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Explore different types of solar eclipses by using your thumb to “eclipse” a partner’s face.
Working with a partner, choose who will be “the Sun” and who will be “the Earth.” The Sun person’s head will represent the Sun in the sky; the Earth person’s thumb will represent the moon.
Start by facing each other from 9 to 12 feet (3 to 4 m) away. (Click to enlarge photo below.)
Have the Earth person close one eye and extend a thumb (the moon) toward the Sun (their partner’s face). Where does the “moon” need to be in order to just barely block the face of the “Sun”? Partners may need to move closer together or farther apart so the thumb of the Earth person can “eclipse” the face (ears included) of the Sun person. When the moon just barely covers the Sun’s entire face, a total solar eclipse occurs. (Click to enlarge animated gif below.)
What happens when the moon is slightly farther away from Earth? Make a prediction, and then test it! Have the Earth person move to a place where the Sun person’s face is covered, but their ears and the top of their head are just visible. This is a model of an annular solar eclipse.
What happens if the moon is too high? If it’s too low? Experiment and notice that there’s only one position in which the moon completely blocks the face of the Sun. When the moon blocks part, rather than all, of the Sun’s face, the result is a partial solar eclipse.
Have partners switch places and try these explorations again, so both have an opportunity to see these events happen.
In this Science Snack, you can experiment with models of total solar eclipses, annular solar eclipses, and partial solar eclipses, and see how they occur.
Though the Sun is much, much larger than the moon, and much farther away, from our point of view on Earth we see a total solar eclipse when the moon perfectly covers the faraway Sun. A total solar eclipse (click to enlarge photo below) can only occur when the moon—at its new-moon phase—comes between the earth and the Sun.
The moon’s orbit is actually tilted 5 degrees with respect to the ecliptic, the apparent path of the Sun across the sky. (It’s called “the ecliptic” because this is where eclipses can happen when crossed by the moon.) The moon’s orbital tilt is why we don’t have solar eclipses during every new moon: The new moon is usually too high or too low to block out the Sun.
In an annular eclipse, the moon is too far from Earth to entirely block the Sun. In this situation, the moon blocks out all but the Sun’s outer ring (click to enlarge photo below).
A partial eclipse occurs when the moon is not exactly aligned with the Sun, so it covers only a part of the Sun’s face (click to enlarge photo below).
This Science Snack is a short, simple introduction to the concept of solar eclipses. It’s accessible for younger learners and requires no special materials.
When you’re done with this investigation, ask students to draw a model of the Sun, the earth’s orbit around the Sun, and the moon’s orbit around the earth. Ask them to predict where the moon would need to be in order to cast a shadow across the surface of the earth. This type of modeling helps learners build a conceptual understanding of eclipses.
The material contained in this document is based upon work supported by a National Aeronautics and Space Administration (NASA) grant or cooperative agreement. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of NASA.
Create a scale model of the earth-moon system using different-sized spheres.
Discover the “cosmic coincidence” that makes solar eclipses possible!
Make a scale model of a total solar eclipse!
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Attribution: Exploratorium Teacher Institute