Astronomers say there are more stars in the universe than there are grains of sand on all the beaches on earth. How do they know how many grains of sand there are in the whole world?
In: Mathematics
We can estimate both the volume and mass of the Earth. Take a bucket of sand, weigh it, measure its volume, then count the number of grains of sand in it. You now have an estimate of the number of grains per kg or per litre of sand. You can use that to estimate the maximum number of grains. We could assume the whole world were nothing but sand, take the mass of the Earth and multiple it by the number of grains of sand in a kilogram, and you’d have the maximum possible number of grains. Obviously the whole Earth isn’t made of sand, so we could be a little more careful.
We could assume the top km of the Earths crust was made of sand, and multiple that volume by the number of grains of sand in a litre. This would be closer.
Keep repeating this process and you’d get a ballpark figure of the number of grains of sand on Earth. Not an exact number, but a reasonable maximum.
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