Neocatastrophism is the hypothesis that life-exterminating events such as gamma-ray bursts have acted as a galactic regulation mechanism in the Milky Way upon the emergence of complex life in its habitable zone. [1] [2] [3] It is one of several proposed solutions to the Fermi paradox since it provides a mechanism which would have delayed the advent of intelligent beings in local galaxies near Earth.
It is estimated that Earth-like planets in the Milky Way started forming 9 billion years ago, and that their median age is 6.4 ± 0.7 Ga. [4] Moreover, 75% of stars in the galactic habitable zone are older than the Sun. [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 interstellar travel, (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. [6] This leads to a conundrum first posed in 1950 by the physicist Enrico Fermi in his namesake paradox: "Why are no aliens or their artifacts physically here?" [7]
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 galactic habitable zone. The main proposed regulation mechanism is gamma-ray bursts. [1] [2] [3]
Part of the neocatastrophism hypothesis is that stellar 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 a phase 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.
Astrobiology is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
The Fermi Gamma-ray Space Telescope, formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor, is being used to study gamma-ray bursts and solar flares.
In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth required an improbable combination of astrophysical and geological events and circumstances.
The zoo hypothesis speculates on the assumed behavior and existence of technologically advanced extraterrestrial life and the reasons they refrain from contacting Earth. It is one of many theoretical explanations for the Fermi paradox. The hypothesis states that alien life intentionally avoids communication with Earth to allow for natural evolution and sociocultural development, and avoiding interplanetary contamination, similar to people observing animals at a zoo. The hypothesis seeks to explain the apparent absence of extraterrestrial life despite its generally accepted plausibility and hence the reasonable expectation of its existence. A variant on the zoo hypothesis suggested by the former MIT Haystack Observatory scientist John Allen Ball is the "laboratory" hypothesis, in which humanity is being subjected to experiments, with Earth serving as a giant laboratory.
The Great Filter is the idea that in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
Intergalactic travel is the hypothetical crewed or uncrewed travel between galaxies. Due to the enormous distances between the Milky Way and even its closest neighbors—tens of thousands to millions of light-years—any such venture would be far more technologically and financially demanding than even interstellar travel. Intergalactic distances are roughly a hundred-thousandfold greater than their interstellar counterparts.
Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones (HZ) the only areas in which life might arise.
An Earth analog, also called an Earth analogue, Earth twin, or second Earth, is a planet or moon with environmental conditions similar to those found on Earth. The term Earth-like planet is also used, but this term may refer to any terrestrial planet.
The planetarium hypothesis, conceived in 2001 by Stephen Baxter, attempts to provide a solution to the Fermi paradox by holding that our astronomical observations represent an illusion, created by a Type III civilization capable of manipulating matter and energy on galactic scales. He postulates that we do not see evidence of extraterrestrial life because the universe has been engineered so that it appears empty of other life.
The Eerie Silence: Renewing Our Search for Alien Intelligence is a 2010 popular science book by Paul Davies, chair of the SETI: Post-Detection Science and Technology Taskgroup of the International Academy of Astronautics. The Eerie Silence explores the possibilities of intelligent extraterrestrial life, and its potential consequences.
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 and the rate and density of major catastrophes such as supernovae, and uses these to calculate which regions of a galaxy are more likely to form terrestrial planets, initially develop simple life, and provide a suitable environment for this life to evolve and advance. According to research published in August 2015, very large galaxies may favor the birth and development of habitable planets more than smaller galaxies such as the Milky Way. In the case of the Milky Way, its galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs (33,000 ly) and an inner radius close to the Galactic Center.
Rare Earth: Why Complex Life Is Uncommon in the Universe is a 2000 popular science book about xenobiology by Peter Ward, a geologist and evolutionary biologist, and Donald E. Brownlee, a cosmologist and astrobiologist. The book is the origin of the term 'Rare Earth Hypothesis' which, like the book's authors, assert that complex life is rare in the universe.
The aestivation hypothesis is a hypothesized solution to the Fermi paradox conceived in 2017 by Anders Sandberg, Stuart Armstrong and Milan M. Ćirković. The hypothesis, published on 27 April 2017, suggests advanced alien civilizations may be storing energy and aestivating, until the universe cools to better make use of the stored energy to perform tasks.
Milan M. Ćirković is a Serbian astronomer, astrophysicist, philosopher and science book author. He has worked in the fields of astrobiology, global catastrophic risks and future of humanity where he also co-authored with Nick Bostrom. A focus of his work is the Fermi Paradox for which he has critically discussed existing and also proposed novel solutions.
The following outline is provided as an overview of and topical guide to extraterrestrial life:
The dark forest hypothesis is the conjecture that many alien civilizations exist throughout the universe, but they are both silent and hostile, maintaining their undetectability by humanity for fear of being destroyed by another hostile and undetected civilization. In this framing, it is presumed that any space-faring civilization would view any other intelligent life as an inevitable threat, and thus destroy any nascent life that makes itself known. As a result, the electromagnetic spectrum would be relatively quiet, without evidence of any intelligent alien life, as in a "dark forest" filled with "armed hunter(s) stalking through the trees like ghosts".
The berserker hypothesis, also known as the deadly probes scenario, is the idea that humans have not yet detected intelligent alien life in the universe because it has been systematically destroyed by a series of lethal Von Neumann probes. The hypothesis is named after the Berserker series of novels (1963-2005) written by Fred Saberhagen.
The Hart–Tipler conjecture is the idea that an absence of detectable Von Neumann probes is contrapositive evidence that no intelligent life exists outside of the Solar System. This idea was first proposed in opposition to the Drake equation in a 1975 paper by Michael H. Hart titled "Explanation for the Absence of Extraterrestrials on Earth". The conjecture is the first of many proposed solutions to the Fermi paradox. In this case, the solution is that there is no other intelligent life because such estimates are incorrect. The conjecture is named after astrophysicist Michael H. Hart and mathematical physicist and cosmologist Frank Tipler.
| Programs | |
|---|---|
| Messages | |
| People | |
| Other | |
