View source for Rio scale

{{Short description|Measure for extraterrestrial intelligence events}}

The '''Rio scale''' was proposed in 2000 as a means of quantifying the significance of a [[Search for extraterrestrial intelligence|SETI]] detection.<ref>{{Cite web |title=The Rio Scale |url=https://iaaspace.org/wp-content/uploads/iaa/Scientific%20Activity/setirio.pdf}}</ref><ref>{{Cite magazine |last=Arbesman |first=Samuel |title=Quantifying Alien Encounters: The Rio Scale |language=en-US |magazine=Wired |url=https://www.wired.com/2012/02/quantifying-alien-encounters-the-rio-scale/ |access-date=2022-05-30 |issn=1059-1028}}</ref> The scale was designed by [[Iván Almár]] and [[Jill Tarter]] to help tell policy-makers how likely, from 0 to 10, it is that an extraterrestrial radio signal has been produced by an intelligent civilization.<ref name="scientificamerican-20">{{Cite web |last=Bartels, SPACE.com |first=Meghan |title=To Fight Fake News, SETI Researchers Update Alien-Detection Scale |url=https://www.scientificamerican.com/article/to-fight-fake-news-seti-researchers-update-alien-detection-scale/ |access-date=2022-05-30 |website=Scientific American |language=en}}</ref>

The scale is inspired by the [[Torino scale]], which is used to determine the impact risk associated with [[near-Earth objects]]. Just as the Torino scale takes into account how significant an object's impact on the planet would be, the Rio scale takes into account how much a public announcement of the discovery of extraterrestrial intelligence would probably impact society.

The [[International Academy of Astronautics|IAA]] SETI Permanent Study Group officially adopted the Rio scale as a way of bringing perspective to claims of [[extraterrestrial intelligence]] (ETI)  detection, and as an acknowledgement that even false ETI detections may have disastrous consequences.<ref>{{Cite web |title=How can you tell if that ET story is real? St Andrews scientists revise the Rio Scale for alien encounters |url=https://www.seti.org/press-release/how-can-you-tell-if-et-story-real-st-andrews-scientists-revise-rio-scale-alien-encounters}}</ref><ref>{{Cite web |last=Hall |first=Shannon |title=Strange signals from 234 stars could be ET - or human error |url=https://www.newscientist.com/article/2109139-strange-signals-from-234-stars-could-be-et-or-human-error/ |access-date=2022-05-30 |website=New Scientist |language=en-US}}</ref>

The scale was modified in 2011 to include a consideration of whether contact was achieved through an interstellar message or a physical extraterrestrial artifact, including all indications of intelligent extraterrestrial life such as [[technosignature]]s.<ref>{{Cite web |author1=Mike Wall |date=2016-10-28 |title=Mysterious Star Pulses May Be Alien Signals, Study Claims |url=https://www.space.com/34541-alien-life-search-possible-seti-signals.html |access-date=2022-05-30 |website=Space.com |language=en}}</ref> A 2.0 version of the scale was proposed in 2018.<ref name="scientificamerican-20" /><ref>{{cite news |last1=Tudhope |first1=Christine |title=Scientists revise the Rio Scale for reported alien encounters |url=https://phys.org/news/2018-07-scientists-rio-scale-alien-encounters.html |access-date=18 September 2022 |work=phys.org |ref=phys-20 |language=en}}</ref><ref>{{cite news |last1=Bartels |first1=Meghan |title=SETI Researchers Want to End the Alien-Detection Hype |url=https://www.space.com/41327-seti-alien-signals-hype-richter-scale.html |access-date=18 September 2022 |work=Space.com |date=31 July 2018 |ref=spacecom-20 |language=en}}</ref>

== Calculation ==

In its 2.0 version, the Rio Scale, '''R''', of a given event is calculated as the product of two terms.<ref>{{cite journal |last1=Forgan |first1=Duncan |last2=Wright |first2=Jason |last3=Tarter |first3=Jill |last4=Korpela |first4=Eric |last5=Siemion |first5=Andrew |last6=Almár |first6=Iván |last7=Piotelat |first7=Elisabeth |title=Rio 2.0: revising the Rio scale for SETI detections |journal=International Journal of Astrobiology |date=August 2019 |volume=18 |issue=4 |pages=336–344 |doi=10.1017/S1473550418000162|bibcode=2019IJAsB..18..336F |hdl=10023/16927 |hdl-access=free }}</ref>

:<math> R = Q\delta</math>

The first term, '''Q''', is the significance of the consequences of an event. It is determined considering three factors: the estimated distance to the source of the signal (a value between 0 and 4), the prospects for communicating with the source (a value between 0 and 4) and how likely is that the sender is aware of humanity (a value between -1 and 2). The value of each factor is determined by answering a question and Q is calculated by summing the three values.

The second term, '''δ''', is the probability that the event actually occurred. Its value is determined by first calculating a term, '''J''', based on three factors: the probability that the signal is real, the probability that it is not instrumental, and the probability that it is not natural or human-made. The values for these factors are determined by answering a questionnaire and J is calculated by summing them. δ is then calculated using the formula {{math|''&delta;'' {{=}} 10{{sup|(10-J)/2}}}}.

The final R value, going from 0 to 10, is the likelihood that the observed event was produced by an intelligent civilization.

== Rating scale ==
{| class="wikitable"
|-
! Rio value !! Importance
|-
| 10 || Extraordinary
|-
| 9 || Outstanding
|-
| 8 || Far-reaching
|-
| 7 || High
|-
| 6 || Noteworthy
|-
| 5 || Intermediate
|-
| 4 || Moderate
|-
| 3 || Minor
|-
| 2 || Low
|-
| 1 || Insignificant
|-
| 0 || Nil
|}

== See also ==
* [[Quiet and loud aliens]]
* [[San Marino Scale]]

== References ==
{{Reflist}}

{{Extraterrestrial life}}

{{Interstellar messages}}

[[Category:Search for extraterrestrial intelligence]]
[[Category:Extraterrestrial life]]
[[Category:Interstellar messages]]


{{astrobiology-stub}}