Our existence here is proof enough that it can happen. We can imagine that if life comes to exist anywhere else in the Universe, there are three different levels it could achieve:
- Life begins on a world, but doesn’t last, thrive, or continue in perpetuity.
- Life thrives, sustains, and lasts billions of years, where it causes substantial changes to the surface properties of the world where it exists.
- Life becomes intelligent, technologically advanced, and either communicative, spacefaring, or both.
Clearly, the more advanced possibilities are more exciting, but also likely to be more rare. Yet sometimes the rare things are the easiest to find because they stand out so spectacularly against everything else that’s there.
Although it’s just conjecture at this point, scientists speculate that life in the Universe is probably common, with the ingredients and opportunities for it to arise appearing practically everywhere. Life that thrives and sustains itself on a world, to the point where it can change its atmospheric and/or surface properties, may need to get lucky, and is likely more uncommon. Evolving to become complex, differentiated, multicellular creatures is likely even rarer.
No matter which method pays dividends first, it will be among the greatest day in the history of life on Earth.
Editor’s note: Ethan Siegel is a PhD astrophysicist
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