The Papers

These are the papers we read and/or discussed in the class.  Some are classics and could be considered part of the SETI “canon”, some are latest research that may enter the canon someday, and a few are well known but actually assigned as cautionary tales. Also included are many tangents that follow discussions that came up in class, and were not assigned but are included for additional reading and/or amusement by interested students.

Not all of these papers are publicly available, but most are available through a university library subscription to major journals.  Some are hard to find at all, even with a library as extensive as Penn State’s (we found ILIAD very useful for digging up rare titles).

Those that we assigned in class are in bold.  Some important papers were added to the list after class ended for completeness.

Beneath the titles are a brief description of why that particular entry is relevant to this course, followed by a public link to the citation. Beneath those are links to select blog entries by the 2018 SETI course students that summarize/describe/critique those papers. (You can read all of the entries here.)

These are not presented in the order we followed in class; they are in a more natural order that will be approximated in the 2020 instance of the course.

The instructor thanks Jill Tarter, Shelley Wright, Andrew Howard, Paul Horowitz, Andrew Howard, and the students in the class for helping identify the papers in this list.  If you have big papers that are missed, please email your suggestions to us at and copy Alan Reyes at, who is compiling a comprehensive bibliography of SETI and put much of this page together.

For those of the following articles that have a presence on the NASA ADS, you can find a publicly accessible library put together by Alan Reyes here for ease of viewing and manipulation:


Cocconi & Morrison (1959)
– The birth of Radio SETI.

Bracewell (1960)
– The birth of Artifact SETI.

Drake (1961)
– The first Radio SETI Experiment.
– Kanodia
– Sheihk 

SETI Pessimism

Hart (1975)
– The first sharpening and an early formal statement of the Fermi paradox.

Tipler (1980)
– Arguments against there being ETI. An argument against the plurality of inhabited worlds.

Brin (1983)
– A trenchant articulation of the Fermi Paradox

Ball (1973)
– An early attempt to resolve the Fermi Paradox: The Zoo Hypothesis

Tipler (1981b)
– A brief history of SETI.

Tipler (1981c)
– Additional remarks on SETI.

Tipler (1993)
– Is SETI a waste of effort?

SETI Optimism & politics

Sagan Petition
– A call for an international observational effort to conduct radio SETI experiments.

Tarter (1985)
– Rebuttal to pessimists, “why radio?”, and the Cosmic Haystack

Ćirković (2018)
– A rebuttal to “intelligence is rare” arguments.

Gray (2015)
– The Fermi Paradox is falsely attributed and isn’t really a formal paradox.

Sagan & Newman (1982)
– A critique of “solipsist” approaches to the ETI question and an analysis of galactic diffusion.

Garber (1999)
– A historical review of the cancellation of SETI funding by NASA.

Wright (2018)
– Argument to the National Academies of Science that SETI is part of Astrobiology and should be funded by NASA

Radio SETI

Bell and Little Green Men
– The discovery of pulsars (which were originally codenamed Little Green Men based on their regular pulsation and potentially artificial origin). Also, an anecdote on the challenges of being a female scientist in a male-dominated Academia.

Oliver (1979)
– The suggestion of a communal “water hole” frequency range that all water-based life would recognize.…6…71O

Kraus (1979)
– The Wow! Signal.…1…31K

Tarter (2001)
– A review of field of SETI from its context in the astronomical and greater scientific landscape, with a look at what has been accomplished and what still needs to be done in Radio SETI.

Purcell (1960)
– A nice summary of the early justification for radio SETI.;view=1up;seq=3

Oliver (1974)
– A nice summary of how radio SETI works.…2…11O

Drake (1965)
– The proper citation to the Drake Equation
– F. Drake, “The Radio Search for Intelligent Extraterrestrial Life.” In Current Aspects of Exobiology, ed. G. Mamikunian and M. H. Briggs, 323-45. Oxford University Press

Sullivan, Brown and Weatherill (1978)
–  “Eavesdropping – The radio signature of the earth”
– A discussion on how obvious Earth is in radio and of what we can infer about a planet from an “eavesdropping” detection without any decoding of information content.

More on Wow!

Gray (1994)
– Searching for the Wow! locale.

Gray (2001)
– A later search for Wow! using the VLA.…546.1171G

Gray (2002)
– A search for periodic emissions near the Wow! locale.…578..967G

Gray (2011)
– Supplemental reading for Wow!

Schelling Points and beacons

Dixon (1973)
– “Beacons” and “anti-cryptography” in SETI

In-class activity
An exercise to get students thinking about Schelling points.

Schelling (1960) The Strategy of Conflict, Chapter 4
– On the theory of cooperation and the the introduction of Schelling points, common places or times of opportunity recognized by both parties in their pursuit of finding one another.

Alexander (2012)
– A nice popular description of Schelling points.

Dixit (2012)
– The Art of Strategy, Chapter 4: A Beautiful Equilibrium, p. 110: Lost in New York

ABC Primetime
– A video of the Schelling Experiment in NYC.

Wright et al. (2016) (section 5)
– Analysis of how to distinguish beacons from other signals in SETI…816…17W

Wright (2017; Web)
– Popular description of Schelling Points

Wright (2017)
– Schelling points in SETI


The Arecibo Message
– The first METI message, sent from Arecibo in 1974.

METI Letter
– A statement encouraging international discussion on METI.

Gertz (2016)
– A condemnation of the activity and proponents of METI.

Wright (2017)
–  An ethical consideration of METI -Sheikh

– An anthropologist considers how humanity looks from the outside

Shostak (2015)
– METI is not Dangerous

– Waiting for Extraterrestrial Intelligence?

JBIS Volume 67, especially Shostak pp 41-42
– Shostak responds to Brin and other METI opponents

Denning (2010)
Unpacking the great transmission debate


Schwartz & Townes (1961)
– The suggestion that stimulated emission in the optical and NIR may be a viable platform to conduct SETI searches.

Wright (2014)
– The instrument design and search strategy of SETI search using pulsed laser signals at NIR wavelength

Optical SETI

Howard et al. (2004)
– An optical SETI search done right.…613.1270H
– Reyes

Kipping & Teachey (2016)
– The proposal that ETIs may seek to cloak the presence of their planet’s transit with deliberate laser emission. Perhaps more importantly: a new Schelling point in SETI.

What frequencies?

Townes (1983)
– A suggestion that searches shouldn’t be limited to radio and microwave and that other wavelength ranges, such as the IR, should be tried.…80.1147T

Hippke & Forgan (2017)
– An analysis of the physical optimum of interstellar communcation.

Other carriers

Harwit (2003)
– The suggestion that photon orbital angular momentum can be a communication way for SETI.

Hippke (2017) – The consideration of alternative carriers to photons, such as subatomic particles and bosons.

Benford (2010) – The consideration of a gravitational wave based SETI message.

Dyson (1963) “Gravitational Machines” in Interstellar Communication: The Search for Extraterrestrial Life; A Collection of Reprints and Original Contributions ed. A.G.W. Cameron
– Gravitational wave detectors should look for evidence of ETIs

Jackson & Benford (2018) — A Gravitational Wave Transmitter

SS artifacts

Freitas (1983)
– The case is made for a search program for extratterestrial messenger probes in the vicinity of the Earth-Moon system.

Carlotto (1988)
– A digital analysis of the “Face” on Mars. A case of SETI done wrong.

Carlotto (1997)
– More face-on-Mars from Carlotto

Freitas (1980)
– A rare search for free-floating Solar System artifacts

Haqq-Misra & Kopparapu (2012)
– An examination of the likelihood of non-terrestrial artifacts in the Solar System.

Davies & Wagner (2013)
– An overview of the strategies used to determine whether the moon had been occupied in the remote past by an ETI.
– Cañas

Rein (2018)
– Analysis of the lifetime of an artificial object in the Solar System: a Tesla Roadster

Kaku (2017)
– Example of radar used to detect (natural) subsurface cavities on other words.

Carter (2009)
– More examples of radar detection of (natural) subsurface structure

Lighting, PITS

Loeb & Turner (2012)
– A search for artificially illuminated solar system objects using LSST.

Wright (2017)
– An examination of the possibility that the solar system could have been occupied in the remote past by a prior indigenous intelligence.

Atmospheres and Surfaces

Lin (2014)
– On the use of anthropogenic pollution as a novel biosignature for intelligent life in the planetary atmospheres.

Lingham & Loeb (2017)
– Artificial reflections from exoplanetary surfaces

Waste Heat / Dyson / Kardashev

Dyson (1960)
– The origin of the idea of Dyson Spheres.

Follow up letters to/from Dyson
– Dialogues on the topic of Dyson Spheres.

Kardashev (1964)
– The original classification of ETI civilizations based on energy consumption into Types I, II, and III.…..8..217K

The Byrds: CTA-120
– It’s successful METI! Also, SETI in pop culture: the forgotten false positive of CTA-102

Dyson spheres and Megastructures

Wright et al. (2014)
– The first paper in the Ĝ series, which motivated a search for KII and KIII civilizations based on waste heat.…792…26W

Carrigan (2009)
– A search for Dyson spheres using archival IRAS all-sky infrared survey data.

Annis (1999)
– An assessment of whether observed galaxies exhibit evidence of KIII civilizations based on their properties.

Arnold (2005)
– The presentation of the idea of transiting semaphores, megastructures in orbit whose aspect would be distinguishable by transit photometers.

Wright et al. (2016)
– The fourth installment in the Ĝ paper series and first mention of Tabby’s Star in a SETI context.

Badescu (1995)
– Thermodynamics of Dyson Spheres

Badescu & Cathcart (2000)
– “Stellar Engines”

Badescu & Cathcart (2006a)
– Dyson Spheres as “stellar engines”

Judson (2017)
– Energy trajectories of planetary life

Forgan (2013)
– Dyson spheres detected in transit

Bradbury (2001a)
– Limits of technology

Bradbury (2001b)
– Dyson sphere discussion

Jugaku, Noguchi, & Nishimura (1995)
– An early Dyson Sphere search

Jugaku & Nishimura (2004)
– Results of the early Dyson sphere search

Bursa (2017)
– A possible use for Solar-system scale engineering

“Nature Plus”

Davies (2010)
– Chapter from “The Eerie Silence”
– The idea is presented that sufficiently advanced technology is indistinguishable from nature, or “Nature Plus.”
– Under construction…

Villarroel et al. (2016)
– A search for disappearing stars.….152…76V

Research Portfolios and “Fringe” Ideas

Loeb (2008)
– Research Portfolios

Wright (2018)
– Jill Tarter Biography Review

Stevenson (2017)
– On Outré Ideas

Kuhn & Berdyugina (2015)
– SETI with a colossal telescope

SETI Synthesis

Bradbury (2011)
– “Dysonian” SETI
– MacDonald

Wright (2018)
– A call on the SETI community to adopt a comprehensive and definitive lexicon for the field.

Culture & Anthropology

Oman-Reagan (2017)
– The idea that in a first encounter with ETI, the differences between cultures and biology inhibit success.

Wright & Oman-Reagan (2017)
– On the public perception of SETI, the “giggle factor,” and the legacy of colonialism.

Dick (2006)
– Anthropology of SETI

Denning (2013)
– An anthropologist looks at SETI


Davies (2010)
– The Eerie Silence, Chapter 4: How Much Intelligence is Out There?
– Under construction…

Amazing Octopus
– An alien intelligence on Earth

Birds Using Fire
– Intelligent non-human use of fire

SETI in the Media

Andersen (2015)
– The first article on Tabby’s Star.

Late Night with Tyson
– Pop culture reaction to Tabby’s Star mania.

Grush (2015)
– A meta-article on the misrepresentation of scientific ideas in popular science articles.

Billings (2018)
– A look at the the reasoning behind scientific skepticism, especially when dealing with the ETI question.

Forgan (2016)
– A call to establish a post-detection protocol for SETI which reflects the modern pace of communication.

SETI protocols

IAA (2010)
– A formal document which outlines the protocols of conduct in a positive SETI detection scenario.

Gertz (2017)
– A fervent detestation of METI practices and its adherents.

Forgan (2018)
– A reformulation of the Rio scale.
– Under construction…