The Rio scale was proposed in 2000 as a means of quantifying the significance of a
SETI
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other p ...
detection. The scale was designed by
Iván Almár
Iván Almár (born April 21, 1932 in Budapest) is a Hungarian astronomer. He proposed the San Marino Scale as a means of assessing risks related to extraterrestrial communication. Almár also serves on the Advisory Council of METI (Messaging ...
and
Jill Tarter
Jill Cornell Tarter (born January 16, 1944) is an American astronomer best known for her work on the search for extraterrestrial intelligence (SETI). Tarter is the former director of the Center for SETI Research, holding the Bernard M. Oliver Cha ...
to help policy-makers how likely, from 0 to 10, is that an extraterrestrial radio signal has been produced by an intelligent civilization.
The scale is inspired by the
Torino scale
The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets.
It is intended as a communication tool for astronomers and the public to assess the seriousness of collision pre ...
, which is used to determine the impact risk associated with
near-Earth objects
A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...
. 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 IAA SETI Permanent Study Group officially adopted the Rio scale as a way of bringing perspective to claims of
extraterrestrial intelligence
Extraterrestrial intelligence (often abbreviated ETI) refers to hypothetical intelligent extraterrestrial life. The question of whether other inhabited worlds might exist has been debated since ancient times. The modern form of the concept emerged ...
(ETI) detection, and as an acknowledgement that even false ETI detections may have disastrous consequences.
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
Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not. ...
s. A 2.0 version of the scale was proposed in 2018.
Calculation
In its 2.0 version, the Rio Scale, R, of a given event is calculated as the product of two terms.
:
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 .
The final R value, going from 0 to 10, is the likelihood that the observed event was produced by an intelligent civilization.
Rating scale
See also
San Marino Scale
The San Marino Scale is a suggested scale for assessing risks associated with deliberate transmissions from Earth aimed to possible extraterrestrial intelligent life. The scale evaluates the significance of transmissions from Earth as a function ...
References
Search for extraterrestrial intelligence
Extraterrestrial life
Interstellar messages
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