# How big, how far is the universe?

There are more stars in our Universe than there are grains of sand on all the beaches on Earth.” There are 100 to 400 billion stars in the Milky Way and more than 100 billion galaxies in the Universe – maybe as many as 500 billion. If you multiply stars by galaxies, at the low end, you get 10 billion billion stars, or 10 sextillion stars in the Universe – a 1 followed by 22 zeros. At the high end, it’s 200 sextillion.

# The numbers

These are mind bogglingly huge numbers. How do they compare to the number of grains of sand on the collective beaches of an entire planet? This type of sand measures about a half millimeter across.

# The sand grains

You could put 20 grains of sand packed in side-by-side to make a centimeter. 8000 grains in one cubic centimeter. If you took 10 sextillion grains of sand, put them into a ball, it would have a radius of 10.6 kilometers. And for the high end of our estimate, 200 sextillion, it would be 72 kilometers across. If we had a sphere bigger than the Earth, it would be an easy answer, but no such luck. This might be close.

So, is there that much sand on all the beaches, everywhere, on this planet? You’d need to estimate the average volume of a sandy beach and the average amount of the world’s coastlines which are beaches.

The estimates and calculations made by Dr. Jason Marshall, aka, the Math Dude are that, there about 700 trillion cubic meters of beach of Earth, and that works out to around 5 sextillion grains of sand.