Earth, Sun, Moon: three objects in space whose interactions have quite a significant impact on our lives. The Earth orbits the Sun once a year and rotates on its axis once a day (depending on your definition of “rotate”). This allows us to know the order of day and night and the annual cycle of seasons.
The moon’s gravitational pull affects tides. In the monthly cycle, we can also see the phases of the moon that occur due to the relative positions of these three spheres. When there is a full moon, you can see it even at night. Before electric lights, this was a big deal.
You can see how these interactions structure our entire concept of time. So if you’re writing a science textbook, you might want to include a picture of the Earth-Sun-Moon system. Right? But I don’t think that’s possible. This is virtually impossible due to distance and size differences.
Let’s say you want to create a model that only has the Sun and Earth. The radius of the Earth is approximately 6,371 km (3,959 miles), but let’s represent this as a marble with a diameter of 1 cm. To keep things in scale, we had to use giant beach balls for the sun, over a meter in diameter (the kind people bang on at rock concerts). It can hold 1.3 million marbles.
But wait! The situation gets even worse. That beach ball must also be 117 meters away. It’s longer than a soccer field. Now take a picture of the ball and the marble. good luck.
It would be easier to model the Earth and Moon. If that marble were used for the Moon, the Earth would become a tennis ball with a diameter of 6.7 cm. Now comes the fun part. How far do you think we should keep them? Take a guess. That’s probably wrong because we don’t see the Earth and the Moon together. The answer is 2 meters. Here’s what it looks like:
Illustration: Rhett Alain
