In less than a year, professional astronomers, amateur sky gazers and inexpert laypeople will gather across the country to experience what some consider one of nature’s most breathtaking phenomena. It marks a singular moment in time when analytical meets spiritual, a convergence of logic and emotion. It is the type of event that can elicit tears from the most hardened observer, unbridled shouts of joy from the most passive participant and instant bonding between people of all backgrounds and beliefs. This miracle of the heavens is a total solar eclipse, and it will be visible on Aug. 21, 2017, from a 70-mile-wide band, stretching across the United States.
An Emotional Experience
For centuries, scientists have taken advantage of the special circumstances of total solar eclipses to learn about our solar system. More than 2,100 years ago, the ancient Greek astronomer Hipparchus compared observations of such an eclipse made from different spots to calculate the distance between the Moon and Earth. His estimate of 268,000 miles is within about 11 percent of the actual distance, not bad considering the archaic observing techniques of the time.
More famously, in 1919, British astronomer Arthur Eddington traveled to an island in the Pacific to photograph stars around an eclipsed Sun. Albert Einstein had predicted in his general theory of relativity that starlight would not travel in a straight line but instead bend slightly as it passed by an object, whose gravity would tug on the starlight. Eddington saw a perfect opportunity to test this prediction by observing and measuring starlight as it passed by the darkened Sun during a total eclipse. Eddington’s findings seemed to support Einstein’s prediction (later astronomers have debated the accuracy of Eddington’s measurements) and made Einstein an instant global celebrity.
While these and other total solar eclipse observations have provided fodder for fundamental research, none of them seems to match the emotional value of observing such an event. Part of this is because of the rarity of such events, part is because anyone on Earth in the right location can observe totality without any special equipment. But more poignant reason relates to the distinct conditions that separate a partial eclipse from a total one. Comparing the two is literally the difference between day and night.
During totality, an eerie darkness sets in, confused animals come out, planets and stars become instantly visible, and any winds tend to diminish. Lowell Observatory Director Jeff Hall remembers observing the one on March 7, 1970, as a five-year-old boy in Virginia.
“I can dimly view the scene in my mind’s eye in front of this little house,” he said. “The two things that I thought were most striking were: it got cold, just like that, out of nowhere; and then all of the nocturnal animals started chirping. It was a deeply affecting experience and you can easily see why the ancient people and astrologers regarded these kinds of things as either fundamental or catastrophic.”
This proved to be an influential event in Hall’s life, and he identified it as one of a handful of key factors that inspired him to become a scientist.
Hall also recalled another eclipse, the 2012 ring-shaped one visible from Northern Arizona. He was at Wupatki National Monument, where an estimated 1,500 people swarmed the site. Hall gave a program in the ancient community room while others set up telescopes around the property to view the eclipse.
While this event did not necessarily trigger the senses as much as it may have had it been a total eclipse, it still evoked an emotional response because of the heritage of the location.
“Giving a talk about eclipses in the community room, with people sitting along the walls, it was like being transported back a thousand years because I’m sure at some point something interesting happened in the sky back then and the ancient people were sitting there doing the exact same thing, marveling at what was going on. It just created this tremendous connection to the past and the history of what’s transpired there,” he said. “That’s the kind of thing that these singular astronomical events do, they just give you those moments.”
These two experiences intrigued Hall as both a scientist and human, and serve as examples of why people plan, sometimes years in advance, for what often becomes a pilgrimage for truth and a connection to the natural world.
The Nature of a Total Solar Eclipse
Solar eclipses, like those of the lunar variety, happen as a result of the interplay between Earth, the Moon and the Sun. Each month, as the Moon orbits Earth, it passes directly between our planet and the Sun – a time recognized as the phase of the new moon. If the three bodies were lined up precisely, we could theoretically see a solar eclipse at each new moon phase as a result of the Moon blocking the Sun from our view. But the Moon orbits Earth at a slight angle, so that the three bodies line up only two to five times per year. In the majority of cases, the positioning is still not perfect and only part of the Sun is blocked from our view, resulting in a partial solar eclipse – one of three types of solar eclipses.
The second and third types of eclipses not only require that the bodies all line up just so, but also depend on the distance between the Earth and Moon, which fluctuates throughout the year. When the Moon is at its more distant position, it will not completely cover the Sun, resulting in an annular eclipse (as Arizona witnessed in 2012), in which a ring of sunlight is still visible. When the Moon is close enough, it will completely block the Sun and create a total solar eclipse.
Total solar eclipses also are possible thanks to a cosmic quirk of timing; the Sun is about 400 times larger than the Moon, but we happen to live during a time when it is also 400 times further away from Earth than the Moon. The Moon is creeping away from Earth at a rate of about one inch per year, and eventually – thousands of years in the future – it will be far enough away that its smaller apparent size will not completely block the Sun and humans will no longer experience total solar eclipses.
On average, total solar eclipses occur once every 18 months. But the path from which such events are visible is narrow and varies with each eclipse, so total solar eclipses cross the same geographical area on Earth only about once every 375 years. Arizona is in the middle of a 399-year wait; it hasn’t witnessed a total solar eclipse since Thomas Jefferson was president in 1806 and will have to wait until 2205 to see the next one (for the 2017 event, as explained below, the Sun will only be partially eclipsed as seen from Arizona).
The last total solar eclipse to cross into United States territory was in 1991, when a July 11 event was visible from Hawaii. The last one seen from the continental United States fell on Feb. 26, 1979, but the last one to stretch across the entire country – like the 2017 version – happened on June 8, 1918. The next one visible from the United States will be in 2024, when the path of visibility will stretch in a northeasterly direction from Texas through Maine. Not until 2045 will another total solar eclipse cross the continent from the Pacific to Atlantic oceans.
The path of totality for the 2017 eclipse stretches from Oregon in a southwestern direction to South Carolina.
From Flagstaff, the Sun will still be partially eclipsed, with 70 percent of the Sun covered. Lowell Observatory astronomers, educators, volunteers and support staff will travel to Madras, Oregon, which is right in the middle of the path of totality. Lowell has reserved the Madras High School football field and adjacent performing arts center for several days of public star parties, programming and, of course, eclipse viewing. It will be an opportunity to learn, but as importantly, to experience one of nature’s most striking displays of grandeur.
The last total solar eclipse to cross into United States territory was in 1991, when a July 11 event was visible from Hawaii. The last one seen from the continental United States occurred on February 26, 1979 but the last one to stretch across the entire country—like the 2017 version—happened on June 8, 1918. The next one visible from the United States will be in 2024, when the path of totality will stretch in a northeasterly direction from Texas through Maine. Not until 2045 will another total solar eclipse cross the continent from the Pacific to Atlantic oceans.
The path of totality for the 2017 eclipse stretches from Oregon in a southwestern direction to South Carolina. While totality will not be visible from Arizona, observers in the state will still see an obvious partial eclipse.
From Prescott, the Sun will begin going into shadow at 9:12 a.m. At this time, it will be located to the east/southeast and about 40º above the eastern horizon (the width of your fist held at arm’s length is about 10º, so this will be four fist-widths off the horizon). By 10:32 a.m., the Sun will have risen about 55º above the eastern horizon and be 70 percent covered, marking the maximum stage of eclipse. It will then gradually come back out of the moon’s shadow until 11:59 a.m., when the eclipse ends.
The Aug. 11, 2017 event will be the only solar eclipse of any kind visible from Prescott until 2023. As for lunar eclipses, the next two visible from the area will be on Feb. 10, 2017 (partial) and Jan. 21, 2018 (total).
By Kevin Schinder, FBN
