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'Right in that sweet spot': Rarity of Aug. 21 total solar eclipse can't be overstated

Julian Gabel, 13, and Leah Font-Gabel, children of Creighton physics professor Jack Gabel, PhD, model special shades for viewing the sun in anticipation of the Aug. 21 total solar eclipse.Just as there is every 28 days, there was a full moon the night of Aug. 7.

But for all the folkloric portents associated with these monthly lunar events, this one actually heralds a monumental celestial event.

“Just think of it — we are now in the last cycle of phases of the moon before a solar eclipse,” said Jack Gabel, BS’94, PhD, a Creighton University associate professor of physics, who delivered a talk Aug. 7 about the upcoming Aug. 21 total solar eclipse that will cut a swath across the continental United States — the first to do so in 99 years. “All the conditions are set. It’s now a matter of waiting two weeks for the event itself and getting to feel like a little part of a huge piece of nature.”

A capacity crowd of more than 350 people filled the Rigge Science Building’s largest lecture hall for Gabel’s talk, which highlighted the astronomy of the eclipse, fun and helpful facts about other solar eclipses, the rarity of such events and safety precautions to take when viewing the event.

Touted as “The Great American Eclipse,” the Aug. 21 event has created a sensation in the U.S., not just among scientists like Gabel, but for people living in the path of the eclipse’s totality — a roughly 70-mile-wide band across which the moon’s shadow will streak, from Oregon to South Carolina, in a matter of 90 minutes — and others hoping to get into that path for a once-in-a-lifetime experience.

“If you’re able to find a way into the path of totality, I’d say it would be a good idea to try that,” said Gabel who, with the Creighton Department of Physics, will be leading an outreach event with about 600 area middle schoolers to view the eclipse near Tecumseh. “Even in Omaha it’s going to be a really thrilling, exciting thing — the sun will be just a small sliver here. But if you can get into that 70-mile band of the moon’s umbral shadow, it will be striking to see the sun completely blocked out and the ghostly streams of coronal light emanating from the dark hole where the sun should be.”

What makes seeing a total solar eclipse so rare, Gabel said, is the sheer accidents of physics and astronomy. Given we experience full moons and new moons roughly every month, one might think we’d experience solar eclipses just as regularly.

Solar eclipses of a non-total nature do happen twice a year, but they usually don’t last long and the moon’s placement between the sun and the earth doesn’t allow for the total darkness a total solar eclipse brings. Total solar eclipses also happen every year or two, but are visible for just a few brief moments over a very small region of the earth, often in remote areas or over open ocean where they go almost wholly unobserved.

Gabel said between the celestial conditions, the vastness of the earth and the timing of the event, the rarity of a total solar eclipse cannot be overstated. That one is going to cut across a sizeable chunk of inhabited land makes the Aug. 21 eclipse that much more special, he said.

For historical context, it was 1954 the last time a total solar eclipse was viewable from any spot in Nebraska. The next time a total solar eclipse will be viewable from anywhere in the state will be 2106 and the next time a total solar eclipse will be viewable from Omaha, the year will be 2245 — 228 years from now.

Add to that the ever-so-slight 5-degree tilt of the moon’s orbit around the earth, the relative sizes of the celestial bodies involved and their relative positioning to one another, a total eclipse is among the unlikeliest of happenings.

“If the moon was any closer to us, eclipses would be visible much more frequently,” he said. “If it was just a little further away, we’d never get them. The relative distances and sizes of the moon and sun are right in that sweet spot where the sun is completely blocked out for just a few fleeting moments over a small area of the earth. With the one coming up, that special place will sweep through Nebraska. Most of us will likely never have the chance to see an event like this again.”

The last total solar eclipse to cut across the U.S. occurred June 8, 1918, following a path from Washington to Florida. A year later, British scientists working off the coast of West Africa used a total solar eclipse there to help prove Albert Einstein’s theory of general relativity, measuring the bend in the light of visible stars around a massive object — in this case, the sun.

“So eclipses have helped advance science,” Gabel said. “The detectable bending of starlight was a dramatic confirmation of Einstein’s revolutionary theory.”

The view of the Aug. 21 eclipse over Nebraska will begin around 11:30 a.m., Central Daylight Time, when the moon will begin crossing between the sun and the earth, taking what appears to be a little bite out of our nearest star. The moon will gradually occult more of the sun until about 1:03 p.m., CDT, when, in the path of totality, the eclipse will last for up to two and a half minutes. In the path of totality, the darkness should be deep enough to see stars, notably the bright star Regulus, near the sun in the constellation Leo.

Special eclipse-viewing glasses will be needed to view the event, lest eclipse watchers do permanent, serious damage to their eyes. Only in its brief moments of totality can the eclipse be viewed safely without the special glasses. Gabel’s family handed out a pair of the special glasses to all in attendance at the Aug. 7 talk.

At several points throughout his talk, Gabel emphasized the importance of safety in viewing the eclipse. Photography and telescopic viewing must also take place through special, heavily-darkened lenses, he added. The only thing that should be visible through such lenses, Gabel said, is the sun.

“There is a very real potential to do permanent damage to your eyesight if you don’t take the proper precautions,” Gabel said. “It’s very simple. Except for those brief two-and-a-half minutes or less during totality, you must keep the shades on.”

In Omaha, Gabel said, since the eclipse won’t reach totality but will get to about 98 percent occlusion, anyone looking skyward for the event must keep the special lenses on during the entirety of the eclipse.

Other safe viewing options include creating indirect eclipse observation apparatuses, which can be as simple as looking at the light the eclipse casts on the ground through a hole in a piece of cardboard or through interlaced fingers. Gabel has posted more on the eclipse and safe viewing techniques at the Department of Physics website.

Gabel said this will be the first total solar eclipse he’s ever experienced and he’s looking forward to witnessing it with the middle-school students in Tecumseh, in the path of totality.

“There are really two ways to look at it,” Gabel said. “The first is the earth-to-the-sky event that we’ll all have a vantage point on. But the second is to think of the big picture. That our average star, the sun, in our average galaxy, is going to be blotted out by the smallest, closest thing to our planet, the moon. These are events that people look forward to for decades, but in the big picture out there, it’s just a blip. On earth, though, it is going to be something to behold.”

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