Universe, Earth, and Life on Earth
| Universe Age: | 13.72 billion years |
| Number of Galaxies in Universe: | 170 billion |
| Number of Stars within a Galaxy: | 10 million (10**7) to 100 trillion (10**14) |
| Total Number of Stars in Universe: | 17 x 10**17 to 17 x 10**24 |
| Formulation of The Milky Way: | 13.2 billion years ago |
| Formulation of our Solar System: | 4.568 billion years ago |
| Formulation of the Earth: | 4.54 billion years ago |
| Life on Earth, most elemental: | 3.8 billion years ago |
| Life on Earth, fish transition from water to land, e.g. Tiktaalik: |
375 million years ago |
| Life on Earth, Dinosaurs extinct: | 65.5 million years ago |
| Life on Earth, Homo sapiens existence: | 200,000 years ago |
| Life on Earth, current number of species: | 1.5 million known; 2 million to 100 million estimated |
| Life on Earth, extinct species: | 99.9% of all species that ever existed |
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