The idea that life originated on another planet and was transported to Earth. It’s difficult to prove or disprove in a similar way to the Silurian hypothesis, evidence is difficult to obtain—artifacts from civilizations don’t last that long, evidence of life is not visible on any likely originating planet within our solar system.
See also:
- An extraterrestrial body like Oumuamua could fit
Links to this note
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Frequency Range of Hearing Is Probably the Same in the Universe
Organisms evolving independently on different planets will probably end up with the ability to hear things at the same frequency range as humans. That’s because the sound a predator makes as it approaches would be in the same spectrum regardless of atmosphere. Organisms that could react to these frequencies would have an advantage and survive.