the 2024 events, the entirety of the United States and Canada will experience a partial eclipse, so that anyone using protective eyewear will be able to see it by standing outside or by looking out a window (provided that it’s not cloudy, of course). In contrast, less than 1 percent of the continent will experience totality. To most people, it might seem that seeing a partial eclipse ought to be almost as good as seeing a total eclipse, and it’s certainly a lot more convenient. Why travel? The sun being 99.9 percent eclipsed doesn’t sound too different from its being 100 percent eclipsed, right?
Actually, seeing an almost total eclipse is no better than almost falling in love or almost visiting the Grand Canyon. Only full totality produces the astonishing and absolutely singular phenomenon that resembles nothing else in our lives, on our planet, or in the known universe.
No discussion of totality should omit the strange science lurking behind it. It starts with a bizarre coincidence: the moon is four hundred times smaller than the sun, but it also floats four hundred times nearer to us. This makes the two disks in our sky appear to be the same size. Now, if the moon appeared larger than the sun, it could still occasionally stand in front of it, but it would also blot out the dramatic prominences along the sun’s edge, those geysers of pink nuclear flame. So for maximum amazingness, these bodies must have identical angular diameters—i.e., they must appear to be the same size. And they do.
The moon wasn’t always where it is now, which makes the coincidence even more special. The moon has really just arrived at the “sweet spot.” It’s been departing from us ever since its creation four billion years ago, after we were whacked by a Mars-size body that sent white-hot debris arcing into the sky. Spiraling away at the rate of one and a half inches per year, the moon is only now at the correct distance from our planet to make total solar eclipses possible. In just another few hundred million years, total solar eclipses will be over forever.
About the author
Bob Berman is one of America’s top astronomy writers, and the author of Zoom: How Everything Moves and The Sun’s Heartbeat. He is a columnist for Astronomy and the science editor of The Old Farmer’s Almanac.