Are there more stars in the universe than grains of sand in the Earth?

  • My ten year old daughter asked me this question at breakfast and I initially said yes, but on second thought I was also puzzled.


    From @AndrewGrimm 's link, 10^20 to 10^24 grains of sand, 7x10^22 stars. You can shrug and tell her "dunno" ;)

    @JollyJoker about a mole of each.

    According to Neil deGrasse Tyson, there are indeed. And if it's good enough for Neil deGrasse Tyson, it's good enough for me.

    The estimates of each quantity are so plentiful as to vie with the answers themselves in magnitude.

  • A quick google gave me these (approximate) figures:




    • 7.5 x 1018 grains of sand in all the beaches and deserts of the world


    • 7 x 1022 stars in the observable universe




    If these are reasonable estimates, then there are approximately nine thousand stars in the observable universe for each grain of sand on Earth. (By observable universe, I mean in all the galaxies that we can detect with our most powerful telescopes.)



    Robert Krulwich: Which Is Greater, The Number Of Sand Grains On Earth Or Stars In The Sky?


    How much sand is there in all the other places? ;-)

    Nitpick: the observable universe has nothing to do with telescopes. Merely whether EMR emitted from the source after the recombination epoch has had sufficient time to reach Earth. Whether or not we can detect it is irrelevant (ironically enough.)

    @corsiKa Good point. I was a little unsure myself about that.

    The number you've quoted is all the grains of sand ***on beaches***. Presumably the number of grains of sand in all the world (including under the sea) would be *dramatically* larger given that beaches and deserts represent less than a tiny fraction of the area of the ocean.

    @Valorum Beaches and *deserts*. And doing some Googling, it seems the ocean floor is mostly rocky, not sandy. Only coastlines are sandy, and they were hopefull included in the calculation.

    Since the calculations only use *visible* beaches, I'd imagine that the number is out by at least 100% even if you only account for the sand a few miles offshore.

    @Valorum does the "tiny fraction" mean 0,01% ? because anything bigger than this means the stars still win.

    @Mindwin - I don't know what methodology they've used to represent the area of all the beaches in the world. I do know that more than 71% of the entire globe is covered in water. Assuming that they've represented the beaches and deserts as 5% of the Earth's surface and assuming each cubic meter of water has 0.01% as much sand as a cubic meter of beach, it could easily be *hundreds of thousands of percents* out. I am, however no expert on sand suspension in sea water

    Even if you double the number of grains of sand because of a 100% error it will still be much less than the 4 orders of magnitude more observable stars.

    Fortunately, if you want to give them all an ID number, there are enough GUIDs for all the stars, all the grains, and plenty spare :)

    The area where I live (around Berlin, Germany) is mostly sand under a small soil cover. It doesn't look like a desert at all. I guess this was not included in the count?

    The statement in question has an implicit "common-man" assumption of only counting beaches and deserts. In a TV program, the presenter will hold up a handful of sand on a beach, not dig a hole in Berlin or dive to the bottom of a river or the ocean, for example. Plus there's a desire to not run into niggling issues of what the technical definition of "sand" is.

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Content dated before 7/24/2021 11:53 AM

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