On the clearest night, the human eye can only see about 3,000 stars, when there are an estimated 100,000,000,000 in our galaxy alone! But our universe consists of more than 100 billion galaxies, and each galaxy, on average contains more that 100 billion stars, which accounts for more than 10 billion trillion stars! So, if the number of stars in the universe is estimated to be greater than the number of grains of sand on all the beaches in the world, it means that on a clear night, we can see only the equivalent of a handful of sand.
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via: [Meemilet 1.1.1]: