Wednesday, August 16, 2017

Wednesday Explorers Club ~ Solar Eclipse Science!

photo from NASA - eclipse seen in space

The Solar Eclipse is coming - Monday, August 21 - and if you live anywhere in North America you'll see at least a partial eclipse. A solar eclipse is when the moon passes between the earth and the sun, blocking out part (or in a swath of lucky locations, all) of the sun's light.

We all know - or at least we should know - that looking directly at the sun can damage our eyes. This holds true for solar eclipses, too. So even though the moon will block the sun's light, you can't watch the eclipse by looking at the sun -

 UNLESS you have special eclipse-viewing glasses.

Eclipse viewing glasses have special filters that protect your eyes. Regular sunglasses are NOT adequate. If you don't have a pair of special eclipse viewing glasses, check your local library. Many libraries are providing glasses and holding fun eclipse viewing parties. Find out more about eclipse safety here.

Those of us who grew up in the last century (context: it was only 18 years ago) learned a cool - and cheap - trick for viewing solar eclipses: make a projector. Instead of looking at the sun, you project the sun's image on a sheet of paper (or a white wall) and watch the moon move across the sun's image. The easiest projector to make is a pinhole projector.

How to make a pinhole projector: Find a piece of cardboard in your recycling bin (clean pizza box, cereal box, large postcard, old spiral notebook cover, even a couple paper plates). Then use a thumbtack, nail, or even sharp point of a pencil to poke a small hole through it. With your back to the sun, hold the cardboard over your shoulder and project the image onto a piece of paper on the ground or a white sidewalk.

Eclipse Science: 

What is the best size or shape of hole for a projector? The suggested size for a pinhole is 1mm, with a perfectly round hole. Will larger holes project just as well? Punch or cut a series of holes of different sizes so you can compare them during the eclipse. Which ones provide clear images? Which provide fuzzy images?

Does hole shape matter? What if you cut a triangle or square?

Does distance of your projector from the ground matter? Compare images when you hold projector close to ground, knee distance, waist distance, shoulder distance... attached to the handle of a rake and held high above the ground...

How does the world change during a solar eclipse? Before the eclipse make some notes about the temperature, how the air feels on your skin, what the surrounding environment looks like, what bird and insect sounds you hear. Continue to jot down observations as the eclipse progresses, and especially when it reaches its darkest. 

More projectors: Got a cereal box? You can turn it into an eclipse viewer with a minimal amount of materials and time. Here's how. Or try making an eclipse viewer from a tube. Instructions here. (Experiment: does tube length matter?)

Remember: it's summer, so put on your sunscreen because you can get a sunburn even during an eclipse.

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