Are There More Grains of Sand on Earth or Stars in the Sky? Scientists Finally Have an Answer

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What child (or adult, really) hasn't wondered if you can count the grains of sand on Earth?. Peerayot/Shutterstock

It's a question that every future scientist probably asked during that first trip to the beach as a child: Are there more sands of grain on Earth, or stars in the sky? Well, scientists now finally have an answer, and it might surprise you, according to NPR.

Though it would be an impossible task to actually count the sand and stars, a group of scientists at the University of Hawaii recently came up with a reasonable way to get an estimate. And since Hawaii is home to some of the world's most renowned observatories and beaches, we'll take their word for it.

They began with postulating an average size for a grain of sand and by calculating the number of sand grains in a teaspoon. Then the number of beaches and deserts in the world were factored in. Multiplied all together, the number is staggering. Since you aren't likely to own a calculator with enough digits to represent the result, here it is in shorthand: 7.5 x 1018 grains of sand. In simpler, though equally as incomprehensible terms, that is 7 quintillion, 500 quadrillion grains. Or in terms simpler still: a lot.

Calculating the number of stars is even trickier, since the limits of space are still largely speculative. Our scope is limited to what we can view from Earth and Earth's orbit, with our eyes and telescopes. If we opt to limit our scope to the number of stars that are observable with the naked eye, on a clear night from Earth, then the grains of sand will get an easy victory. Even with minimal light pollution, we aren't likely to make out more than a few thousand stars. So scientists upped the ante by estimating the number of stars that are potentially observable by Hubble. If you include every object that twinkles in the night sky, from ordinary stars, to quasars, to red dwarfs, to whole galaxies, etc., then the number of stars in the observable universe is astounding. The number? 70 thousand million, million, million stars.

For the mathematically disinclined who may still wonder which number is larger: It's the stars, by far. But before we're ready to crown a champion, let's put things in perspective. Earth is one tiny little planet in the context of the whole universe. The fact that it contains so many sand grains compared to the number of stars in the sky is pretty awe-inspiring. It just goes to show that the universe is just as vast when you look at it closely as when you look at it from far away.

To put this fact in even sharper perspective, the University of Hawaii researchers decided to add a third contestant. They asked: How many molecules are there in a drop of water? It turns out that it takes just 10 drops of water for the number of H2O molecules to equal the number of stars in the sky.

That's pretty mind-blowing, when you really consider it. The thought experiment might also beckon another way of thinking about the vastness of the universe: Perhaps everything that we know to exist is itself contained entirely within a single "cosmic" raindrop, just one of countless other such drops in the whole of reality.

It just goes to show, perhaps the only thing as limitless as the universe itself is the human imagination and our sense of wonder.