Beaches. And Deserts and Sandboxes.

Perhaps you’ve heard this before: There are more stars in the universe than all the grains of sand in all the beaches, desserts and sandboxes on Earth.

There are a lot of sand grains on Earth. Sand constitutes a major fraction of the makeup of Earth. Scientists estimate the number by measuring the average size of a sand grains, then calculating how many sand grains it would take to fill, say, a gallon jug. Using the latest geological studies, they calculate the total volume of sand on Earth. Scientists estimate that Earth contains 7.5 sextillion sand grains. That is 75 followed by 17 zeros. That’s a lot of sand.

Astronomers calculate the total number of stars in the universe by studying nearby galaxies, ones in which we can count the stars, to see how many it takes to make a galaxy shine. Then, based on detailed counts of galaxies we can see, and making conservative estimates of how many we can’t see, they estimate the total number of stars in the universe. Our universe contains at least 70 septillion stars, 7 followed by 23 zeros.

Astronomers estimate there exist roughly 10,000 stars for each grain of sand on Earth. That’s a lot of stars.

Credit NASA-ESA

Astronomers recently discovered the origin of sand grains. For years, they believed that only sun-like stars created lots of carbon and silicon dust, and the silicon dust is the source of sand. That meant that the universe had to evolve to the point where there were lots of sun-like stars before lots of sand could accumulate. Recently, astronomers discovered the galaxies that formed very early in the universe, before many sun-like stars could form, contained a lot of dust. Long before stars like our sun were common, planets like Earth may have formed.

There may be a huge number of planets in our universe capable of supporting life.

On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission form the Oklahoman and www.newsok.com.