Scientists and philosophers have been attempting to define life for ages. In biology class we were taught to define life through the set of features that we, and every other species on the planet share. Things like movement, respiration, growth, and reproduction. Life is made of cells and has DNA. But does biochemistry constitute the whole picture? As far back as 1970, Carl Sagan didn’t think so. Attempts at defining life, he and many others thought, were too constrained by the characteristics of life as we know it. A single example of extraterrestrial life could change everything.
Employing an elegant music metaphor, Sagan wrote, “It is not known whether there is a vast array of biological themes and counterpoints in the universe; whether there are places that have fugues, compared with which our one tune is a bit thin and reedy. Or it may be that our tune is the only tune around. Accordingly, the prospects for life on other planets must be considered in any general discussion of life.
Today a new generation of astrobiologists have taken Sagan’s prospect to heart. If life has managed to gain a foothold somewhere else in the cosmos, alien life could look very different than the varieties of life found on Earth. If we don’t have a broad, robust definition of what life is, we may miss it when searching for extraterrestrial life in the cosmos.
To read more, click here.