Carl Sagan famously said that:

The total number of stars in the Universe is larger than all the grains of sand of all the beaches of the planet Earth

Sitting on the beach last week, I wondered if this could possibly be true. While looking at the number of grains in my hand, imagining the number on just one beach seemed inconceivably large. Obviously we cannot know for sure, but some quick calculations indicate that it is in fact true. According to this post there are 10^20 grains of sand on earth and 10^22 stars in the known universe. That gives at least 100 stars for every grain of sand on Earth. That is a big universe, and that’s just the part we know about.

At the other end of the spectrum of inconceivable numbers, it’s also true that there are more atoms in a glass of water than stars in the universe (there are 10^25 atoms in a glass of water). As the universe is incredibly large; atoms are incredibly small.

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