We have only one example of biology forming in the universe ' life on Earth. But what if life can form in other ways' How do you look for alien life when you don't know what alien life might look like' These questions are preoccupying astrobiologists, who are scientists who look for life beyond Earth. Astrobiologists have attempted to come up with universal rules that govern the emergence of complex physical and biological systems both on Earth and beyond. I'm an astronomer who has written extensively about astrobiology. Through my research, I've learned that the most abundant form of extraterrestrial life is likely to be microbial, since single cells can form more readily than large organisms. But just in case there's advanced alien life out there, I'm on the international advisory council for the group designing messages to send to those civilizations. Many of these exoplanets are small and rocky, like Earth, and in the habitable zones of their stars. The habitable zone is the...
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