Earth, sun, moon: three objects in space whose interactions have a pretty big impact on our lives. The Earth orbits the Sun once a year and rotates on its axis about once a day (depending on your definition of “rotate”). This gives us the night-day sequence and the annual cycle of the seasons.
The moon’s gravitational pull influences the tides. In a monthly cycle, we can also see the phases of the moon, which are caused by the relative positions of these three orbs. The full moon allows you to see at night. Before electric lights, this was a big problem.
You can see how these interactions structure our entire idea of time. So if you were writing a science textbook, you’d want to include an illustration of the Earth-sun-moon system, right? But guess what, you can’t. The distances and differences in size make it practically impossible.
Let’s say we want to build a model of the Sun and Earth alone. The Earth has a radius of approximately 6,371 kilometers (3,959 miles), but let’s represent it with a marble 1 centimeter in diameter. To maintain scale, I would have to use a giant beach ball as a sun (the kind people hit at rock concerts) over a meter in diameter. It could fit 1.3 million marbles.
But wait! It gets worse. That beach ball would also have to be 117 meters away. That’s longer than a football field. Now try to take a photo of the ball and the marble. Good luck with that.
Modeling the Earth and Moon would be easier. If we used that marble for the moon, the Earth would be a tennis ball, with a diameter of 6.7 centimeters. Now comes the fun part. How far apart do you think we should put them? Guess. You’re probably wrong because we never see the Earth and the Moon together. The answer is 2 meters. This is what it would look like:
Illustration: Rhett Allain