Grains Of Sand vs Stars In The Sky

Sep 26 2012 @ 8:28pm

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Robert Krulwich solves the eternal quandry with help from David Blatner's forthcoming book, Spectrums: Our Mind-Boggling Universe, from Infinitesmal to Infinity:

They said, if you assume a grain of sand has an average size and you calculate how many grains are in a teaspoon and then multiply by all the beaches and deserts in the world, the Earth has roughly (and we're speaking very roughly here) 7.5 x 1018 grains of sand, or seven quintillion, five hundred quadrillion grains. That's a lot of grains. 

But if you got a Hubble telescope and counted all the "distant galaxies, faint stars, red dwarfs, everything we've ever recorded in the sky" you'd end up with  "70 thousand million, million, million stars in the observable universe (a 2003 estimate), so that we've got multiple stars for every grain of sand — which means, sorry, grains, you are nowhere near as numerous as the stars."

(Photo: Blue Straggler Stars in Globular Cluster M53 by ESA/Hubble via NASA)