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  • Cited by 2
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    This article has been cited by the following publications. This list is generated based on data provided by CrossRef.

    Korbitz, Adam 2014. Toward understanding the active SETI debate: Insights from risk communication and perception. Acta Astronautica, Vol. 105, Issue. 2, p. 517.

    Neal, Mark 2014. Preparing for extraterrestrial contact. Risk Management, Vol. 16, Issue. 2, p. 63.


The game of active search for extra-terrestrial intelligence: breaking the ‘Great Silence’

  • Harold P. de Vladar (a1)
  • DOI:
  • Published online: 06 November 2012

The search for extra-terrestrial intelligence (SETI) has been performed principally as a one-way survey, listening of radio frequencies across the Milky Way and other galaxies. However, scientists have engaged in an active messaging only rarely. This suggests the simple rationale that if other civilizations exist and take a similar approach to ours, namely listening but not broadcasting, the result is a silent universe. A simple game theoretical model, the prisoner's dilemma, explains this situation: each player (civilization) can passively search (defect), or actively search and broadcast (cooperate). In order to maximize the payoff (or, equivalently, minimize the risks) the best strategy is not to broadcast. In fact, the active search has been opposed on the basis that it might be dangerous to expose ourselves. However, most of these ideas have not been based on objective arguments, and ignore accounting of the possible gains and losses. Thus, the question stands: should we perform an active search? I develop a game-theoretical framework where civilizations can be of different types, and explicitly apply it to a situation where societies are either interested in establishing a two-way communication or belligerent and in urge to exploit ours. The framework gives a quantitative solution (a mixed-strategy), which is how frequent we should perform the active SETI. This frequency is roughly proportional to the inverse of the risk, and can be extremely small. However, given the immense amount of stars being scanned, it supports active SETI. The model is compared with simulations, and the possible actions are evaluated through the San Marino scale, measuring the risks of messaging.

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I. Almár (2011). SETI and astrobiology: the Rio Scale and the London Scale. Acta Astronaut. 69(910), 899904.

I. Almár & H.P. Shuch (2007). The San Marino Scale: a new analytical tool for assessing transmission risk. Acta Astronaut. 60(1), 5759.

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J. Welch (2009). The Allen telescope array: the first widefield, panchromatic, snapshot radio camera for radio astronomy and SETI. Proc. IEEE, 97(8), 14381447. doi:10.1109/JPROC.2009.2017103.

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International Journal of Astrobiology
  • ISSN: 1473-5504
  • EISSN: 1475-3006
  • URL: /core/journals/international-journal-of-astrobiology
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