The Mental Floss Field Guide to Viewing the Solar Eclipse

A total solar eclipse will cross the United States on August 21, 2017, and if you want to catch it, you'll probably want to start making preparations now. To see the total eclipse (which you really want to do!), you will need to travel to the path of totality. Mental Floss spoke to Mitzi Adams, a heliophysicist at NASA Marshall Space Flight Center, about everything you need to know to see the Sun disappear, photograph the process, why it's important to scientists, and how cultures around the world have interpreted the celestial phenomenon.

WHAT AM I LOOKING FOR DURING THE ECLIPSE?

The total solar eclipse is made up of phases. First, there's first contact, when the Sun and Moon first "touch." This leads into the partial phase, when it looks like someone is taking increasingly large bites from the Sun. Next is the actual eclipse itself, when the Sun is totally covered by the Moon. It lasts a very brief time, from a few seconds to just over two minutes, depending on where along the path you view it. The Sun passes through partial phases again as the Moon continues on its way. During the total phase, remove your eclipse eyewear and behold the corona of the Sun, wispy, revenant limbs of light reaching from a black hole in the sky. Stars and planets will be visible as day has turned to an eerie, ethereal night.

Down on the Earth's surface, says Adams, you'll notice that nature has no idea what's going on. "During the total phase when the light from the Sun's photosphere is completely blocked, some animals react," she tells Mental Floss. "The cows may start walking toward the barn. Horses may do the same. Crickets start chirping. You'll hear frogs. Birds will go to roost. Chickens will react the same way they do at sunset. All animals, including the human ones, react to eclipses in some way. The human reaction is typically, 'Wow! Look at that!'"

WHAT TOOLS CAN I USE TO VIEW AN ECLIPSE (WITHOUT GOING BLIND)?

During the partial phase of a total eclipse, you need to wear special eclipse glasses that protect your eyes from the Sun. This isn't some overly cautious government recommendation that only the squares follow. If you don't wear the glasses, you won't be able to see anything that's happening because you are staring at the Sun. Eclipse glasses can be found online, at public libraries and museums, and, along the path of totality, science advocacy and public education initiatives should have glasses freely available in large quantities. By the time the eclipse gets here, if you can't find glasses, it's because you didn't want to find them.

If you want to up your game, though, the Bill Nye Solar Eclipse Glasses might soon be the It-item of Milan's runways. Described as featuring a "stylish frame that is fashionable for both men and women" (complete with a silhouette of Nye's face on one of the arms), these glasses are "built to last"—and they would have to be. It will be seven years before the next total solar eclipse over North America.

Eclipse glasses will not magnify the eclipse. You can, however, use a telescope or pair of binoculars if you want to get a closer look. You really need to know what you're doing, though, and if this is your first eclipse, ask yourself if it is worth fiddling with knobs during what might be a once-in-a-lifetime event. If you're going to use a telescope, though, here's some advice from the heliophysicist:

"The safest way is to have a special filter that will fit over the front of the telescope," says Adams. "The telescope could be a refractor or a reflector. Binoculars would also work, though you want either two filters, or one filter while you block the light over one side of the binocular pair. Any of these filters will fit over the front."

The filters will be made of mylar or glass, she says, and warns that they must be specifically certified as safe for viewing the Sun. "You do not want to use any kind of filter that will screw into an eyepiece because they will crack, and it doesn't take very long—just a couple of seconds—to build up the heat to crack the filter."

If you want to view the Sun up close during the partial phase of the eclipse, be on the lookout for sunspots, the darker areas seen on the surface of the Sun. The current phase of the Sunspot cycles suggests that there won't be any Sunspots large enough to see with the naked eye. With a telescope, though, you might have better luck.

WHEN NASA LOOKS AT THE SUN, WHAT ARE THEY LOOKING FOR?

"We want to learn as much about Sun as possible," says Adams. "We're trying to study from the core of Sun all the way out to the corona, which is the outer layer of the Sun's atmosphere. The eclipse will enable us to study the inner corona. We can actually build pictures of events on Sun from the photosphere, through the chromosphere, and into the corona."

Scientists will combine the visible light images that they get from the eclipse with images from sources such as NASA's Solar Dynamics Observatory in orbit around the Earth. The observatory views the Sun in multiple wavelengths—mostly extreme ultraviolet—continuously, but it is unable to get the inner corona in visible light. "We can't really study the full spectrum unless we're using images from a solar eclipse," says Adams.

HOW DO I PHOTOGRAPH THE ECLIPSE?

Nikon has provided a comprehensive guide to photographing the Sun both conventionally, on a tripod, and with a special telescope mount. Eclipse2017 also has a useful set of pointers for how to preserve the moment. But the big thing to remember is, DO NOT USE A FLASH—not for reasons related to photography (though seriously, do you think your Galaxy S6 flash is strong enough illuminate the entire sky?) but because part of the wonder of the event is the day turning to night! Light pollution is already a problem for skywatching. Don't turn the eclipse into a light toxic waste dump. (Do not use a flashlight, either.) The best photography advice might be to keep your camera at home and enjoy the total eclipse with your eyes—not through a glass screen.

CAN I HELP DO SCIENCE?

Yes, and the American Astronomical Society has you covered. There's Citizen CATE, in which amateur astronomers across the country will use identical cameras and telescope equipment to take pictures of the Sun's inner corona; the Do-It-Yourself Relativity Test, in which, during the eclipse, you can "measure the gravitational deflection of starlight and prove for yourself that Einstein really was right" with no special equipment; the Eclipse Megamovie Project, which will use images and footage taken of the eclipse by citizen scientists across the country, and, from that, stitch together a high-definition video of the eclipse; and there are many, many others.

WILL TRAVEL BE A PROBLEM?

Yep! Finding a hotel room will be a problem. Entrepreneurial members of Airbnb who live along the path of totality are renting out square footage in their yards for people to set up tents, and they're charging hundreds of dollars for the favor. Your best bet for finding a reasonably priced room is Nashville, which is the largest city on the path and a major tourist destination year-round. Traffic will be a problem, though nobody knows how bad, exactly, because it's been 38 years since an eclipse path of totality passed over the continental United States, and nearly 100 since the last coast-to-coast eclipse. What you need to know is that 200 million people live within a day's drive (about 500 miles) of the path. It doesn't take a civil engineer to imagine how that might go. Parking will be a problem. Make sure your gas tank is full, you have food and water in the car, and for the love of all that is good and holy, insist that the kids try to use the bathroom before you get on the highway. It might be a very long, very slow drive even for short distances.

I HAVE KIDS—WHAT DO I DO WITH THEM?

Bring them! Most of the communities along the path of totality are pulling out all the stops. While you wait for the (very brief) show, there will be plenty of entertainment, and NASA will have beachhead presence across the country with science demonstrations for kids and adults alike. Just make sure everyone has their own pair of eclipse glasses.

THE ECLIPSE WILL NOT CHANGE THE SUN'S RAYS AND GIVE YOU CANCER.

There are a lot of mistaken beliefs about eclipses that should be put to rest. "One large misconception is that somehow going outside during the eclipse is dangerous—that there are somehow 'eclipse rays' that happen, and that the Sun is more dangerous during an eclipse," says Adams. "That's just not true. The light from the Sun is exactly the same from an eclipse as when it's not eclipsed."

Likewise, staring at an eclipse when it is at totality will not make you go blind. Indeed, during totality, that's when you take off your eclipse glasses and specifically stare at the Moon-concealed Sun.

WHAT GROUPS ARE CELEBRATING THE EVENT?

The entire U.S. will see at least 70 percent coverage of the Sun, which is pretty good when compared with the 0 percent coverage we get every day. As such, the whole country will evolve into one massive solar celebration, with literally thousands of parties and viewing events being held at schools, libraries, museums, parks, amateur astronomy groups, university astronomy departments—you name it, they're doing it. There are multi-day music festivals in Oregon and Illinois, the latter of which is called Moonstock, with Ozzy Osbourne headlining.

Even if you live outside the path of totality, NASA will help you host an eclipse party. They've even built an international map of experts that you can reach out to for party entertainment. (Ozzy Osbourne will not have useful astronomy advice, I can assure you. But Brian May, on the other hand … )

WHERE WILL HAVE THE BEST WEATHER FOR THE ECLIPSE?

The entire path of totality has a reasonable chance of good weather. For the very best weather in the country on eclipse day, Great American Eclipse says that Oregon is the place to be. "While the Oregon coast is at risk of marine clouds," they report, "the interior of this state actually enjoys the nation's best weather prospects." Snake River Valley, Idaho, and western Nebraska are also recommended for their extensive network of highways and farm roads. If clouds roll in, you can easily relocate to some place more favorable.

HOW HAVE CULTURES INTERPRETED ECLIPSES OVER THE CENTURIES?

Our friends at the Lunar and Planetary Institute have commissioned an extraordinary collection of multicultural eclipse folktales, performed by professional storytellers Cassandra Wye and Fran Stallings. The stories reveal how people around the world going back centuries have explained and interpreted eclipses, from the Batammaliba people of Africa, whose eclipse origin story sees the Moon taking revenge on the Sun, to the Anishabe people of North America, for whom the Sun was briefly imprisoned.

Does Sound Travel Faster or Slower in Space?

iStock/BlackJack3D
iStock/BlackJack3D

Viktor T. Toth:

It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.

But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.

For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.

However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.

So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.

How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).

This post originally appeared on Quora. Click here to view.

The Orionid Meteor Shower Peaks This Weekend

iStock/Kazushi_Inagaki
iStock/Kazushi_Inagaki

October is always a great month for skywatching. If you missed the Draconids, the first meteor shower of the month, don't despair: the Orionids peak this weekend. If you've ever wanted to get into skywatching, this is your chance.

The Orionids is the second of two meteor showers caused by the debris field left by the comet Halley. (The other is the Eta Aquarids, which appear in May.) The showers are named for the constellation Orion, from which they seem to originate.

The shower is expected to peak overnight from Sunday, October 21, to Monday, October 22, when you can plan to see 15 to 20 super-fast meteors per hour. The best time for viewing is between 2 a.m. and 5 a.m., when Orion appears completely above the horizon. Make a late-night picnic of the occasion, because it takes about an hour for your eyes to adjust to the darkness. Bring a blanket and a bottle of wine, lay out and take in the open skies, and let nature do the rest.

There's a chance that the Moon might interfere with the meteors' visibility, according to Space.com. Leading up to its full state on October 24, the Moon will be in a waxing gibbous phase, becoming larger and brighter in the sky as the Orionids speed past Earth. Limiting light pollution where you can—such as by avoiding city lights—will help.

If clouds interfere with your Orionids experience, don't fret. There will be another meteor shower, the Leonids, in November, and the greatest of them all in December: the Geminids.

A version of this story appeared in 2017.

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