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How many grains of sand are there in the Sahara desert?

and don't say a lot

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I just counted it was 12345473663 grains..... Wait no 1234573689 grains.... Dammit!

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ha ha
really funny
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Woah! Nobody knows! You could be the first person to find out; go count them! :D

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no thanks
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What else is there?

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The key point is that you don't need to count: you can easily get an order of magnitude estimate, and be wrong by a factor of perhaps a few if you treat it as a Fermi problem. So here is how I estimate it:

The area of the Sahara desert (from Wikipedia) is 9.4x10^6 sq. km, or 10^7 sq. km = 10^13 m^2.

The average depth of sand: couldn't readily find it, so I estimate as 5 m. That's because there are very deep dunes, but also rocky areas, so 5m sounds not unreasonable.

The volume of sand is therefore 5x10^13 m^3.

The volume of a grain of sand is tricky: they come in many different sizes, spanning 6 orders of magnitude. A large grain of sand is 10^(-9) m^3, and a small one is 10^(-12) m^3. Let's assume the average sand grain in the Sahara is a medium one, whose volume is 10^(-12) m^3.

Dividing the two volumes, the number of grains of sand in the Sahara is 5x10^13/10^(-12) ~ 5x10^(25). The factor of 5 can of course be dropped.

So the answer is 10^(25), or 1 with 25 zeros after it.

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Yeah, but what if it was windy that day? : )
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doesn't matter. The order of magnitude remains the same. The wind will maybe change a fraction of one percent.
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Kewl! : )
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thanks
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I had one typo: the size of a small gain is 10^(-15) m^2. It doesn't change the estimate.
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Dee s and does

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what?
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all of them and dees
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A lot.

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Hey Deb! How's it going with those younguns??
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Not good, kbevans, not good. And the one I gave is an adult.
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*have
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hey!!!!! did i say to not say a lot?
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dees
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