On Monday, August 21, 2017, North America will experience a solar eclipse. An eclipse of this size has not been experienced in North America since 1979. The next one won’t be until Monday April 8, 2024.
The path of totality – where the moon will block all of the sun will stretch from Lincoln Beach, Oregon to Charleston, South Carolina. Locations that are outside this path will experience a partial solar eclipse.
According to NASA the thin path of totality will pass through portions of 14 states.
Regardless of where you are, an eclipse is a teachable moment. It is dangerous to your eyesight so you must not look directly at the sun during an eclipse without the use of special viewing glasses that you can purchase. If you do not have glasses, there is another option to use a pinhole projector to help you see an image of the sun safely. Originally invented by Leonardo da Vinci and called a “Camera Obscura”; pinhole cameras can be made so that you can watch the eclipse safely projected inside the camera.
Luckily, NASA has already designed the cameras and they can be downloaded. They have downloadable files for every state as well as the entire continental US and the District of Columbia. Head to the NASA site for more information as well as the files.
“During the 2016 total solar eclipse in Micronesia, NASA tested a variety of pinhole sizes using 3D printed cards and found that a 5 mm pinhole held 3-4 feet above the ground provided the strongest and clearest pinhole projection of a partial eclipse” ("3D Printable Pinhole Projectors | Total Solar Eclipse 2017", 2017).
As an extension to this you can create models of the sun, earth and moon to use to create a simulation for students.
Why can two objects that are very different in size appear to cancel each other out in an eclipse? Well, one of the interesting facts about the earth, moon and sun has to do with the number 400. The sun is about 400 times bigger than the moon, but the moon is about 400 times closer. The result is that they appear to be the same size and one completely obscures the other as seen from Earth. To create a model, one of the nice things about 3D printing software is that you can easily create three spheres and you can create them to scale for your students. You can create your own, and set them up with the appropriate ratios, or you can head to stlfinder and find some models already created to download and print.
Once you have the printed models, you can encourage students to experiment with a flashlight to discover the distance/mass ratio for a total eclipse to occur.