Neocatastrophism is the

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

that life-exterminating events such as

gamma-ray burst In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milli ...

s have acted as a galactic regulation mechanism in the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

upon the emergence of complex

life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...

in its

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kas ...

.Cirković MM, Vukotić B. (2008). Astrobiological phase transition: towards resolution of Fermi's paradox. Orig Life Evol Biosph. 38(6):535-47. Ćirković M.M. (2009)
Fermi's paradox: The last challenge for copernicanism?
Serbian Astronomical Journal 178:1-20 Cirkovic, M. M. Vukotic, B. (2009)
Astrobiological Landscape and Neocatastrophism.
Publications of the Astronomical Observatory of Belgrade,86:193-19 It is one of several proposed solutions to the

Fermi paradox The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high a priori likelihood of its existence, and by extension of obtaining such evidence. As a 2015 article put it, ...

since it provides a mechanism which would have delayed the advent of intelligent beings in local galaxies near

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

The problem

It is estimated that Earth-like

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

s in the Milky Way started forming 9 billion years ago, and that their

median In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic fe ...

age is 6.4 ± 0.7 Ga. Moreover, 75% of stars in the

galactic habitable zone In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life might most likely develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity (the presence of elem ...

are older than the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. 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

interstellar travel Interstellar travel is the hypothetical travel of spacecraft from one star system, solitary star, or planetary system to another. Interstellar travel is expected to prove much more difficult than interplanetary spaceflight due to the vast dif ...

, (even of the "slow" kind that is nearly within the reach of present Earth technology) could in theory, if it had arisen elsewhere, take only 5 to 50 million years to colonize the galaxy.Crawford, I.A.
"Where are They? Maybe we are alone in the galaxy after all"
, '' Scientific American,'' July 2000, 38-43, (2000) This leads to a conundrum first posed in 1950 by the physicist

Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...

in his namesake paradox: "Why are no aliens or their artifacts physically here?"Webb S. (2002). ''If the universe is teeming with aliens, where is everybody? Fifty solutions to the Fermi paradox and the problem of extraterrestrial life''. Copernicus Books (Springer Verlag)

The neocatastrophism resolution

The hypothesis posits that astrobiological 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 the

. The main proposed regulation mechanism is gamma-ray bursts. Part of the neocatastrophism hypothesis is that

stellar evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...

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, this creates the possibility of a

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of ...

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.

References

{{Extraterrestrial life, state=expanded Astrobiology Extraterrestrial life Origin of life Fermi paradox Biological hypotheses Disasters Astronomical controversies Astronomical hypotheses Gamma-ray bursts

The problem

The neocatastrophism resolution

See also

References