10⁹ Years; geological unit of time.
1 Links: Did Andromeda crash into the Milky Way 10 billion years ago?
2 In other words: It's hard to debug 3 billion years of evolution.
3 More than two billion years ago, sand settled on the ocean floor.
4 We've had like a stable amount for the last several billion years .
5 And Earth will probably be habitable for another billion years or so.
6 After all, life did perfectly well for three billion years without them.
7 The Sun is a fairly young star, only five billion years old.
8 A hint at what was to befall in a few billion years .
9 For two billion years bacterial organisms were the only forms of life.
10 Twenty million years feels short when it is half a billion years ago.
11 Four billion years later people began to wonder how it had all happened.
12 Estimates run from forty billion years to one hundred billion years .
13 And four billion years ago, Earth was frequently struck by meteors.
14 The company says fusion could eventually supply a billion years worth of electricity.
15 Once, we were assured that it would take five billion years to happen.
16 But rest assured, that won't happen for another six billion years or so.
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