“I’ve heard that there are more stars in our Universe than there are grains of sand on all the beaches on Earth. Is this possible?” Awesome question, and a great excuse to do some math.
.. 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.
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.
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. {6. miles} And for the high end of our estimate, 200 sextillion, it would be 72 kilometers across. {45 miles}
When it comes to atoms ...a single grain of sand has more atoms than there are stars in the Universe.
A point which is returned to later is that at least some of the billions of stars will have orbiting planets, even moons, which might accommodate life, even intellligent life.
When you read about them you realise that it will be thousands, perhaps millions of years before humanity could travel the distances involved.
