How to enjoy the eclipse, and not burn out your eyes

Early Monday afternoon, Aug. 21, the skies will darken across Minnesota as the moon passes in front of the sun. For even the most casual of skygazers, this is a big deal.

It will be the first coast-to-coast solar eclipse the U.S. has seen since 1918. Intergalactically speaking, we're lucky to be able to see eclipses. We can see them here on Earth only because of the distances that separate Earth, the moon and the sun.

In a few hundred million years, that distance will change enough that creatures on Earth won't see eclipses.

How much will we be able to see from Minnesota?

While Minnesota isn't in the path of the eclipse's totality — which is the moment when the moon fully blots out the light of the sun — for most of the state, between 70 and 90 percent of the sun will be obscured.

The prime time for viewing in Minnesota will likely last from 12:30 to 1:30 p.m. (NASA has made a PDF map showing the intensity of the eclipse at different times across the U.S. The Washington Post has a great explainer, too.)

But before you make plans to catch this rare event, know that it can be dangerous — even partially blinding, permanently — to look at an eclipse without proper eye protection.

Here's why, according to the producers of the Brains On! science podcast for kids:

"Our eyes are made to take in light, but not this much light.

The sun is really, really, really bright. It's so bright, that regular sunglasses won't do you any good if you're staring right at it. Normal sunglasses block 80-85 percent of visible light.

But there is so much visible light coming from the sun [during an eclipse] that in order to not damage the cells in your eyes, you need to block out 99.9996 percent of it."

Need another reason to play it safe? Your body can't tell if your eyes are being burnt in the sun, so you won't realize anything's wrong until well after it happens. And the length of time your retinas are exposed to the light doesn't matter much — even small amounts can damage your eyes.

How to protect your eyes

Protecting your eyes isn't hard. Many public libraries are giving out free eclipse glasses. But many are also getting bombarded with requests for the glasses, so it's best to plan on bringing your own.

The American Astronomical Society has a list of reputable places to buy the inexpensive glasses, too. But beware of inadequate glasses, some of which are being sold online. According to the Boston Globe, "the proper lenses should meet what's called 'ISO 12312-2' (sometimes written as 'ISO 12312-2:2015') international safety standards."

Make your own eye protection

You can make your own eye protection, too. Here's our guide on making a pinhole projector:

How to make a pinhole projector

What you will need:

• Two pieces of stiff white cardboard (in this case, we cut up a donut box)

• A pin

• Scissors

Cut down into two pieces — a smaller section that you'll hold during the eclipse and a larger one to act as the "screen."

Then, poke a clean hole with the pin on the smaller piece, which will focus the light. Make sure to keep it as clean as possible.

To use during the eclipse: Turn away from the sun so the light passes over your shoulder.

Hold up the cardboard with the pinhole higher up, near your head. Take the "screen" and hold it farther out and below the piece with the pinhole.

Make sure the pieces are arranged so that the sun passes through the pinhole, then onto the cardboard "screen." (In the GIF below, the flashlight mimics the sun.)

To focus the image, move the cardboard pieces closer or farther away.

If you'd prefer to make a projector out of a cereal box, NASA has a good guide.

Will Lager | MPR News

Where to watch the eclipse

The most fortunate among us will be somewhere along the path of the eclipse's totality Monday. (Sun Country Airlines is even offering a trip from the Twin Cities to Grand Island, Neb. The same-day flight is now sold out.)

But you don't need to leave home to catch this eclipse: There are viewing parties across the state, many of which are being held at libraries:

• Hennepin County libraries are hosting 11 viewing parties.
• St. Paul Public Libraries will host several events, too.
• Duluth has a library gathering, as well.

Some state parks — including Afton and Tettegouche — are also celebrating.

Ridgewater College has events at its Hutchinson and Willmar campuses, with faculty on hand to answer questions.

If you're not near these events, check with a nearby library, college or state park. And if you'd like us to add your Minnesota eclipse-viewing party to our list, contact me at cnelson@mpr.org.

What else should I know?

NASA is so ready for this

A team of NASA-funded scientists will chase the shadow of the eclipse across the country in two jets. The agency is planning several other projects, too, as part of the rare opportunity to conduct research during an eclipse.

"This will be one of the best-observed eclipses to date, and we plan to take advantage of this unique opportunity to learn as much as we can about the sun and its effects on Earth," Steve Clarke, director of NASA's heliophysics division in Washington, said in a statement.

But it's not just for NASA scientists — you can do your experiments, too.

Eclipses make some animals weird

Bees get busier during eclipses, and squirrels can become restless, too. Eclipses are even more intense for cicadas.

One study found that a population of crickets stopped calling when an eclipse's shadow lowered temperatures a few degrees — they were too cold.

The Atlantic has more about research on how eclipses can affect the animal kingdom.

Some plants get confused, too

Flowers like four-o'clocks and moonflowers open at night when the sun goes away. If the eclipse gets intense enough, they'll close prematurely.

Same thing happens for plants whose flowers close at night. Watch your garden to see if anything changes when the sun is obscured.

Trees can do some cool things

Gaps between leaves can turn into tiny pinhole filters during an eclipse, casting some neat shadows. Here's a video from a 2012 annular eclipse: