Is it true? Probably not, but it depends on a lot of assumptions you have to make, some of which are hard to pin down.
Generally, when astronomers broadly estimate things, we like to be accurate to within a factor of 10, meaning the number we get is within one-tenth to 10 times bigger than the true answer.
It's actually rather hard to nail that number down because we sit in the Milky Way and it's hard to count stars from within the thick of them.
So what about the sand on Earth?
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