THE GREAT SAND DUNES
Input this simple equation into Wolfram Alpha:
number of stars in the observable Universe
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number of grains of sand on Earth
number of stars in the observable universe = 3 x 10 to the power of 23
number of grains of sand on Earth = approx. 1 x 10 to the power of 20
Results:
(0.2 to 4000)
Therefore, there are probably more stars in the Universe than there are grains of sand on this Earth.
NOW, INPUT THIS Query INTO WOLFRAM ALPHA:
number of atoms in a grain of sand
Results:
6.495 x 10 to the power of 20 atoms*
Therefore, there are probably almost as many atoms in a single grain of sand as there are grains of sand on this Earth.
SOURCES AND FURTHER READING:
Pieter G. van Dokkum and Charlie Conroy (2010).
*Note that sand particles can vary in size, and their composition - of silica and oxygen particles - will vary depending on location.