Preparations have already begun for what scientists are calling the Great American Eclipse of 2017. For the first time in American history, on August 21, 2017 the "path of totality" of a solar eclipse—that is, the path along which the Moon's shadow transits—will run exclusively and entirely across U.S. soil in a 70-mile-wide line running from Oregon to South Carolina. Astronomers see it as an opportunity for new scientific observations and public engagement.
The last coast-to-coast solar eclipse over North America occurred in 1918. It followed a similar path as the 2017 eclipse, but because its path also brought it over Bermuda—then part of the British Empire, now a British territory—the United States couldn't claim exclusivity. The 2017 eclipse won't pass over Bermuda or any other territory. It is truly "all American."
"The is the science Super Bowl," said physicist Angela Des Jardins of the Montana Space Grant Consortium, who is leading an experiment in which 50 teams of students in 30 states will fly high-altitude balloons during the eclipse. Speaking on June 2 at the 47th annual conference of the Solar Physics Division of the American Astronomical Society in Boulder, Colorado, she described how the balloons will transmit to the Earth's surface live video from the edge of space. Only once has an eclipse ever been observed from such a height—over Australia, in 2012—though coverage and images were then limited. "There's never been live footage from the edge of space, and certainly not coverage across an entire continent," she said. "It's going to be awesome."
Scientists anticipate filling other gaps in our understanding of the Sun as well. According to astronomer Shadia Habbal of the University of Hawaii, the eclipse will provide to scientists "unsurpassed views of the physics of the solar corona," the halo of plasma surrounding the Sun that burns at 1,000,000 degrees Kelvin. During the eclipse, when the Sun is blotted out, instruments will be able to observe the intricate details of coronal structures, register the escape of material from the Sun, and capture plasma instabilities otherwise too faint to observe. "The solar corona is a rich astronomical laboratory we can observe in exquisite detail," Habbal noted.
ENGAGING—AND EDUCATING—THE PUBLIC
In 2014, the National Science Foundation mounted a study that it repeats every few years, in which it tests scientific literacy by asking Americans whether the Earth goes around the Sun, or the Sun goes around Earth. This question was settled in the 17th century, but apparently word hasn't yet reached everyone: 26 percent of the American public thinks the Sun orbits the Earth. ("We hope to decrease this percentage by a little bit," said Des Jardins.) If for no other reason, then, scientists hope the eclipse will spur people to look up and consider the solar system, how it works, and our place in it.
Jay Pasachoff, a professor at Williams College and the astronomy equivalent of Indiana Jones, travels the world to study eclipses. He has observed 63 of them. He wants the public to travel to the path of totality and be active participants in the 2017 eclipse. "We want to let you know in advance that you will be missing some really wonderful stuff if you are not in the zone of totality on August 21," he said at the conference. (Previously, he described witnessing an eclipse outside of the path "like going up to the ticket booth of a baseball or football stadium but not going inside.")
To view the eclipse for its maximum duration, observers will have to travel to Hopkinsville, Kentucky. There, the eclipse can be experienced for a full two minutes, 40 seconds, during which time it will become as "dark as night in the middle of the day," according to Pasachoff. The town has been preparing for the event for several years, building accommodations for a large influx of visitors, who are expected to number in the hundreds of thousands. A dress rehearsal of sorts was held in June 2012, when thousands flocked there to view the transit of Venus.
There are other vantages along the continental path, however, that offer shorter viewings but unique experiences. In Kentucky alone, one can forego Hopkinsville and instead choose Bowling Green, where the totality of the eclipse will be shorter but the Sun's reddish chromosphere will be more visible. Elsewhere in the country, many are expected to climb mountains and not only witness the eclipse above, but also look down and watch as the moon's shadow crawls eerily across the ground below.
All of this, of course, depends on clear skies. "You can't outrun the clouds, so hope for good weather," said Pasachoff. But even if unfavorable weather obscures the event, there will still be a creepy darkening of the skies to be enjoyed. Meanwhile, NASA's website, and others, will be broadcasting the event. In the worst-case scenario, the wait won't be terribly long for the next solar eclipse—just seven years. On April 8, 2024, the path of totality of a solar eclipse will cross from Mexico to Newfoundland, passing over much of the central-eastern U.S. in the process.