Neocatastrophism is thehypothesis that life-exterminating events such asgamma-ray bursts have acted as a galactic regulation mechanism in theMilky Way upon the emergence of complexlife in itshabitable zone.[1][2][3] It is one of several proposed solutions to theFermi paradox since it provides a mechanism which would have delayed the advent ofintelligent beings in local galaxies nearEarth.
It is estimated that Earth-likeplanets in the Milky Way started forming 9 billion years ago, and that theirmedian age is 6.4 ± 0.7Ga.[4] Moreover, 75% of stars in thegalactic habitable zone are older than theSun.[5] This makes the existence of potential planets with evolved intelligent life more likely than not to be older than that of the Earth (4.54 Ga). This creates an observational dilemma since even slower-than-lightspeedinterstellar travel could in theory take only 5 to 50 million years to colonize the galaxy.[6] This leads to a conundrum first posed in 1950 by the physicistEnrico Fermi inhis namesake paradox: "Why are no aliens or their artifacts physically here?"[7]
The hypothesis posits thatastrobiological evolution is subject to regulation mechanisms that arrest or postpone the advent of complex creatures capable of interstellar communication and traveling technology. These regulation mechanisms act to temporarily sterilize planets of biology in thegalactic habitable zone. The main proposed regulation mechanism is gamma-ray bursts.[1][2][3]
Part of the neocatastrophism hypothesis is thatstellar evolution produces a decreasing frequency of such catastrophic events increasing the length of the "window" in which intelligent life might arise as galaxies age. According to modeling,[1][2][3] this creates the possibility of aphase transition at which point a galaxy turns from a place that is essentially dead (with a few pockets of simple life) to one that is crowded with complex life forms.
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