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5 things you should remember as you prepare for the great solar eclipse

BY and   August 17, 2017 at 5:56 PM EDT  | Updated: Aug 19, 2017 at 8:13 PM

Few things ignite the collective imagination like a solar eclipse, and August 21 will be no exception. On that day, a total solar eclipse will sweep across the entire continental United States. Such a spectacle hasn’t happened since June 8, 1918, and anticipation couldn’t be higher.

Can’t find a pair of eclipse glasses? You can always build your own sun viewer with trash bags or a pasta colander.

Transportation officials are expecting clogged highways as a major portion of the 200 million who live within a day’s drive flock to the path of totality — the 70-mile-wide, 3,000-mile-long swath below the shadow of the moon. Both NASA scientists in jets and regular citizens in chartered planes will chase the moon, while Amtrak’s solar eclipse train sold out in less than 24 hours.

This hysteria is warranted. Though total solar eclipses happen frequently on Earth, once every 18 months, ones to cross the U.S. are much less common. The last cut through the Pacific Northwest in 1979, and the next will slice through the midwest in 2024.

But if you plan to join the 5,000-year-old tradition of eclipse watching next Monday, here are five things you need to remember.

1. You shouldn’t look at the eclipse, unless you live here

The luckiest among us will be able to stare at the eclipse without eye protection for a very brief period. But take note! This exposed viewing is only permissible for the totality — the 2.5 minutes when the moon completely obscures the sun. And this experience will only happen on the path of totality.

The rest of the country and the remainder of the 90-minute eclipse will be partial and should not be viewed without proper protection. Even a brief, unprotected exposure to sunlight can harm one’s eyes, so best to play it safe with a pair of eclipse glasses.

Example of eclipse times for cities in the path of totality. Chart by NASA

Example of eclipse times for cities in the path of totality. Chart by NASA

NASA and the American Astronomical Society recommend that people use eclipse glasses, camera filters and telescope viewers from “reputable vendors” that follow international safety standards. Such glasses and lenses carry the manufacturing number “ISO 12312-2” and make the sun look 100,000 weaker than normal.

Do not look at the solar eclipse through a large camera, a telescope or binoculars unless they have the proper filters, even if you are also wearing eclipse glasses. The concentrated light will burn through the glasses and damage your eyes.

But counterfeits abound. Last week, Amazon recalled a set of eclipse glasses, saying it was unable to confirm whether the protective ware was made by a recommended manufacturer. Also, don’t use glasses that are more than three years old, scratched or wrinkled. Protective gear is especially important for the developing eyes of children, who might be prone to incorrectly wearing the glasses.

So where should you go to get glasses? There are a number places handing out free, verified glasses for the event. Public libraries across the country will hand out more than 2 million pairs of compliant glasses, thanks to a donation from NASA, Google, and the Gordon and Betty Moore Foundation and the Space Science Institute. There’s even a map where you can find the nearest participating library. Warby Parker, the chic eyewear company, has been handing out free eclipse glasses since August 1.

Can’t find a pair of eclipse glasses? You can always build your own sun viewer with trash bags or a pasta colander. And there are many ways to stream the eclipse via the web.

2. The eclipse is a great time for experiments

A total eclipse is a ripe time for science. If not for the solar eclipse of 1868, we wouldn’t know about helium.

During the totality, Earth-based telescopes will obtain a better view of the sun’s corona — the ring of starlight left unobscured during the eclipse. These wisps of super hot plasma get washed out by the rest of the sun’s light emissions. But this dim ring can reveal details about the sun’s magnetic fields and the source of solar winds. Some astrophysicists will use the occasion to measure the sun’s diameter, while other will scan for geologic features on nearby Mercury. Indeed, the drop in light exposure on Earth will make the sky dark enough to see four other planets.

3. Animals get weird during an eclipse.

The California Academy of Sciences and the nature organization iNaturalist want spectators to look around, rather than up, during the totality and document any bizarre animal activity. Anecdotal reports acknowledge a bevy of oddball behaviors during past eclipses.

Bugs tend to lose their collective minds on the great day of shadow. Crickets chirp, assuming night has fallen. Cicadas in the southwest cease their calls, for the same reason. Bring the bug spray, because mosquitoes tend to emerge in greater numbers as the moon blocks out the sun.

Here’s why scientists are collecting accounts of strange animal behavior via citizen science websites like Video by Teresa L. Carey

But the weirdest behaviors may befall bees. Before 1932’s total solar eclipse, ecologists put out ads in New England newspapers, asking citizens to mail in any strange accounts of animal behavior. At night, bees typically switch off and rest in their hives. But during this eclipse, beekeepers up and down New England noticed signs of “apprehensiveness” in honeybees just before darkness fell.

“As darkness increased, the outgoing bees diminished in numbers and the return battalions grew larger,” one observer reported.

Daytime birds tend to roost during eclipses, but keep an ear out for a cock-a-doodle-doo and a hoot-hoot. Both roosters and owls get tricked by the blackness of the eclipse. Those on the coast may notice seabirds takeoff. A naturalist in Venezuela in 1998 witnessed frigate birds and pelicans disappear just before the eclipse and return just after. He also observed gulls flying rapidly back and forth in tight packs during the totality.

Watch out for weird squirrels too. During a partial solar eclipse in 1969, squirrels in Southern California began zipping back and forth. The rodents spent three times as much time running and were twice as active as normal.

4. Earth’s total eclipse is unlike any other

Earth is the only place in our solar system where a total solar eclipse is possible. Other planets, like Jupiter, have eclipses. Mars can have two in a single day. But their moons aren’t placed to perfectly mask the sun.

By pure coincidence, the sun happens to be 400 times larger than Earth’s moon, but also 400 times farther from our planet. That makes the sun and moon appear exactly same size in the sky. And if not for the moon’s misaligned orbit, we would see solar eclipses once a month, akin to the frequency of a full moon.

5. Enjoy solar eclipses while they last

The same physical forces behind ocean tides — tidal friction — is also causing the moon’s orbit to gradually become larger and larger. So 600 million years from now, the moon will be too far away to fully block out the sun. All the more reason to enjoy this one while it’s still stellar.

Editor’s note: The Gordon and Betty Moore Foundation is a funder of the PBS NewsHour.

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