Belting Away

Searching for extraterrestrial life has recently won its spurs in the scientific establishment--recently in this case being within the latest decade or so. That has to do with the increased ability to gather evidence bearing on the subject. Collecting evidence is what separates scientific inquiry from simple, if interesting, speculation. Within a decade or two, we have found planets orbiting other stars, good evidence for the existence of a huge water ocean under the ice of Jupiter's moon, Europa, and a meteor from Mars that may or may not contain evidence of Martian life.

Scientists have come up with a theory to guide the search for life in the universe. Called variously the "Life" or "Green" Belt theory, it points out that there is a belt around every normal star in which temperatures would be right for the existence of life as we understand it. Around smal, dim red dwarfs, that belt is extremely narrow, but would last billions and billions of years. Around huge, bright blue giants that burn through their nuclear fuel quickly, the life belt is broad, but short-lived. There's almost certainly not enough time for life to develop on a planet orbiting a blue giant before the star goes nova. Not surprisingly-- really, basically by definition-- the stars most likely to support life and civilizations under this theory are stars most like our Sun.

So, the search for civilizations should concentrate on stars like ours, right? Perhaps. If we assume interstellar travel is impossible, that conclusion would be, well, conclusve. If we allow for the possibility of immensely wealthy, advanced, long-lived civilizations mastering interstellar flight, however, things might change. A blue giant might be a good place to plant an energetic group. A close orbit around a red dwarf might be ideal for a civilization that had developed elsewhere. Life in life belts may be more abundant than we realize.