Considering the Moon …

When I go glamping with my grandgirls later this summer, I want to be able to teach them about the movement of the sun, moon, and stars in the wide-open skies. But the nature of how it all works can be confusing. I recently ran across a basketball analogy that put everything in perspective. Since my son-in-law, Lucas, was a basketball coach, the girls are familiar with the game, so it will be a great way for them to remember how the moon orbits around the Earth.

First, picture a basketball court. We’ll scale the Earth down to the size of a basketball and place it in the basket. That will make the moon the size of a tennis ball. The moon, then, basically orbits the Earth at the 3-point line (that’s the line that looks like a circle about 23’ from the basket where you can’t believe Steph Curry just made a basket from).


Note: Because the moon’s orbit is really elliptic and not exactly circular, it extends away from the 3-point line at its apogee (furthest point from the Earth) and perigee (nearest point to the Earth) at about the length of a tennis racket. But I might save this little tidbit for later. No need to confuse the issue (or Nanny Jane!).

Fun fact: At this same scale (basketball/tennis ball), the sun is about the size of a very large hot-air balloon and it’s about 1 3/4 miles away from the basket. The sun and moon appear to be the same size when we look at them in the sky. However, the sun is 400 times larger than the moon. So why does it appear the same size as the moon? Because it’s nearly 400 times further from the Earth!

  1. Winnie Nielsen says:

    This is a great idea, MaryJane for helping StellaJane and Mia grasp the concept of the earth and moon. May I suggest you also throw in the idea of gravitational pull needed to keep the moon from whirling away in space. Maybe use a large rubber band to hold the tennis ball (now the earth) and a large marble(now the moon) and show the tension and pull that exists to hold the two in their movement as they continue to circle the sun. The gravity discussion allows you to talk about ocean tides as well if they have been to the beach and seen the difference between high and low tides. Of course gravity concept can start with the simple apple always falling from the tree to the earth instead of flying off into the air.

  2. Karlyne says:

    And, to follow that tutorial, my two cents worth: what a gorgeous moon it was last weekend! We got to watch it rise over the mountains to our east, through the breeze-blown clouds. It looked a lot like the above picture, only bigger and closer, and, actually, nothing like it at all…

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