eclipse science

Typically, we host our “See it!” theme each Monday during our tour. But, there’s an important “see it” kind of event on a Monday coming up, well after the parks tour is done: the solar eclipse on August 21, 2017.

Keep reading to understand more about eclipses and how to view them, but at the very end of this post is the punchline: We’ll have some solar viewing glasses to give out to Science in the Parks participants, each Monday (“See it!” day) of our tour.

At that time, many of you will be on the tail end of your summer breaks, and perhaps even more of you will be starting your first day of school. Also, here in Utah you will be just outside of the main eclipse event. But, in spite of this, there are still important things that you (and maybe your teacher and the rest of your class!) can pay attention to.

First, some background. The August 21 event is a “total solar eclipse.” This happens when, from your place on Earth, the Moon gets in the way of the Sun. Because our view of the Moon makes it look almost exactly the same width as the Sun*, the effect is to block out the Sun and all its light for your spot on Earth. The sky goes completely dark in the middle of the day! This could take place from anywhere between a few seconds to a couple of minutes, depending on where you are.

This all relies on that perfect alignment of the Moon and Sun, so it only happens at rare times and it only happens for specific locations on Earth, known as the eclipse path. This August’s eclipse is particularly rare for us in that it has such a long path across the United States, from Oregon to South Carolina.


There are many good sources for maps and descriptions of the path, including:

You’ll notice that the total eclipse path does not include Utah. So, you have a couple of options. If you have the ability to head north, you can intercept that path. There’s lots of good information on various webpages, but you still have some planning to do. (Many of us have been planning on this for years, and reportedly campsites and hotels in the area are booked.) If you can leave early enough, you should be able to make a day trip out of the event, maybe even having multiple backup plans as you watch weather reports and cross your fingers for clear skies.**

If you can’t go somewhere in Idaho or Wyoming, though, you can still get a very good viewing of a partial eclipse from here in Utah. In Ogden, for example, you’ll be able to witness a partial eclipse that, at its peak, will cover 90% of the sun. The partial eclipse here in Ogden will last from around 10:15 AM to about 1:00 PM, so I’m hoping that there will be lots of teachers taking kids out to make observations, assuming that skies are clear. (You can get details for the eclipse timing at your exact location by using an interactive map like this one, but be aware that times for these maps are usually listed in “Universal Time,” or “UT,” which does not stand for Utah Time or any such thing. This is the time at the Prime Meridian, and our local Utah time is 6 hours behind that during the daylight savings shift.)

To see the Moon getting in the way of the Sun, you have a few options. But, before that you must be very aware: NEVER look at the Sun directly, even when there’s only a sliver of it from behind the Moon. You know that you spontaneously look away from the Sun when you accidentally point your gaze towards it, and this is for a very good reason. Do not ever try to circumvent this natural, protective reaction.

One more time: NEVER LOOK DIRECTLY at the surface of the Sun. Every other resource here will tell you exactly the same thing. I suppose it’s obvious, and it’s easy to abide by this warning, and you’d probably never even think of doing it, but we want to be perfectly clear. You will damage your eyesight by looking at the Sun.

The good news is that there are some indirect methods for viewing the Sun. First of all, there’s a way to make a pinhole projection. You’ve seen these even though you might never have realized it. Here’s a photo I took just the other day of sunlight coming through the branches and leaves of a tree:

Dappled sunlight is composed of round projections of the Sun through the gaps between a tree's leaves.
Dappled sunlight is composed of round projections of the Sun through the gaps between a tree’s leaves.

Notice how you get round circles of light? Each one of those is a projection of the Sun itself! When light goes through a narrow opening such as the small gaps between leaves, there’s a neat projection of light that exactly inverts the image of whatever the source of light may be, regardless of the shape of the hole. So, you see the image of the round Sun! You can do this deliberately and to good effect during a partial eclipse. Take a piece of card stock, cardboard, aluminum foil, or something similar and put a small hole in it, perhaps with the tip of a pencil, paper clip, or needle. Then, have the pinhole pointed toward the Sun, and on the other side have a piece of paper, a screen, or even the sidewalk. If your screen is in the shadow of your pinhole board (or in the shadow of something else, like the eave of a building or even in a box), you will be able to see the projection of the Sun. If you do this during the partial eclipse, you will see the Sun being “cut” into by the Moon, rather than seeing the completely round Sun. As the eclipse progresses, you’ll get to see this cutout change. To me, seeing one astronomical objects go in front of another is one of the most inspiring things I’ve ever witnessed.***

Here is a set of instructions with photos for one version of this pinhole projection setup, courtesy of Jet Propulsion Laboratory and NASA. (They have lots of excellent resources for in and out of school educational activities — something I appreciate about our investments in NASA and JPL.) You can also do a similar projection with binoculars for a more magnified view; but, again, NEVER look through the binoculars at the Sun. (You’ll notice that all these sites are being very loud and clear about this.)

In addition to projections, many people use solar filters to look at the Sun. These are NOT sunglasses, but a very specialized filter material that will block out all but the very brightest light, such as the Sun’s. You can buy these from many of the vendors linked to some of the sites above, or from a planetarium, or even from some more general online and local retailers. With this filter, you can look straight at the Sun and see it as a perfectly orange orb. During the eclipse, you’ll see it get covered up by the Moon, bit by bit. This technique might be the most convenient, and it’s easy to have one pair of these glasses or other filter that can be shared between a few people to check on the progress of the eclipse over the span of a couple of hours.

A view of the Sun through appropriate solar filter. (It looks bigger when you're wearing the glasses. I just held the camera back to capture all the pieces.)
A view of the Sun through appropriate solar filter. (It looks bigger when you’re wearing the glasses. I just held the camera back to capture all the pieces.)

Here’s some extra good news: During “See it!” days (Mondays), we have been handing out “rainbow glasses” for kids to take home. We’ll continue to do this, but in addition we have some custom made Weber State solar glasses for anyone who can use them. You’ll have to take care of these until August 21 to use them for the eclipse, but you can also use them right away to try them out. We’re hoping that you’ll be able to use these in your backyard or even at school — and maybe teachers will also have some of these or other pinhole projections ready — so that everyone can enjoy the eclipse, even the partial eclipse viewable from here in Utah. Regardless of where you are or how you view the August 21, 2017 eclipse, I hope you witness and appreciate the wonder of the firsthand observation of a rare and marvelous astronomical display.

* You might be wondering about this and how the alignment and sizes work out exactly. The Moon is much closer to us than the Sun, but it’s also much smaller; so, the far-away-big-thing and the near-to-us-small-thing can look like they are the same size. It’s fun to look up these values and find ways to model this!

** I know of many scientists using multiple strategies, but most are going to be driving in the morning so they’re the most mobile. Some are headed to gatherings where they actually have to “work” in their astronomy roles. As for myself, I’ve planned something a little less dependable and am going to be hiking a few days into the mountains and get to a secluded pass in the backcountry — but I’ll be at the whim of nature and whatever weather pattern I get that morning.

*** I’ve seen a couple of partial eclipses like this, and I’ve seen Mercury and Venus in front of the Sun. These are right up there on my list of inspirational events, in between witnessing the birth of our children and seeing Eric Clapton play guitar.

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