New research suggests that technological civilizations in the Milky Way are extremely rare, with the closest potentially 33,000 light-years away.
According to new research, the nearest technological civilization in the Milky Way might be as far as 33,000 light-years from Earth. For such a species to exist during the same era as humanity, their civilization would need to have survived for at least 280,000 years, and potentially for millions of years.
These findings highlight how unlikely it is to discover planets that mirror Earth, with both active plate tectonics and an atmosphere rich in nitrogen and oxygen, balanced by just the right proportions of oxygen and carbon dioxide.
Taking these requirements into account, the outlook for SETI (Search for Extraterrestrial Intelligence) appears discouraging, say Dr. Manuel Scherf and Professor Helmut Lammer of the Space Research Institute at the Austrian Academy of Sciences in Graz.
The Carbon Dioxide Balance
The more carbon dioxide a planet has in its atmosphere, the longer it can sustain a biosphere and photosynthesis for, and prevent the atmosphere from escaping into space, but it’s a careful balance: too much carbon dioxide and it can lead to a runaway greenhouse effect, or render the atmosphere too toxic for life.
Plate tectonics regulates the amount of carbon dioxide in the atmosphere as part of the carbon-silicate cycle, and so a habitable planet requires plate tectonics. Gradually, though, the carbon dioxide that is drawn out of the atmosphere gets locked away in rocks rather than recycled.
