The universe is billions of years old.

If, in the future, humanity were to explore the galaxy and visit other planets around other stars, we might be visiting places where at one time, an advanced civilization once existed.

However, if such a civilization existed, it might have been millions of years in the past. If that was the case, how would we even know that it existed?

Also, what if we ask that same question of Earth rather than of alien worlds?

Learn more about the Silurian Hypothesis on this episode of Everything Everywhere Daily.

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