## Thursday, December 1, 2022

### How Many Stars? How Many Molecules?

Not sure how many stars there are in the universe, I asked Dr. Google, and found a wide range of estimates, but this site seemed relatively reliable:

https://www.worldatlas.com/space/how-many-stars-are-there.html

A second source on the trillions of galaxies averaging 0.1 trillion = 100 billion stars each:

How many stars in the universe?

Two trillion (2 x 10^12) galaxies and an average of 100 billion (1 x 10^11) stars per galaxy gives about 2 x 10^23 stars, give or take a few powers of ten:

200,000,000,000,000,000,000,000 stars

How many molecules in 1/5 ounce of water?

6 x 10^23 is Avogadro's number, the number of molecules in a mole of a substance. A mole of water is H2O = 18 g, so 1/3 of a mole would match the star count, and that is 6 cubic cm of water, about 1/5 of an ounce!

This makes me think: our ideas about the origins of the universe, 14 billion years ago, via the Big Bang, have a lot yet to explain. A lot.