A total solar eclipse will stop millions of Americans in their tracks on Monday when it crosses the country from coast to coast, shrouding states in sudden darkness.
The rare celestial spectacle on Aug. 21 has a trajectory exclusive to the U.S. for the first time since the nation’s birth in 1776. It’s also the first total eclipse of the sun that will be visible from the contiguous U.S. since 1979.
As the once-in-a-lifetime event draws near, here are four things to know about the total solar eclipse:
You cannot race the 2017 total solar eclipse
Even the most dedicated eclipse chaser would not be able to keep up with the August eclipse as it makes its way across America. Someone would need to travel at roughly 2,400 mph to chase the moon’s shadow, according to Bill Kramer, a well-known expert in the eclipse chasing community. The upcoming eclipse first makes contact in Madras, Ore. at 9:06 a.m., PST reaching totality there at 10:19 a.m. Its path of totality ends near Columbia, S.C. at 2:44 p.m. EST, just about an hour and a half after the total eclipse began in Oregon. The total eclipse can be viewed widely in about 10 states, and totality typically lasts no longer than two minutes and 40 seconds.
Snake-like figures can emerge in the shadows
Mysterious shadowy figures that wriggle like snakes have been known to appear on surfaces near the ground seconds before and after a total solar eclipse. The shadow bands — sometimes called shadow snakes — are thin and wavy lines that can be seen moving on plain-colored surfaces, like white cars. The faint, squiggly figures fluctuate in lightness and darkness and do not always show during solar eclipses. “They look like ripples of sunshine at the bottom of a swimming pool,” NASA says on its website. Scientists have been stumped by the rare and unpredictable phenomenon for at least a century. However, NASA said the “simplest explanation” is that they likely arise from “atmospheric turbulence,” or how light passes through different layers of the atmosphere. Renowned English astronomer George Airy wrote about shadow bands during a total eclipse in the early 1840s, according to the space agency. “As the totality approached, a strange fluctuation of light was seen upon the walls and the ground, so striking that in some places children ran after it and tried to catch it with their hands,” Airy said.
It will be one of history’s most widely documented eclipses
Google and the University of California, Berkeley have teamed up to create a “mega-movie” about the 2017 total solar eclipse that stitches together thousands of images captured and submitted by the public along the path of totality. The team said the “first-of-its-kind citizen science project” aims to serve as a reminder of the historic moment and also help scientists study the sun’s corona. The goal is to compile a “unique treasure-trove of information on how the corona changes over time.” The data gathered will be made available publicly, although the team did not specify how it would be viewed. Meanwhile, NASA will send high-altitude balloons up into the air, from more than 50 locations within the path of totality, to observe and capture live images and videos. The space agency said the balloons would ascend to 100,000 feet above Earth and would burst shortly after the eclipse is over.
Total solar eclipses won’t be around forever
There will be no more total solar eclipses in about 600 million years, scientists say. Because of the moon’s slowly increasing orbit, NASA believes the moon will have moved far enough away from Earth in that timeframe that it will no longer be big enough to entirely cover the sun. “It will be too small in the sky,” said Dr. C. Alex Young, the associate director for science in the heliophysics science division at NASA’s Goddard Space Flight Center. The moon’s orbit is increasing by about 1.5 inches each year, Young added. The sun is also expected to expand slightly in the future but NASA has not yet seen a noticeable change, Young said. Partial eclipses will still exist in 600 million years.