Topics: Fermi Paradox, Planetary Science, Space Exploration, SETI
Well, this is news! Tipler in particular kind of (ahem), went over the edge in the theory world, and thus everyone kind of treats him like your very strange uncle. He apparently plays in the story of the Fermi Paradox that wasn't...
If Fermi wasn't the source of this pessimistic idea, where did it come from?
The notion “... they are not here; therefore they do not exist” first appeared in print in 1975, when astronomer Michael Hart claimed that if smart aliens existed, they would inevitably colonize the Milky Way. If they existed anywhere, they would be here. Since they aren’t, Hart concluded that humans are probably the only intelligent life in our galaxy, so that looking for intelligent life elsewhere is “probably a waste of time and money.” His argument has been challenged on many grounds—maybe star travel is not feasible, or maybe nobody chooses to colonize the galaxy, or maybe we were visited long ago and the evidence is buried with the dinosaurs—but the idea has become entrenched in thinking about alien civilizations.
In 1980, the physicist Frank Tipler elaborated on Hart’s arguments by addressing one obvious question: where would anybody get the resources needed to colonize billions of stars? He suggested “a self-replicating universal constructor with intelligence comparable to the human level.” Just send one of these babies out to a neighboring star, tell it to build copies of itself using local materials, and send the copies on to other stars until the Galaxy is crawling with them. Tipler argued that absence of such gizmos on Earth proved that ours is the only intelligence anywhere in the entire Universe—not just the Milky Way galaxy—which seems like an awfully long leap from the absence of aliens on our one planet.
Hart and Tipler clearly deserve credit for the idea at the heart of the so-called Fermi paradox. Over the years, however, their idea has been confused with Fermi’s original question. The confusion evidently started in 1977 when the physicist David G. Stephenson used the phrase ‘Fermi paradox’ in a paper citing Hart’s idea as one possible answer to Fermi’s question. The Fermi paradox might be more accurately called the ‘Hart-Tipler argument against the existence of technological extraterrestrials’, which does not sound quite as authoritative as the old name, but seems fairer to everybody.
Scientific American: The Fermi Paradox Is Not Fermi's, and It Is Not a Paradox
Robert H. Gray
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