Do Stars Outnumber the Sands of Earth’s Beaches?
Figuring out whether there are more stars in the universe than sand grains on Earth’s seashores requires math—and imagination
One of astronomy’s lovelier aphorisms, popularized by astronomer Carl Sagan, is that there are more stars in the universe than grains of sand on all the beaches on Earth.
That’s hard to grasp, which is the point. When you stand on a beach, you can see a lot of sand. Extrapolating that to the entire planet multiplies that sum immensely. Yet according to the adage, the number of stars in the cosmos is even larger—truly an unfathomable amount.
I’ve heard this dictum many times over the years, expressed in many ways. But like many such brain-freeze-inducing sayings, it’s worth asking a very basic question: Is it true?
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