13: Solar and Lunar Eclipses

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Caution

NEVER look directly at the Sun! Not with sunglasses, not through a camera, definitely not with a telescope or a binocular, not even through a welder’s mask. NEVER LOOK AT THE SUN DIRECTLY!

Solar and lunar eclipses are the stuff of legends. The spectacle of the Moon going dark and then becoming blood-red for hours at a time, or the horror of the Sun being devoured until the world stood in darkness at midday was enough to chill the blood of any ancient or primitive soul that witnessed them. Columbus himself is supposed to have used a solar eclipse prediction to convince the Native Americans that he had great mystical powers and should be left to his business; Mark Twain incorporated this story in his book A Connecticut Yankee in King Arthur’s Court.

But why do eclipses happen? Some students may know that the eclipses have something to do with the shadows of the Earth and Moon, but if that is true, why don’t they happen every month? In this unit, we will not only investigate the phenomena of lunar and solar eclipses, we will see once again that we can take an existing model of the solar system, and add new features to it that will not only increase its richness, but also improve its usefulness and allow us to make even more testable predictions!

13.1: Modeling a Solar Eclipse
This activity will take our Earth-Moon system model to new levels of detail. In order to do this, we are going to have to make a new model on a different scale. Like so many scientific models in astronomy, this one will fib a little bit when it comes to the real scale of the solar system. As we’ve seen in Activity #3 (Making a Scale Model of the Earth-Moon System), the distance to the Moon is very large, and that would make our model rather impractical for us.
13.2: Modeling a Lunar Eclipse
At first glance, our lunar eclipse activity will look much like the solar eclipse (Activity #34), but there are subtle differences worth noting. We will use the same rubber T-ball model Earth and foam core lunar orbit ring that we used last time, but this time we will be using a paper cone to represent the Earth’s shadow instead of the Moon’s shadow.
13.3: Why are Eclipses so Rare?
Total solar eclipse events last only minutes, and one has to be in a very exact position to observe them. Adventurers, astronomers, and wealthy tourists take trips to exotic locations, people even charter cruise ships to travel to a particular point in the ocean and drift motionless while those on board observe the fleeting event! The model we created seems to suggest that an eclipse should be possible every full and new moon – so why are they so infrequent?

Thumbnail: Totality during the 1999 solar eclipse. Solar prominences can be seen along the limb (in red) as well as extensive coronal filaments. https://en.Wikipedia.org/wiki/Eclips..._1999_4_NR.jpg