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Comment by chrisfosterelli | Hacker News Reader

This made me think "wow, maybe the universe isn't so big after all", and then I remembered there are somewhere between 200 billion and 2 trillion other galaxies out there.

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a billion billion stars is the same order of magnitude scale as a billion billion seconds, which is about the age of the universe. Or, a billionth billionth second (one attosecind), which is the amount of time it takes for an electron to change orbitals, and also the speed of light across the diameter of a Hydrogen atom.

"which is about the age of the universe" The more I think about the big bang the more it doesn't make sense because it would mean that the universe came out of nothing.

100 billion is the only number in cosmology you need to remember: stars in the milky way, galaxies in the observable universe, and age of the universe (in dog years).

No.

The estimated number of galaxies in the observable universe is between 200 billion and 2 trillion.

https://en.wikipedia.org/wiki/Galaxy

The number of stars in our galaxy is estimated between 100 and 400 billion.

https://en.wikipedia.org/wiki/Milky_Way

What's an order of magnitude between friends?

Clearly you’re not a cosmologist if you care about digits of accuracy ;)

Or 10^10, close enough

That's the "observable" universe. We don't know exactly how big the universe is and whether it has a limited size in the first place.

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