Q: For the past few weeks I’ve heard everybody yapping eclipse this and eclipse that. The moon passes in front of the sun. Big deal. Tell me, oh great Answer Man, does it really make any difference?
C.P., of Mascoutah
A: As a matter of fact, it can, oh dubious party pooper. We’ve come a long way from the days when terrified primitive societies banged drums and shook rattles to scare off the evil monsters that were suddenly devouring the sun at midday. Far from a biblical omen of doomsday (Amos 8:9, among others), this simple yet awe-inspiring alignment of earth, moon and sun has produced several discoveries that have helped reshape our scientific knowledge. As early as 500 B.C., the Greek philosopher Anaxagoras used eclipses to conclude that the sun had to be farther away from Earth than the moon, but let me give you two more recent examples.
While observing the solar eclipse of Aug. 18, 1868, French astronomer Jules Janssen noticed several bright lines in his spectrograph of the chromosphere, which is the middle layer of the sun’s atmosphere. To him, this proved the chromosphere was gaseous.
Never miss a local story.
More important, though, one of these lines was a bright yellow marker never seen before that scientists thought might indicate the existence of an element not yet found on Earth. Sure enough, two months later British astronomer Joseph Lockyer observed the same yellow line. After several years of follow-up lab work, he and his team concluded that it was indeed a new element. They named it “helium” after the Greek word for the sun (helios), and it became the first element discovered in space before it was finally confirmed on Earth — in 1895.
If that’s not earth-shattering enough for you, consider this: In his 1915 general theory of relativity, Albert Einstein predicted that the sun’s gravity distorts spacetime in its vicinity. In other words, if you’re looking at stars behind the sun, they would appear to be in different positions with respect to each other during an eclipse than they would during a normal night when the sun wasn’t there. The warping of spacetime near the sun bends the light rays from the stars, he hypothesized.
At the time, the theory was just so many words. But during a total solar eclipse on May 29, 1919, British astronomer Arthur Eddington took photographs that proved Einstein was right on the money.
“Lights all askew in the heavens,” the New York Times trumpeted in its headline on Nov. 9 to top one of the most revolutionary science stories ever published. “Men of science more or less agog over results of eclipse observations.”
On Monday, scientists ranging from professional physicists to amateur astronomers with do-it-yourself equipment will try to refine those 1919 findings even further. And that’s just the start of what they’ll be doing:
The eclipse will allow further work on the question of why the corona, a band of plasma that surrounds the sun, is so much hotter than the sun itself. In fact, it’s not even close. While the sun’s visible surface is just 5,000 degrees, the corona is more than a million. Is it, like your microwave oven, caused by waves coming out of the sun’s magnetic field and heating the plasma? Or is the corona filled with “nanoflares,” countless and continuous tiny explosions too small for eye to see? Scientists hope the dimming of the sun will help shed more light on the answer.
Scientists also will be studying the effects of the eclipse on the ionosphere, part of our own planet’s upper atmosphere. During the daytime, this region is highly charged when extreme ultraviolet photons from the sun bombard the ionosphere to produce free electrons and ions. At night after the sun sets, this charge is greatly reduced. During an eclipse, the ionosphere is switched off and on relatively quickly, creating an ideal situation to learn more about how such changes affect radio-wave communication here on Earth and with our satellites in space. It may also help us gain a better grasp on predicting the effects of space weather conditions on communication.
Some experiments won’t focus on the sun, moon or Earth at all. While flying around during the eclipse, scientists also will study Mercury, the planet closest to the sun, to try to figure out what its surface is made of. Measuring how quickly the planet loses heat can help researchers determine its subsurface. If it holds heat longer, it’s probably packed rock; if it loses heat relative quickly, it’s more likely looser soil or sand.
I hope this shows that while you can choose to ignore the eclipse as a celestial beauty pageant, scientists will be hard at work trying to rock your universe.
▪ Don’t forget: Whether you missed the experience or want to relive it, don’t miss “NOVA: Eclipse Over America” at 9 p.m. Monday on KETC-TV. Just hours after the event, NOVA will show not only footage of the eclipse from throughout the country but also discuss how scientists I’ve just discussed use eclipses to further our knowledge. The show will be repeated at 8 p.m. Wednesday.
In addition, the St. Louis Science Center will help you get ready for the big event with a full day of activities from 9:30 a.m. to 4:30 p.m. Sunday followed by an eclipse watch celebration from10 a.m. to 3 p.m. Monday at the McDonnell Planetarium. A ticket to the Planetarium show will get you a free pair of solar glasses. (Sorry, the gift shop is sold out.)
What famous scientist is thought to be the first person to ever witness a solar eclipse while flying? Eclipse Eve Bonus: When was the first known picture of a total solar eclipse taken?
Answer to Saturday’s trivia: On Dec. 9, 1683, Harvard College (established in 1635) announced that its annual commencement would be held July 2, 1684. Four days later, they realized that that would be the day of a total solar eclipse visible on Martha’s Vineyard. Not wanting to miss such a rare celestial event, Harvard President John Rogers and two Fellows wrote Increase Mather for permission to move the ceremony back one day. “Wee (sic) are not superstitious about (the eclipse), but reckon it very inconvenient.” The request was granted, and commencement went off without a hitch. So did the eclipse — with one macabre twist: While residents turned their attention to the skies on the afternoon of July 2, President Rogers died suddenly because of a “visitation of sickness.” Maybe he shouldn’t have messed around with Mother Nature.