Earth, Sun, Moon: three objects in space whose interactions have quite a gigantic impact on our lives. The Earth orbits the Sun once a year and rotates on its axis approximately once a day (depending on your definition of “rotation”). This gives us a day and night sequence and an annual cycle of seasons.
The moon’s gravitational force affects tides. We can also see the phases of the moon in the monthly cycle, which are caused by the relative position of these three spheres. The full moon enables night vision. Before electricity, this was a gigantic deal.
You can see how these interactions shape our entire concept 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 imagine you can’t. Distances and size differences make this virtually impossible.
Let’s say we want to build a model of just the Sun and Earth. The Earth has a radius of about 6,371 kilometers (3,959 miles), but let’s represent this using a marble 1 centimeter in diameter. To keep it to scale, I’d have to utilize a giant sun beach ball – the kind people throw at rock concerts – over a meter in diameter. It can hold 1.3 million balls.
But wait! It’s getting worse. This 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.
Modeling the Earth and Moon would be easier. If we utilize this ball as the Moon, the Earth will be a tennis ball with a diameter of 6.7 centimeters. Now the fun part. How far apart should we space them? Guess. You’re probably wrong because we never see the Earth and Moon together. The answer is: 2 meters. Here’s what it would look like:
Illustration: Rhett Allain