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Loud Aliens Model
editThe Loud Aliens Model is a proposed theoretical model to predict when humanity will find signs of extraterrestrial life, as well as to model the behavior of these civilization. It uses various criteria to determine the probability that we will encounter an aggressively expanding extraterrestrial civilization. Originally proposed by Stephan Jay Olson in 2015, there have been seven[1] total papers relating to this topic, of which four have been published. What differentiates this model from other predictions, such as the ones made by the Drake Equation, is that it predicts the appearance of "loud" civilizations, or civilizations that will expand and alter the space around them in a significant way (similar to a Kardashev type III civilization).[2]
Types of aliens described in the model
editIn the model, alien civilizations are classified in two broad categories: Loud Aliens and Quiet Aliens. These categories, while not originally named by S. Jay Olsen, were designed to classify whether a civilization satisfied the Loud Aliens Model or not.
Quiet Aliens
editQuiet Alien Civilizations consist of civilizations that do not make significant changes to the space they occupy, as well as that they have not expanded beyond their planet of origin. These civilizations are best modeled by the Drake Equation, since there is currently no way to observe these directly.
Loud Aliens
editLoud Aliens are those that have developed interstellar travel, as well as made noticeable changes to their territory. These civilizations are expected to expand aggressively into unoccupied space, only stopping when encountering another Loud Alien civilization.
Grabby Aliens Model
editFirst described by Robin Hanson, this model attempts to simplify many of the criteria of the Loud Aliens Model. It does so by using three main assumptions (all based on observations of humanity as an example): rate of birth of a Grabby Civilization, rate of expansion, and number of hard steps[3] to determine the growth of an alien civilization.
Key assumptions
editRate of birth
editThe model assumes that a civilization similar to humanity will become a grabby civilization within 10 million years.[3]
Rate of expansion (s)
editThis variable is measured as a fraction of the speed of light (c).
The model suggests that, due to the selection effect caused by the fact that humanity has yet to observer signs of another civilization, there is reason to believe that the rate of expansion is very high. Using our current technology and the fact that the speed of light is finite, we can see a certain amount of time into the past, and as such we should be able to notice any grabby civilizations making changes to their surroundings. Yet the data suggest that there have been no sightings of such civilizations, resulting in the estimate for the rate of expansion to be high, as to allow the civilization to have time to grow without being noticed.[3]
Hard steps (n)
editThe model goes over various possible values for the number of hard steps that an average civilization will have to go through to become grabby, resulting in a value of 6 from a range of 3 to 12 hard steps.[3]
References
edit- ^ "Grabby Aliens – a simple model by Robin Hanson". grabbyaliens.com. Retrieved 2021-11-26.
- ^ Olson, S. Jay (2016-04-05). "Estimates for the number of visible galaxy-spanning civilizations and the cosmological expansion of life". International Journal of Astrobiology. 16 (2): 176–184. doi:10.1017/s1473550416000082. ISSN 1473-5504.
- ^ a b c d Hanson, Robert; Martin, Daniel; McCarter, Calvin; Paulson, Jonathan (September 7, 2021). "If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare" (PDF). ArXiv. Retrieved November 29, 2021.
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