Lunar Homer

For many people on Earth — baseball is a favorite pastime. But how different would it be if home plate were on the moon?  A reader from Texas asked, “If baseball were played on the moon, how far would the home run fences have to be from home plate?”

Well, the moon’s gravity pulls with only about one-sixth the pull of earthly gravity. So a batter on the moon could send a baseball six times farther than the same baseball hit on Earth. If this were the only effect, the center field fence in a typical baseball stadium would have to be about six times farther away.

But the moon doesn’t have an appreciable atmosphere — so there’s little or no air resistance on the moon. A baseball hit in our atmosphere travels only 60% as far as one hit in a vacuum. Since the moon’s atmosphere approximates a vacuum, you can increase the range of the ball hit on the moon again — this time by a factor of about 2.

So a typical center field fence on the moon would need to be about 12 times farther than on Earth. What’s more, the tension might mount in lunar baseball when it came time to throw a pitch. Without air resistance, a fast ball would be really fast! On the other hand, a space suit might hinder a good wind up — and curve balls, which rely on air resistance, wouldn’t be possible.

If you want to learn more about the mechanics of baseball this is an excellent book: Adair, Robert Kemp. The Physics of Baseball. (HarperCollins: New York, 1995).

What you have in your mind?