For less than two minutes on August 21, stargazers across the United States will ignore everything they’ve been taught and try to look directly at the sun.
In what the science community is calling the astronomical event of the decade, a total solar eclipse will cross through the middle of the country.
A solar eclipse occurs when the moon’s orbit comes between the path of the Earth and the sun. Solar eclipses themselves are not rare, but a visible total solar eclipse across the continental United States has not happened in 99 years.
“The moon is way, way smaller than the sun — about 400 times smaller across than the sun and about 400 times closer than the sun,” says Geneviève de Messières, an astronomy education program manager at the National Air and Space Museum in Washington. In a total solar eclipse, “the moon is at just the right distance to cover the sun.”
At least two total eclipses happen on Earth every year, but they pass mainly over stretches of ocean. The upcoming eclipse is highly unusual because many people living in the United States will be a few hours’ drive from the path of totality.
This path, a ribbon stretching in length from Oregon to South Carolina but only 70 miles wide, will be the only area to experience the full blockage of the sun.
The eclipse itself will last a few hours, but during its peak, which will last about two minutes or less in a given location, the daytime sky will suddenly turn dark and have the brightness of a full moon. Only the sun’s corona, or glowing outer atmosphere, will be visible.
In other parts of the country, including the Washington area, you can see a partial eclipse. In these areas, you will see the sun obscured into a crescentlike shape during the day.
To watch an eclipse, you need to protect your eyes. Looking directly at a partial eclipse could burn the eye, causing permanent damage. Only during peak time in the path of totality will you be able to safely look directly at the sun.
Otherwise you will need protective eyewear, such as eclipse glasses, to view the eclipse. Many companies sell them, but NASA has a guide with recommendations at eclipse2017.nasa.gov/safety.
It’s also possible to watch the eclipse by using a projection method. There are several methods, and astronomers are telling people to be creative.
You can use a hole punched through paper to project the movements onto a white sheet of paper, a wall or the sidewalk. You can watch the shadows cast by tree leaves. Even a pasta strainer can become a solar projector. Find instructions for these suggestions at eclipse.aas.org/eye-safety/projection.
Although astronomers are preaching about eye safety and warning of clouds potentially affecting your view, they are pausing to geek out and enjoy the significance of the moment.
“This is one of the rare times I get to see something that we normally have to build multimillion-dollar spacecrafts to see with your own eyes,” says Smithsonian astrophysicist Kelly Korreck.
“We all get a chance to connect with our solar system and with our universe in a way that’s unprecedented,” says C. Alex Young, NASA’s associate director for science. “I get to have this collective experience and this cosmic awareness with so many people across that day.”