Carl Sagan: Difference between revisions - Wikipedia

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{{Short description|American astrophysicist, cosmologist and author (1934–1996)}}

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{{Infobox scientist

| name = Carl Sagan

| image = Carl Sagan Planetary Society cropped.png

| caption = Sagan in ~~the 1970s~~1980

| birth_name = Carl Edward Sagan

| birth_date = {{Birth date|1934|11|9}}

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* [[Klumpke-Roberts Award]] (1974)

* [[NASA Distinguished Public Service Medal]] (1977)

* [[Pulitzer Prize for General ~~Non-Fiction~~Nonfiction]] (1978)

* [[Oersted Medal]] (1990)

* [[Carl Sagan Award for Public Understanding of Science]] (1993)

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}}

'''Carl Edward Sagan''' ({{IPAc-en|ˈ|s|eɪ|ɡ|ən}}; {{respell|SAY|gən}}; November 9, 1934{{spaced ndash}}December 20, 1996) was an American [[astronomer]], [[planetary scientist]], and [[science communicator]]. His best known scientific contribution is his research on the possibility of [[extraterrestrial life]], including experimental demonstration of the production of [[amino acid]]s from basic chemicals by exposure to light. He assembled the first physical messages sent into space, the [[Pioneer plaque]] and the [[Voyager Golden Record]], which were universal messages that could potentially be understood by any [[Extraterrestrial life|extraterrestrial]] intelligence that might find them. He argued in favor of the hypothesis, which has since been accepted, that the high surface temperatures of [[Venus]] are the result of the [[greenhouse effect]].<ref name="surftemp">{{cite book |title=Conversations with Carl Sagan |edition=illustrated |first1=Carl |last1=Sagan |first2=Tom |last2=Head |publisher=University Press of Mississippi |year=2006 |isbn=978-1-57806-736-7 |page=[https://archive.org/details/conversationswit00saga/page/14 14] |url=https://archive.org/details/conversationswit00saga |url-access=registration}} [https://books.google.com/books?id=gJ1rDj2nR3EC&pg=PR14 Extract of page 14] {{Web archive |url=https://web.archive.org/web/20161203154130/https://books.google.com/books?id=gJ1rDj2nR3EC&pg=PR14 |date=December 3, 2016 }}</ref>

Initially an assistant professor at [[Harvard University|Harvard]], Sagan later moved to [[Cornell University]], where he spent most of his career. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books.<ref name="scholar"/> He wrote many [[popular science]] books, such as ''[[The Dragons of Eden]]'', ''[[Broca's Brain]]'', ''[[Pale Blue Dot (book)|Pale Blue Dot]]'' and ''[[The Demon-Haunted World]]''. He also co-wrote and narrated the award-winning 1980 television series ''[[Cosmos: A Personal Voyage]]'', which became the most widely watched series in the history of American [[public television]]: ''Cosmos'' has been seen by at least 500 million people in 60 countries.<ref name =Starchild>{{cite web |url=http://starchild.gsfc.nasa.gov/docs/StarChild/whos_who_level2/sagan.html |title=StarChild: Dr. Carl Sagan |work=StarChild |publisher=[[NASA]] |access-date=October 8, 2009 |archive-date=February 7, 2012 |archive-url=https://web.archive.org/web/20120207191139/http://starchild.gsfc.nasa.gov/docs/StarChild/whos_who_level2/sagan.html |url-status=live}}</ref> A book, also called ''[[Cosmos (Carl Sagan book)|Cosmos]]'', was published to accompany the series. Sagan also wrote a science-fiction novel, published in 1985, called ''[[Contact (novel)|Contact]]'', which became the basis for the 1997 film ''[[Contact (1997 American film)|Contact]]''. His papers, comprising 595,000 items,<ref>{{cite book |title=The Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archive: A Finding Aid to the Collection in the Library of Congress |date=2013 |publisher=Manuscript Division, Library of Congress |url=http://rs5.loc.gov/service/mss/eadxmlmss/eadpdfmss/2013/ms013113.pdf |access-date=January 17, 2016 |archive-date=March 8, 2016 |archive-url=https://web.archive.org/web/20160308005013/http://rs5.loc.gov/service/mss/eadxmlmss/eadpdfmss/2013/ms013113.pdf |url-status=live}}</ref> are archived in the [[Library of Congress]].<ref>{{cite web |last1=Lowensohn |first1=Josh |title=Massive Carl Sagan archive posted by Library of Congress |url=https://www.theverge.com/2014/2/4/5379446/massive-carl-sagan-archive-posted-by-library-of-congress |access-date=January 16, 2016 |website=The Verge |date=February 4, 2014 |archive-date=January 12, 2020 |archive-url=https://web.archive.org/web/20200112204114/https://www.theverge.com/2014/2/4/5379446/massive-carl-sagan-archive-posted-by-library-of-congress |url-status=live}}</ref>

Sagan was a popular public advocate of [[Scientific skepticism|skeptical scientific inquiry]] and the [[scientific method]]; he pioneered the field of [[exobiology]] and promoted the search for extraterrestrial intelligent life ([[Search for extraterrestrial intelligence|SETI]]). He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for [[Planetary science|Planetary Studies]]. Sagan and his works received numerous awards and honors, including the [[NASA Distinguished Public Service Medal]], the [[National Academy of Sciences]] [[Public Welfare Medal]], the [[Pulitzer Prize for General Non-Fiction]] (for his book ''The Dragons of Eden''), and (for ''Cosmos: A Personal Voyage''), two [[Emmy Award]]s, the [[Peabody Award]], and the [[Hugo Award]]. He married three times and had five children. After developing [[myelodysplastic syndrome|myelodysplasia]], Sagan died of [[pneumonia]] at the age of 62 on December 20, 1996.

== Early life==

===Childhood===

[[File:Carl Sagan in 1951 Allegarooter.jpg|thumb|upright|left|Sagan in [[Rahway High School]]'s 1951 yearbook]]

Carl Edward Sagan was born on November 9, 1934, in the [[Bensonhurst, Brooklyn|Bensonhurst]] neighborhood of New York City's [[Brooklyn]] borough ~~on November 9, 1934~~.<ref name=poundstone>[[#Poundstone|Poundstone 1999]], pp. 363–364, 374–375.</ref><ref name="nyt"/> His mother, Rachel Molly Gruber (1906–1982), was a housewife from New York City; his father, Samuel Sagan (1905–1979), was a Ukrainian-born garment worker who had emigrated from [[Kamianets-Podilskyi]] (then in the [[Russian Empire]]).<ref name="Internet Accuracy Project">{{cite web |title=Carl Sagan |url=http://www.accuracyproject.org/cbe-Sagan,Carl.html |website=Internet Accuracy Project |location=Grandville, MI |access-date=August 22, 2012 |archive-date=March 8, 2012 |archive-url=https://web.archive.org/web/20120308095615/http://www.accuracyproject.org/cbe-Sagan,Carl.html |url-status=live}}</ref> Sagan was named in honor of his maternal grandmother, Chaiya Clara, who had died while giving birth to her second child; she was, in Sagan's words, "the mother she [Rachel] never knew."<ref name="Davidson">[[#CITEREFDavidson1999|Davidson 1999]].</ref> Sagan's maternal grandfather later married a woman named Rose, who Sagan's sister, Carol, would later say, was "never accepted" as Rachel's mother because Rachel "knew she [Rose] wasn't her birth mother."<ref>{{Cite web |title=Carl Sagan |url=https://archive.nytimes.com/www.nytimes.com/books/first/d/davidson-sagan.html |access-date=May 7, 2021 |website=~~archive.nytimes.com~~The New York Times |archive-date=July 14, 2021 |archive-url=https://web.archive.org/web/20210714153902/https://archive.nytimes.com/www.nytimes.com/books/first/d/davidson-sagan.html |url-status=live}}</ref> Sagan's family lived in a modest apartment in Bensonhurst. He later described his family as [[Reform Judaism|Reform Jews]], the most [[Religious liberalism|liberal]] of Judaism's four main branches. He and his sister agreed that their father was not especially religious, but that their mother "definitely believed in God, and was active in the [[Synagogue|temple]] [...] and served only [[Kosher foods|kosher]] meat."{{Sfn|Davidson|1999|p=12}} During the worst years of the [[Great Depression|Depression]], his father worked as a movie theater usher.{{Sfn|Davidson|1999|p=12}}

According to biographer Keay Davidson, Sagan experienced a kind of "inner war" as a result of his close relationship with both his parents, who were in many ways "opposites." He traced his analytical inclinations to his mother, who had been extremely poor as a child in New York City during [[World War I]] and the 1920s,{{Sfn|Davidson|1999|p=2}} and whose later intellectual ambitions were sabotaged by her poverty, status as a woman and wife, and [[Jewish ethnicity]]. Davidson suggested she "worshipped her only son, Carl" because "he would fulfill her unfulfilled dreams."{{Sfn|Davidson|1999|p=2}} Sagan believed that he had inherited his sense of wonder from his father, who spent his free time giving apples to the poor or helping soothe tensions between workers and management within New York City's garment industry.{{Sfn|Davidson|1999|p=2}} Although awed by his son's intellectual abilities, Sagan's father also took his inquisitiveness in stride, viewing it as part of growing up.{{Sfn|Davidson|1999|p=2}} Later, during his career, Sagan would draw on his childhood memories to illustrate scientific points, as he did in his book ''[[Shadows of Forgotten Ancestors (book)|Shadows of Forgotten Ancestors]]''.{{Sfn|Davidson|1999|p=9}}

Describing his parents' influence on his later thinking, Sagan said: "My parents were not scientists. They knew almost nothing about science. But in introducing me simultaneously to skepticism and to wonder, they taught me the two uneasily cohabiting modes of thought that are central to the scientific method."<ref name="Spangenburg">[[#Spangenburg & Moser|Spangenburg & Moser 2004]], pp. 2–5.</ref> He recalled that a defining moment in his development came when his parents took him, at age four, to the [[1939 New York World's Fair]]. He later described his vivid memories of several exhibits there. One, titled ''[[Futurama (New York World's Fair)|America of Tomorrow]]'', included a moving map, which, as he recalled, "showed beautiful highways and [[Cloverleaf interchange|cloverleaves]] and little [[General Motors]] cars all carrying people to skyscrapers, buildings with lovely spires, flying buttresses—and it looked great!"{{Sfn|Davidson|1999|p=14}} Another involved a flashlight shining on a [[Solar cell|photoelectric cell]], which created a crackling sound, and another showed how the sound from a [[tuning fork]] became a wave on an [[oscilloscope]]. He also saw an exhibit of the then-nascent medium known as television. Remembering it, he later wrote: "Plainly, the world held wonders of a kind I had never guessed. How could a tone become a picture and light become a noise?"{{Sfn|Davidson|1999|p=14}}

Sagan also saw one of the fair's most publicized events: the burial at [[Flushing Meadows–Corona Park|Flushing Meadows]] of a [[time capsule]], which contained mementos from the 1930s to be recovered by Earth's descendants in a future millennium. Davidson wrote that this "thrilled Carl." As an adult, inspired by his memories of the World's Fair, Sagan and his colleagues would create similar time capsules to be sent out into the galaxy: the [[Pioneer plaque]] and the ''[[Voyager Golden Record]]'' précis.{{Sfn|Davidson|1999|p=15}}

During [[World War II]], Sagan's parents worried about the fate of their European relatives, but he was generally unaware of the details of the ongoing war. He wrote, "Sure, we had relatives who were caught up in the [[The Holocaust|Holocaust]]. [[Adolf Hitler|Hitler]] was not a popular fellow in our household... but on the other hand, I was fairly insulated from the horrors of the war." His sister, Carol, said that their mother "above all wanted to protect Carl... she had an extraordinarily difficult time dealing with World War II and the Holocaust."{{Sfn|Davidson|1999|p=15}} Sagan's book ''[[The Demon-Haunted World]]'' (1996) included his memories of this conflicted period, when his family dealt with the realities of the war in Europe, but tried to prevent it from undermining his optimistic spirit.<ref name="Spangenburg" />

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Soon after entering elementary school, Sagan began to express his strong inquisitiveness about nature. He recalled taking his first trips to the public library alone, at age five, when his mother got him a library card. He wanted to learn what stars were, since none of his friends or their parents could give him a clear answer: "I went to the librarian and asked for a book about stars [...] and the answer was stunning. It was that the Sun was a star, but really close. The stars were suns, but so far away they were just little points of light. The scale of the universe suddenly opened up to me. It was a kind of religious experience. There was a magnificence to it, a grandeur, a scale which has never left me. Never ever left me."{{Sfn|Davidson|1999|p=18}} When he was about six or seven, he and a close friend took trips to the [[American Museum of Natural History]], in [[Manhattan]]. While there, they visited the [[Hayden Planetarium]] and walked around exhibits of space objects, such as [[meteorite]]s, as well as displays of dinosaur skeletons and naturalistic scenes with animals. As Sagan later wrote, "I was transfixed by the dioramas—lifelike representations of animals and their habitats all over the world. Penguins on the dimly lit Antarctic ice [...] a family of gorillas, the male beating his chest [...] an American [[grizzly bear]] standing on his hind legs, ten or twelve feet tall, and staring me right in the eye."{{Sfn|Davidson|1999|p=18}}

Sagan's parents nurtured his growing interest in science, buying him chemistry sets and reading matter. But his fascination with outer space emerged as his primary focus, especially after he had read science fiction by such writers as [[H. G. Wells]] and [[Edgar Rice Burroughs]], stirring his curiosity about the possibility of life on [[Life on Mars|Mars]] and other ~~planet[[Life on Mars|s]]~~ planets.<ref name="sagan19780528" /> According to biographer Ray Spangenburg, Sagan's efforts in his early years to understand the mysteries of the planets became a "driving force in his life, a continual spark to his intellect, and a quest that would never be forgotten."<ref name="Spangenburg" /> In 1947, Sagan discovered the magazine ''[[Astounding Science Fiction]]'', which introduced him to more [[hard science fiction]] speculations than those in the Burroughs novels.<ref name="sagan19780528">{{Cite news |url=https://www.nytimes.com/1978/05/28/archives/growing-up-with.html |title=Growing up with Science Fiction |last=Sagan |first=Carl |date=May 28, 1978 |work=The New York Times |access-date=December 12, 2018 |page=SM7 |language=en-US |issn=0362-4331 |archive-date=December 11, 2018 |archive-url=https://web.archive.org/web/20181211180058/https://www.nytimes.com/1978/05/28/archives/growing-up-with.html |url-status=live}}</ref> That same year, [[mass hysteria]] developed about the possibility that extraterrestrial visitors had arrived in [[flying saucer]]s, and the young Sagan joined in the speculation that the flying "discs" people reported seeing in the sky might be alien spaceships.<ref name="anb.org">{{Cite encyclopedia |first=Keay |last=Davidson |title=Sagan, Carl (1934–1996), space scientist, author, science popularizer, TV personality, and antinuclear weapons activist |url=https://www.anb.org/view/10.1093/anb/9780198606697.001.0001/anb-9780198606697-e-1302612 |encyclopedia=American National Biography |publisher=Oxford University Press |~~date~~year=2000 |doi=10.1093/anb/9780198606697.article.1302612 |archive-url=https://web.archive.org/web/20210514010502/https://www.anb.org/view/10.1093/anb/9780198606697.001.0001/anb-9780198606697-e-1302612 |archive-date=May 14, 2021 |url-status=live |isbn=978-0-19-860669-7 |access-date=June 23, 2021}}</ref>

===Education===

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Before the end of high school, Sagan entered an essay writing contest in which he explored the idea that human contact with advanced life forms from another planet might be as disastrous for people on Earth as [[European colonization of the Americas|Native Americans' first contact with Europeans]] had been for Native Americans.<ref name="ReferenceA">[[#Poundstone|Poundstone 1999]], p. 15.</ref> The subject was considered controversial, but his rhetorical skill won over the judges and they awarded him first prize.<ref name="ReferenceA"/> When he was about to graduate from high school, his classmates voted him "most likely to succeed" and put him in line to be [[valedictorian]].<ref name="ReferenceA"/> He attended the [[University of Chicago]] because, despite his excellent high school grades, it was one of the very few colleges he had applied to that would consider accepting a 16-year-old. Its chancellor, [[Robert Maynard Hutchins]], had recently retooled the undergraduate [[College of the University of Chicago]] into an "ideal meritocracy" built on [[Great Books]], [[Socratic dialogue]], [[comprehensive examination]]s, and [[college early entrance program|early entrance to college]] with no age requirement.<ref name="ReferenceB">[[#Poundstone|Poundstone 1999]], p. 14.</ref>

As an honors-program [[Undergraduate education|undergraduate]], Sagan worked in the laboratory of geneticist [[Hermann Joseph Muller|H. J. Muller]] and wrote a thesis on the [[abiogenesis|origins of life]] with physical chemist [[Harold Urey]]. He also joined the Ryerson Astronomical Society.<ref>{{cite web |url=http://astro.uchicago.edu/RAS/ |title=Ryerson Astronomical Society |work=Ryerson Astronomical Society (RAS) |publisher=[[University of Chicago]] Department of Astronomy and Astrophysics |access-date=August 22, 2012 |archive-date=September 19, 2012 |archive-url=https://web.archive.org/web/20120919011234/http://astro.uchicago.edu/RAS/ |url-status=live}}</ref> In 1954, he was awarded a Bachelor of Arts with general and special honors<ref>[http://www.mit.edu/people/thb/SAGAN.pdf Carl Sagan] -– website of the [[Massachusetts Institute of Technology]]</ref> in what he quipped was "nothing."<ref>Sic. See {{cite book |title=Carl Sagan: A Biography |edition=illustrated |first1=Ray |last1=Spangenburg |first2=Kit |last2=Moser |first3=Diane |last3=Moser |publisher=Greenwood Publishing Group |year=2004 |isbn=978-0-313-32265-5 |page=28 |url=https://books.google.com/books?id=Z01FzDkprgUC |access-date=August 31, 2018 |archive-date=December 6, 2021 |archive-url=https://web.archive.org/web/20211206055120/https://books.google.com/books?id=Z01FzDkprgUC |url-status=live}} [https://books.google.com/books?id=Z01FzDkprgUC&pg=PA28 Extract of page 28] {{Webarchive |url=https://web.archive.org/web/20191225225756/https://books.google.com/books?id=Z01FzDkprgUC&pg=PA28 |date=December 25, 2019 }}</ref> In 1955, he earned a Bachelor of Science in physics. He went on to do graduate work at the University of Chicago, earning a Master of Science in physics in 1956 and a Doctor of Philosophy in astronomy and astrophysics in 1960. His doctoral thesis, submitted to the Department of Astronomy and Astrophysics, was entitled ''Physical Studies of the Planets''.<ref name=phd>{{cite thesis |last=Sagan |first=Carl |author-link=Carl Sagan |title=Physical Studies of the Planets |degree=PhD |year=1960 |publisher=University of Chicago |page=ii |quote=A thesis in four parts submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Astronomy, University of Chicago, June, 1960 |oclc=20678107 |id={{ProQuest|301918122}}}}</ref><ref>{{cite journal |date=November 11, 1993 |title=Graduate students receive first Sagan teaching awards |journal=University of Chicago Chronicle |volume=13 |issue=6 |access-date=August 30, 2013 |url=http://chronicle.uchicago.edu/931111/sagan.shtml |archive-date=March 10, 2012 |archive-url=https://web.archive.org/web/20120310091907/http://chronicle.uchicago.edu/931111/sagan.shtml |url-status=live}}</ref><ref>[[#Head|Head 2006]], p. xxi.</ref><ref>[[#Spangenburg & Moser|Spangenburg & Moser 2004]], p. 28.</ref> During his [[Postgraduate education|graduate studies]], he used the summer months to work with planetary scientist [[Gerard Kuiper]], who was his [[Doctoral advisor|dissertation director]],<ref name=mathgene>{{MathGenealogy|id=226265}}</ref> as well as physicist [[George Gamow]] and chemist [[Melvin Calvin]]. The title of Sagan's dissertation reflected interests he had in common with Kuiper, who had been president of the [[International Astronomical Union]]'s commission on "Physical Studies of Planets and Satellites" throughout the 1950s.<ref>{{Citation |last=Tatarewicz |first=Joseph N. |title=Space Technology & Planetary Astronomy |place=Bloomington, IN |publisher=Indiana University Press |series=Science, technology, and society |year=1990 |page=22 |isbn=978-0-253-35655-0}}</ref>

In 1958, Sagan and Kuiper worked on the classified military [[Project A119]], a secret [[U.S. Air Force]] plan to detonate a nuclear warhead on the Moon and document its effects.<ref>{{cite book |url=https://books.google.com/books?id=W1f4TvNUwLsC |title=Lunar Exploration: Human Pioneers and Robotic Surveyors |first=Paolo |last=Ulivi |date=April 6, 2004 |publisher=Springer Science & Business Media |isbn=978-1-85233-746-9 |access-date=April 15, 2016 |archive-date=January 1, 2014 |archive-url=https://web.archive.org/web/20140101183032/http://books.google.com/books?id=W1f4TvNUwLsC |url-status=live}}</ref> Sagan had a [[Top Secret]] clearance at the Air Force and a [[Classified information#Secret|Secret]] clearance with [[NASA]].<ref name="morrison">{{cite journal |last=Morrison |first=David |author-link=David Morrison (astrophysicist) |date=January–February 2007 |title=Carl Sagan's Life and Legacy as Scientist, Teacher, and Skeptic |url=http://www.csicop.org/si/show/carl_sagans_life_and_legacy_as_scientist_teacher_and_skeptic |journal=[[Skeptical Inquirer]] |volume=31 |issue=1 |pages=29–38 |issn=0194-6730 |access-date=August 31, 2013 |archive-url=https://web.archive.org/web/20160201115954/http://www.csicop.org/si/show/carl_sagans_life_and_legacy_as_scientist_teacher_and_skeptic |archive-date=February 1, 2016 |url-status=dead}}</ref> In 1999, an article published in the journal ''[[Nature (journal)|Nature]]'' revealed that Sagan had included the classified titles of two Project A119 papers in his 1959 application for a scholarship to [[University of California, Berkeley]]. A follow-up letter to the journal by project leader Leonard Reiffel confirmed Sagan's security leak.<ref>{{cite journal |last1=Reiffel |first1=Leonard |title=Sagan breached security by revealing US work on a lunar bomb project |journal=Nature |date=May 4, 2000 |volume=405 |issue=13 |page=Correspondence |doi=10.1038/35011148 |pmid=10811192 |doi-access=free | issn = 0028-0836}}</ref>

==Career and research ==

[[File:Who's Out There (1975).webm|thumb|250px|thumbtime=4:45|Sagan is one of those discussing the likelihood of [[extraterrestrial life|life on other planets]] in ''[[c:File:Who's Out There (1975).webm|Who's Out There?]]'' (1973), an [[CINE|award-winning]] [[NASA]] documentary film by [[Robert Drew]].<ref>{{cite web|url=https://drewassociates.com/films/whos-out-there|title=Who's Out There? -– Films -– Drew Associates|access-date=March 14, 2024|website=Drew Associates|archive-url=https://web.archive.org/web/20240314170516/https://drewassociates.com/films/whos-out-there/|archive-date=March 14, 2024}}</ref>]]

From 1960 to 1962 Sagan was a [[Miller Research Fellows|Miller Fellow]] at the [[University of California, Berkeley]].<ref>{{cite web |url=http://sciencereview.berkeley.edu/happy-belated-birthday-carl/ |title=Happy (Belated) Birthday Carl! |publisher=[[University of California, Berkeley]] The Berkeley Science Review |access-date=December 1, 2013 |date=November 11, 2013 |archive-date=December 3, 2013 |archive-url=https://web.archive.org/web/20131203045427/http://sciencereview.berkeley.edu/happy-belated-birthday-carl/ |url-status=dead}}</ref> Meanwhile, he published an article in 1961 in the journal ''Science'' on the atmosphere of Venus, while also working with [[NASA]]'s [[Mariner 2]] team, and served as a "Planetary Sciences Consultant" to the [[RAND Corporation]].{{Sfn|Davidson|1999|p=138}}

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{{quote box||align=left|width=25em|bgcolor = LightCyan|quote=Science is more than a body of knowledge; it is a way of thinking. I have a foreboding of an America in my children's or grandchildren's time – when the United States is a service and information economy; when nearly all the key manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what's true, we slide, almost without noticing, back into superstition and darkness... The dumbing down of America is most evident in the slow decay of substantive content in the enormously influential media, the 30 second sound bites (now down to 10 seconds or less), lowest common denominator programming, credulous presentations on pseudoscience and superstition, but especially a kind of celebration of ignorance.|source='''Carl Sagan''', from ''Demon-Haunted World'' (1995)<ref>Sagan, Carl. ''Demon-Haunted World: Science as a Candle in the Dark'' ([https://books.google.com/books?id=Yz8Y6KfXf9UC&q=foreboding%20of%20an%20America on Google Books], {{Web archive |url=https://web.archive.org/web/20221003060920/https://www.google.com/books/edition/The_Demon_Haunted_World/Yz8Y6KfXf9UC?gbpv=1&bsq=foreboding%20of%20an%20America |date=3 October 2022 }}), Ballantine Books (1996) p. 25.</ref>}}

Long before the ill-fated tenure process, Cornell University astronomer [[Thomas Gold]] had courted Sagan to move to [[Ithaca, New York]], and join the recently- hired astronomer [[Frank Drake]] ~~amongst~~among the faculty at Cornell. Following the denial of tenure from Harvard, Sagan accepted Gold's offer and remained a faculty member at Cornell for nearly 30 years until his death in 1996. Unlike Harvard, the smaller and more laid-back astronomy department at Cornell welcomed Sagan's growing celebrity status.{{Sfn|Davidson|1999|p=213}} Following two years as an associate professor, Sagan became a [[Professor|full professor]] at Cornell in 1970 and directed the Laboratory for [[Planetary science|Planetary Studies]] there. From 1972 to 1981, he was associate director of the Center for Radiophysics and Space Research (CRSR) at Cornell. In 1976, he became the David Duncan Professor of Astronomy and Space Sciences, a position he held for the remainder of his life.<ref>{{cite book |title=Conversations with Carl Sagan |edition=illustrated |first1=Carl |last1=Sagan |first2=Tom |last2=Head |publisher=Univ. Press of Mississippi |year=2006 |isbn=978-1-57806-736-7 |page=xxi |url=https://archive.org/details/conversationswit00saga |url-access=registration}} [https://books.google.com/books?id=gJ1rDj2nR3EC&pg=PR21 Extract of page xxi] {{Web archive |url=https://web.archive.org/web/20191223205906/https://books.google.com/books?id=gJ1rDj2nR3EC&pg=PR21 |date=December 23, 2019 }}.</ref>

Sagan was associated with the U.S. space program from its inception.{{Citation needed|date=November 2020}} From the 1950s onward, he worked as an advisor to [[NASA]], where one of his duties included briefing the [[Apollo program|Apollo]] [[astronaut]]s before their flights to the [[Moon]]. Sagan contributed to many of the [[robotic spacecraft]] missions that explored the [[Solar System]], arranging experiments on many of the expeditions. Sagan assembled the first physical message that was sent into space: a [[Gold plating|gold-plated]] [[Pioneer plaque|plaque]], attached to the space probe ''[[Pioneer 10]]'', launched in 1972. ''[[Pioneer 11]]'', also carrying another copy of the plaque, was launched the following year. He continued to refine his designs; the most elaborate message he helped to develop and assemble was the [[Voyager Golden Record]], which was sent out with the [[Voyager program|Voyager]] space probes in 1977. Sagan often challenged the decisions to fund the [[Space Shuttle]] and the [[International Space Station]] at the expense of further robotic missions.<ref name="CharlieRose">{{cite interview |last=Sagan |first=Carl |title=An Interview with Carl Sagan |url=https://www.youtube.com/watch?v=soF-aS169bw |work=[[Charlie Rose (TV series)|Charlie Rose]] |publisher=[[PBS]] |date=January 5, 1995 |access-date=August 30, 2013 |archive-date=July 14, 2015 |archive-url=https://web.archive.org/web/20150714182925/https://www.youtube.com/watch?v=soF-aS169bw |url-status=live}}</ref>

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He is also the 1994 recipient of the [[Public Welfare Medal]], the highest award of the [[National Academy of Sciences]] for "distinguished contributions in the application of science to the public welfare."<ref>{{cite web |title=Carl Sagan |url=http://www.planetary.org/about/our-founders/carl-sagan.html |publisher=[[The Planetary Society]] |location=Pasadena, CA |access-date=August 30, 2013 |archive-date=February 21, 2015 |archive-url=https://web.archive.org/web/20150221051400/http://www.planetary.org/about/our-founders/carl-sagan.html |url-status=live}}</ref> He was denied membership in the academy, reportedly because his media activities made him unpopular with many other scientists.<ref>{{cite journal |last=Benford |first=Gregory |author-link=Gregory Benford |year=1997 |title=A Tribute to Carl Sagan: Popular & Pilloried |journal=[[Skeptic (U.S. magazine)|Skeptic]] |volume=13 |issue=1 |url=http://www.skeptic.com/reading_room/popular-and-pilloried/ |access-date=February 18, 2011 |archive-date=April 16, 2011 |archive-url=https://web.archive.org/web/20110416091611/http://www.skeptic.com/reading_room/popular-and-pilloried/ |url-status=live}}</ref><ref>{{cite web |url=http://www.michaelshermer.com/2003/11/candle-in-the-dark/ |title=Candle in the Dark |last=Shermer |first=Michael |author-link=Michael Shermer |website=The Works of Michael Shermer |publisher=Michael Shermer |access-date=March 10, 2013 |date=November 2, 2003 |archive-date=September 27, 2009 |archive-url=https://web.archive.org/web/20090927101121/http://www.michaelshermer.com/2003/11/candle-in-the-dark/ |url-status=live}} Article originally published in November 2003 issue of ''[[Scientific American]]''.</ref><ref>{{cite journal |last=Impey |first=Chris |author-link=Chris Impey |date=January–February 2000 |title=Carl Sagan, Carl Sagan: Biographies Echo an Extraordinary Life |journal=[[American Scientist]] |volume=88 |issue=1 |type=Book review |issn=0003-0996 |access-date=March 10, 2013 |url=http://www.americanscientist.org/bookshelf/pub/carl-sagan-carl-sagan-biographies-echo-an-extraordinary-life |archive-date=May 16, 2013 |archive-url=https://web.archive.org/web/20130516121457/http://www.americanscientist.org/bookshelf/pub/carl-sagan-carl-sagan-biographies-echo-an-extraordinary-life |url-status=live}}</ref>

{{as of|2017}}, Sagan is the most cited SETI scientist and one of the most cited planetary scientists.<ref name="scholar">{{Cite web |url=https://scholar.google.com/citations?user=Wd1k3voAAAAJ |title=Carl Sagan |~~website~~publisher=~~scholar.google.com~~Google Scholar |access-date=November 20, 2018 |archive-date=December 23, 2019 |archive-url=https://web.archive.org/web/20191223173449/https://scholar.google.com/citations?user=Wd1k3voAAAAJ |url-status=live}}</ref>

===''Cosmos'': popularizing science on TV===

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After ''Cosmos'' aired, Sagan became associated with the [[catchphrase]] "billions and billions", although he never actually used the phrase in the ''Cosmos'' series.<ref name="BandB">[[#Sagan & Druyan 1997|Sagan & Druyan 1997]], pp. 3–4.</ref> He rather used the term "billions ''upon'' billions."<ref>{{cite book |editor-last=Shapiro |editor-first=Fred R. |editor-link=Fred R. Shapiro |others=Foreword by [[Joseph Epstein (writer)|Joseph Epstein]] |title=The Yale Book of Quotations |year=2006 |publisher=[[Yale University Press]] |location=New Haven, CT |isbn=978-0-300-10798-2 |oclc=66527213 |lccn=2006012317 |page=[https://archive.org/details/isbn_9780300107982/page/660 660] |url=https://archive.org/details/isbn_9780300107982/page/660}}</ref>

[[Richard Feynman]], a precursor to Sagan, used the phrase "billions and billions" many times in his "[[The Feynman Lectures on Physics|red books]]." However, Sagan's frequent use of the word ''billions'' and distinctive delivery emphasizing the "b" (which he did intentionally, in place of more cumbersome alternatives such as "billions with a 'b{{'"}}, in order to distinguish the word from "millions")<ref name="BandB" /> made him a favorite target of comic performers, including [[Johnny Carson]],<ref>{{cite journal |editor-last=Frazier |editor-first=Kendrick |editor-link=Kendrick Frazier |date=July–August 2005 |title=Carl Sagan Takes Questions: More From His 'Wonder and Skepticism' CSICOP 1994 Keynote |journal=Skeptical Inquirer |volume=29 |issue=4 |url=http://www.csicop.org/si/show/carl_sagan_takes_questions |access-date=March 25, 2010 |archive-url=https://web.archive.org/web/20161221054208/http://www.csicop.org/si/show/carl_sagan_takes_questions |archive-date=December 21, 2016 |url-status=dead}}</ref><ref>{{cite web |url=https://www.youtube.com/watch?v=iIbbTHQmPkE |archive-url=https://web.archive.org/web/20161023205508/https://www.youtube.com/watch?v=iIbbTHQmPkE |archive-date=October 23, 2016 |url-status=live |title=Carl Sagan (Cosmos) Parody by Johnny Carson (1980) |author=24fpsfan |date=December 22, 2012 |via=YouTube |access-date=November 4, 2016}}</ref> [[Gary Kroeger]], [[Mike Myers]], [[Bronson Pinchot]], [[Penn Jillette]], [[Harry Shearer]], and others. [[Frank Zappa]] satirized the line in the song "Be in My Video", noting as well "atomic light." Sagan took this all in good humor, and his final book was ~~entitled~~titled ''[[Billions and Billions]]'', which opened with a tongue-in-cheek discussion of this catchphrase, observing that Carson was an amateur astronomer and that Carson's comic caricature often included real science.<ref name="BandB" />

As a humorous tribute to Sagan and his association with the catchphrase "billions and billions", a {{anchor |Sagan units}}''[[wikt:Sagan#Noun|sagan]]'' has been defined as a [[List of humorous units of measurement|unit of measurement]] equivalent to a very large number of anything.<ref>{{cite news |title=Footprints on the Infobahn |first=William |last=Safire |author-link=William Safire |url=https://www.nytimes.com/1994/04/17/magazine/on-language-footprints-on-the-infobahn.html |newspaper=The New York Times |date=April 17, 1994 |access-date=August 31, 2013 |archive-date=November 13, 2013 |archive-url=https://web.archive.org/web/20131113054310/http://www.nytimes.com/1994/04/17/magazine/on-language-footprints-on-the-infobahn.html |url-status=live}}</ref><ref name="annbot">{{cite journal |last=Gresshoff |first=P. M. |year=2004 |title=Scheel D. and Wasternack C.(eds) Plant Signal Transduction |journal=[[Annals of Botany]] |volume=93 |issue=6 |pages=783–784 |type=Book review ~~|url=~~ |doi=10.1093/aob/mch102 |pmc=4242307}}</ref>

===Sagan's number===

Sagan's number is the number of [[star]]s in the [[observable universe]].<ref>{{cite web |url=http://www.numericana.com/answer/sagan.htm |title=Sizing up the Universe - Stars, Sand and Nucleons - Numericana |first=Gerard |last=Michon |website=~~www.~~numericana.com |access-date=April 1, 2018 |archive-date=April 11, 2020 |archive-url=https://web.archive.org/web/20200411012359/http://www.numericana.com/answer/sagan.htm |url-status=live}}</ref> This number is reasonably well defined, because it is known what stars are and what the observable universe is, but its value is highly uncertain.

* In 1980, Sagan estimated it to be 10 [[sextillion]] in [[short scale]] (1022).<ref>{{cite book |last=Sagan |first=Carl |title=Cosmos |year=1985 |page=[https://archive.org/details/cosmoscosm00saga/page/3 3] |publisher=Balantine Books |isbn=0345331354 |url-access=registration |url=https://archive.org/details/cosmoscosm00saga/page/3}}</ref>

* In 2003, it was estimated to be 70 sextillion (7 × 1022).<ref>{{cite web |work=CNN Science |url=http://edition.cnn.com/2003/TECH/space/07/22/stars.survey/ |title=Star survey reaches 70 sextillion: And that's only the stars we can actually see |date=July 23, 2003 |location=Sydney, Australia |access-date=October 27, 2014 |archive-date=August 5, 2003 |archive-url=https://web.archive.org/web/20030805032320/http://edition.cnn.com/2003/TECH/space/07/22/stars.survey/ |url-status=live}}</ref><ref>{{cite web |publisher=Australian National University Media Releases |url=http://info.anu.edu.au/ovc/Media/Media_Releases/2003/030717StarCount/ |title=STAR COUNT: ANU ASTRONOMER MAKES BEST YET |date=July 17, 2003 |location=Sydney, Australia |access-date=October 27, 2015 |archive-url=https://web.archive.org/web/20110309114938/http://info.anu.edu.au/ovc/Media/Media_Releases/2003/030717StarCount |archive-date=March 9, 2011}}</ref>

* In 2010, it was estimated to be 300 sextillion (3 × 1023).<ref>{{cite web |work=[[~~Huffington Post~~HuffPost]] |url=https://www.huffingtonpost.com/2010/12/01/number-of-stars-in-universe_n_790563.html |title=Number Of Stars In The Universe Could Be 300 Sextillion, Triple The Amount Scientists Previously Thought: Study |date=December 1, 2010 |access-date=September 3, 2016 |archive-url=https://web.archive.org/web/20101204134457/http://www.huffingtonpost.com/2010/12/01/number-of-stars-in-universe_n_790563.html |archive-date=December 4, 2010 |url-status=dead}}</ref>

=== Scientific and critical thinking advocacy ===

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[[File:Planetary society2.jpg|thumb|left|[[The Planetary Society]] members at the organization's founding. Sagan is seated on the right.]]

At the height of the [[Cold War]], Sagan became involved in [[nuclear disarmament]] efforts by promoting hypotheses on the effects of [[nuclear warfare|nuclear war]], when [[Paul Crutzen]]'s [[Nuclear winter#1982|"Twilight at Noon"]] concept suggested that a substantial nuclear exchange could trigger a [[Nuclear winter#1982|nuclear twilight]] and upset the delicate balance of life on Earth by cooling the surface. In 1983 he was one of five authors—the "S"—in the follow-up [[Nuclear winter#1983|"TTAPS"]] model (as the research article came to be known), which contained the first use of the term "[[nuclear winter]]", which his colleague [[Richard P. Turco]] had coined.<ref>{{cite journal |last1=Turco |first1=R. P. |author-link1=Richard P. Turco |last2=Toon |first2=O. B. |author-link2=Owen Toon |last3=Ackerman |first3=T. P. |last4=Pollack |first4=J. B. |last5=Sagan |first5=C. |date=January 12, 1990 |title=Climate and smoke: an appraisal of nuclear winter |journal=[[Science (journal)|Science]] |volume=247 |issue=4939 |pages=166–176 |doi=10.1126/science.11538069 |pmid=11538069 |bibcode=1990Sci...247..166T |citeseerx=10.1.1.584.8478}} [https://www.jstor.org/stable/2873486 JSTOR] {{Webarchive |url=https://web.archive.org/web/20180917222355/https://www.jstor.org/stable/2873486 |date=September 17, 2018 }} link to full text article. Carl Sagan discussed his involvement in the political nuclear winter debates and his erroneous global cooling prediction for the Gulf War fires in his book ''[[The Demon-Haunted World]]''.</ref> In 1984 he co-authored the book ''[[The Cold and the Dark: The World after Nuclear War]]'' and in 1990 the book ''A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race'', which explains the nuclear-winter hypothesis and advocates [[nuclear disarmament]]. Sagan received a great deal of skepticism and disdain for the use of media to disseminate a very uncertain hypothesis. A personal correspondence with nuclear physicist [[Edward Teller]] around 1983 began amicably, with Teller expressing support for continued research to ascertain the credibility of the winter hypothesis. However, Sagan and Teller's correspondence would ultimately result in Teller writing: "A propagandist is one who uses incomplete information to produce maximum persuasion. I can compliment you on being, indeed, an excellent propagandist, remembering that a propagandist is the better the less he appears to be one."<ref name="rubinsonp66913">{{cite web |url=https://www.lib.utexas.edu/etd/d/2008/rubinsonp66913/rubinsonp66913.pdf |title=The U.S. National Security State and Scientists'Challenge to Nuclear Weapons during the Cold War. Paul Harold Rubinson 2008 |url-status=dead |archive-url=https://web.archive.org/web/20140924041711/https://www.lib.utexas.edu/etd/d/2008/rubinsonp66913/rubinsonp66913.pdf |archive-date=September 24, 2014}}</ref> Biographers of Sagan would also comment that from a scientific viewpoint, nuclear winter was a low point for Sagan, although, politically speaking, it popularized his image ~~amongst~~among the public.<ref name="rubinsonp66913"/>

The adult Sagan remained a fan of science fiction, although disliking stories that were not realistic (such as ignoring the [[inverse-square law]]) or, he said, did not include "thoughtful pursuit of alternative futures."{{r|sagan19780528}} He wrote books to popularize science, such as ''Cosmos'', which reflected and expanded upon some of the themes of ''A Personal Voyage'' and became the best-selling science book ever published in English;<ref>{{cite web |url=http://science.discovery.com/convergence/cosmos/bio/bio.html?clik=fsmain_feat3 |title=Meet Carl Sagan |work=[[Science (TV network)|The Science Channel]] |publisher=[[Discovery Communications]] |archive-url=https://web.archive.org/web/20070518042909/http://science.discovery.com/convergence/cosmos/bio/bio.html?clik=fsmain_feat3 |archive-date=May 18, 2007 |access-date=August 31, 2013}}</ref> ''[[The Dragons of Eden]]: Speculations on the Evolution of Human Intelligence'', which won a [[Pulitzer Prize]]; and ''[[Broca's Brain (book)|Broca's Brain: Reflections on the Romance of Science]]''. Sagan also wrote the best-selling science fiction novel ''[[Contact (novel)|Contact]]'' in 1985, based on a [[film treatment]] he wrote with his wife, Ann Druyan, in 1979, but he did not live to see the book's 1997 [[Contact (1997 American film)|motion-picture adaptation]], which starred [[Jodie Foster]] and won the 1998 [[Hugo Award]] for Best Dramatic Presentation.

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Sagan wrote a sequel to ''Cosmos'', ''[[Pale Blue Dot (book)|Pale Blue Dot: A Vision of the Human Future in Space]]'', which was selected as a notable book of 1995 by ''[[The New York Times]]''. He appeared on PBS's ''[[Charlie Rose (TV series)|Charlie Rose]]'' program in January 1995.<ref name="CharlieRose" /> Sagan also wrote the introduction for [[Stephen Hawking]]'s bestseller ''[[A Brief History of Time]]''. Sagan was also known for his popularization of science, his efforts to increase scientific understanding among the general public, and his positions in favor of [[scientific skepticism]] and against [[pseudoscience]], such as his [[Debunker|debunking]] of the [[Betty and Barney Hill abduction]]. To mark the tenth anniversary of Sagan's death, [[David Morrison (astrophysicist)|David Morrison]], a former student of Sagan, recalled "Sagan's immense contributions to planetary research, the public understanding of science, and the skeptical movement" in ''[[Skeptical Inquirer]]''.<ref name="morrison" />

Following [[Saddam Hussein]]'s threats to light [[Kuwait]]'s oil wells on fire in response to any physical challenge to Iraqi control of the oil assets, Sagan together with his "TTAPS" colleagues and [[Paul Crutzen]], warned in January 1991 in ''[[The Baltimore Sun]]'' and ''[[Wilmington Morning Star]]'' newspapers that if the fires were left to burn over a period of several months, enough smoke from the 600 or so 1991 [[Kuwaiti oil fires]] "might get so high as to disrupt agriculture in much of South Asia ..." and that this possibility should "affect the war plans";<ref>{{Cite web |url=http://articles.baltimoresun.com/1991-01-23/news/1991023131_1_kuwait-saddam-hussein-sagan |title=Baltimore Sun – We are currently unavailable in your region |date=January 23, 1991 |access-date=October 3, 2014 |archive-date=October 6, 2014 |archive-url=https://web.archive.org/web/20141006144456/http://articles.baltimoresun.com/1991-01-23/news/1991023131_1_kuwait-saddam-hussein-sagan |url-status=live}}</ref><ref>[https://news.google.com/newspapers?id=6tEVAAAAIBAJ&sjid=RBQEAAAAIBAJ&pg=6851,2148654 ''Wilmington morning Star''] {{Webarchive |url=https://web.archive.org/web/20220605142615/https://news.google.com/newspapers?id=6tEVAAAAIBAJ&sjid=RBQEAAAAIBAJ&pg=6851,2148654 |date=June 5, 2022 }}. January 21, 1991.</ref> these claims were also the subject of a televised debate between Sagan and physicist [[Fred Singer]] on January 22, aired on the [[ABC News (United States)|ABC News]] program ''[[Nightline (US news program)|Nightline]]''.<ref>{{cite web |url=https://www.scribd.com/doc/4960296/The-Kuwaiti-Oli-Fires |title=The Kuwaiti Oil Fires |author=Hirschmann, Kris |publisher=Facts on File |url-status=dead |archive-url=https://web.archive.org/web/20140102193647/http://www.scribd.com/doc/4960296/The-Kuwaiti-Oli-Fires |archive-date=January 2, 2014}}</ref><ref>{{cite episode |title=FIRST ISRAELI SCUD FATALITIES OIL FIRES IN KUWAIT |series=Nightline |series-link=Nightline (US news program) |network=ABC |air-date=January 22, 1991 |transcript=yes}}</ref>[[File:F-14A VF-114 over burning Kuwaiti oil well 1991.JPEG|thumb|left|Sagan admitted that he had overestimated the danger posed by the 1991 [[Kuwaiti oil fires]].]] In the televised debate, Sagan argued that the effects of the smoke would be similar to the effects of a [[nuclear winter]], with Singer arguing to the contrary. After the debate, the fires burnt for many months before extinguishing efforts were complete. The results of the smoke did not produce continental-sized cooling. Sagan later conceded in ''The Demon-Haunted World'' that the prediction did not turn out to be correct: "it ''was'' pitch black at noon and temperatures dropped 4–6 °C over the [[Persian Gulf]], but not much smoke reached stratospheric altitudes and Asia was spared."<ref>[[#Sagan 1995|Sagan 1995]], p. 257.</ref>

In his later years, Sagan advocated the creation of an organized search for asteroids/[[near-Earth object]]s (NEOs) that might impact the Earth but to forestall or postpone developing the technological methods that would be needed to defend against them.<ref>[[#Head|Head 2006]], p. 86–87.</ref> He argued that all of the numerous methods proposed to [[asteroid impact avoidance|alter the orbit of an asteroid]], including the employment of [[nuclear weapon design|nuclear detonations]], created a [[Asteroid impact avoidance#Deflection technology concerns|deflection dilemma]]: if the ability to deflect an asteroid away from the Earth exists, then one would also have the ability to divert a non-threatening object towards Earth, creating an immensely destructive weapon.<ref name="auto">{{Cite journal |last1=Sagan |first1=Carl |last2=Ostro |first2=Steven J. |author-link2=Steven J. Ostro |date=Summer 1994 |title=Long-Range Consequences Of Interplanetary Collisions |journal=[[Issues in Science and Technology]] |volume=10 |issue=4 |pages=67–72 |issn=0748-5492 |bibcode=1994IST....10...67S |access-date=August 31, 2013 |url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/33108/1/94-1042.pdf |url-status=dead |archive-url=https://web.archive.org/web/20131203014812/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/33108/1/94-1042.pdf |archive-date=December 3, 2013}}</ref><ref name="e-reading.club">{{cite web |url=http://www.e-reading.club/chapter.php/72440/26/Sagan_-_Pale_Blue_Dot__A_Vision_of_the_Human_Future_in_Space.html |title=Chapter 18. The Marsh of Camarina – Pale Blue Dot: A Vision of the Human Future in Space |work=e-reading.club |access-date=September 1, 2015 |archive-date=September 24, 2015 |archive-url=https://web.archive.org/web/20150924003823/http://www.e-reading.club/chapter.php/72440/26/Sagan_-_Pale_Blue_Dot__A_Vision_of_the_Human_Future_in_Space.html |url-status=live}}</ref> In a 1994 paper he co-authored, he ridiculed a 3three-day -long "[[Asteroid impact avoidance#Nuclear explosive device|Near-Earth Object Interception Workshop]]" held by [[Los Alamos National Laboratory]] (LANL) in 1993 that did not, "even in passing" state that such interception and deflection technologies could have these "ancillary dangers."<ref name="auto"/>

Sagan remained hopeful that the natural NEO impact threat and the intrinsically double-edged essence of the methods to prevent these threats would serve as a "new and potent motivation to maturing international relations."<ref name="auto"/><ref>{{cite podcast |url=http://www.astrosociety.org/silicon-valley-astronomy-lectures/taking-a-hit-asteroid-impacts-and-evolution/ |title=Taking a Hit: Asteroid Impacts & Evolution |website=Astronomical Society of the Pacific |publisher=[[Astronomical Society of the Pacific]] |last=Morrison |first=David |author-link=David Morrison (astrophysicist) |date=October 3, 2007 |access-date=August 31, 2013 |archive-date=August 18, 2014 |archive-url=https://web.archive.org/web/20140818231737/http://www.astrosociety.org/silicon-valley-astronomy-lectures/taking-a-hit-asteroid-impacts-and-evolution/ |url-status=dead}}</ref> Later acknowledging that, with sufficient international oversight, in the future a "work our way up" approach to implementing nuclear explosive deflection methods could be fielded, and when sufficient knowledge was gained, to use them to aid in [[mining asteroids]].<ref name="e-reading.club"/> His interest in the use of nuclear detonations in space grew out of his work in 1958 for the [[Armour Research Foundation]]'s [[Project A119]], concerning the possibility of detonating a nuclear device on the lunar surface.<ref>{{cite web |url=https://medium.com/war-is-boring/3516ac20ae1e |title=When Earth Dreamed of Nuking the Moon |last1=Gault |first1=Matthew |date=November 28, 2013 |website=medium.com |publisher=War is Boring |access-date=November 28, 2013 |archive-date=December 3, 2013 |archive-url=https://web.archive.org/web/20131203014738/https://medium.com/war-is-boring/3516ac20ae1e |url-status=live}}</ref>

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{{blockquote|Wherever you turned, there was one astronomer being quoted on everything, one astronomer whose face you were seeing on TV, and one astronomer whose books had the preferred display slot at the local bookstore.}}

Some, like Urey, later ~~came to realize~~believed that Sagan's popular brand of scientific advocacy was beneficial to the science as a whole.{{Sfn|Davidson|1999|p=297}} Urey especially liked Sagan's 1977 book ''[[The Dragons of Eden]]'' and wrote Sagan with his opinion: "I like it very much and am amazed that someone like you has such an intimate knowledge of the various features of the problem... I congratulate you... You are a man of many talents."{{Sfn|Davidson|1999|p=297}}

Sagan was accused of borrowing some ideas of others for his own benefit and countered these claims by explaining that the misappropriation was an unfortunate side effect of his role as a science communicator and explainer, and that he attempted to give proper credit whenever possible.{{Sfn|Davidson|1999|p=203}}

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Sagan believed that the [[Drake equation]], on substitution of reasonable estimates, suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations highlighted by the [[Fermi paradox]] suggests [[Technology|technological]] civilizations tend to self-destruct. This stimulated his interest in identifying and publicizing ways that humanity could destroy itself, with the hope of avoiding such a [[Risks to civilization, humans, and planet Earth|cataclysm]] and eventually becoming a [[spacefaring]] species. Sagan's deep concern regarding the potential destruction of [[Risks to civilization, humans, and planet Earth|human civilization]] in a [[nuclear holocaust]] was conveyed in a memorable cinematic sequence in the final episode of ''Cosmos'', called "Who Speaks for Earth?" Sagan had already resigned{{date?}} from the [[United States Air Force Scientific Advisory Board|Air Force Scientific Advisory Board]]'s UFO-investigating [[Condon Committee]] and voluntarily surrendered his [[Security clearance#Top Secret|top-secret clearance]] in protest over the [[Vietnam War]].<ref>{{cite journal |last=Druyan |first=Ann |author-link=Ann Druyan |date=November 2000 |title=A New Sense of the Sacred Carl Sagan's 'Cosmic Connection' |journal=[[American Humanist Association|The Humanist]] |volume=60 |issue=6 |access-date=December 20, 2023 |url=https://www.thefreelibrary.com/A+New+Sense+of+the+Sacred+Carl+Sagan%27s+%22Cosmic+Connection%22.-a078889720 |archive-date=October 3, 2022 |archive-url=https://web.archive.org/web/20221003060924/https://www.gale.com/databases/questia |url-status=live}}</ref> Following his marriage to his third wife (novelist Ann Druyan) in June 1981, Sagan became more politically active—particularly in opposing escalation of the [[nuclear arms race]] under President [[Ronald Reagan]].

[[File:US and USSR nuclear stockpiles.svg|thumb|The United States and [[Soviet Union]]/Russia nuclear stockpiles, in [[Historical nuclear weapons stockpiles and nuclear tests by country|total number of nuclear bombs/warheads in existence]] throughout the [[Cold War]] and post-Cold War era]]

In March 1983, Reagan announced the [[Strategic Defense Initiative]]—a multibillion-dollar project to develop a comprehensive [[missile defense|defense]] against attack by [[Nuclear weapons delivery#Ballistic missile|nuclear missiles]], which was quickly dubbed the "Star Wars" program. Sagan spoke out against the project, arguing that it was technically impossible to develop a system with the level of perfection required, and far more expensive to build such a system than it would be for an enemy to defeat it through [[Decoy#Military decoy|decoys]] and other means—and that its construction would seriously destabilize the "nuclear balance" between the United States and the [[Soviet Union]], making further progress toward [[nuclear disarmament]] impossible.<ref>{{cite web |url=https://www.youtube.com/watch?v=fVUk30GFsL4 |archive-url=https://web.archive.org/web/20150711151236/https://www.youtube.com/watch?v=fVUk30GFsL4 |archive-date=July 11, 2015 |url-status=dead |title=YouTube |~~website~~via=YouTube}}</ref>

When Soviet leader [[Mikhail Gorbachev]] declared a unilateral moratorium on the [[Nuclear weapons testing|testing of nuclear weapons]], which would begin on August 6, 1985—the 40th anniversary of the [[Nuclear weapon#Fission weapons|atomic bombing]] of [[Atomic bombings of Hiroshima and Nagasaki|Hiroshima]]—the Reagan administration dismissed the dramatic move as nothing more than propaganda and refused to follow suit. In response, US [[Anti-nuclear movement|anti-nuclear]] and peace activists staged a series of protest actions at the [[Nevada National Security Site|Nevada Test Site]], beginning on Easter Sunday in 1986 and continuing through 1987. Hundreds of people in the "[[Nevada Desert Experience]]" group were arrested, including Sagan, who was arrested on two separate occasions as he climbed over a chain-link fence at the test site during the underground [[Operation Charioteer]] and [[Operation Musketeer (Nuclear test)|United States's Musketeer nuclear test series]] of detonations.<ref>[[#Spangenburg & Moser|Spangenburg & Moser 2004]], p. 106.</ref>

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Sagan was also a vocal advocate of the controversial notion of [[testosterone poisoning]], arguing in 1992 that human males could become gripped by an "unusually severe [case of] testosterone poisoning" and this could compel them to become [[genocidal]].<ref>{{cite book |title=Rethinking Risk and the Precautionary Principle |first1=Julian |last1=Morris |publisher=Butterworth-Heinemann |year=2000 |isbn=978-0-08-051623-3 |page=116 |url=https://books.google.com/books?id=XX6Us6SjLYkC}} [https://books.google.com/books?id=XX6Us6SjLYkC&pg=PA116 Extract of page 116] {{Webarchive |url=https://web.archive.org/web/20191220111727/https://books.google.com/books?id=XX6Us6SjLYkC&pg=PA116 |date=December 20, 2019 }}.</ref> In his review of [[Moondance magazine]] writer [[Daniela Gioseffi]]'s 1990 book ''Women on War'', he argues that females are the only half of humanity "untainted by testosterone poisoning."<ref>[http://www.italianamericanwriters.com/womenonwar.html Women On War] {{Webarchive |url=https://web.archive.org/web/20141006123300/http://www.italianamericanwriters.com/womenonwar.html |date=October 6, 2014 }}, Daniela Gioseffi.</ref> One chapter of his 1993 book ''[[Shadows of Forgotten Ancestors (book)|Shadows of Forgotten Ancestors]]'' is dedicated to testosterone and its alleged poisonous effects.<ref>{{cite book |title=Atheists in America |edition=reprinted |first1=Melanie E. |last1=Brewster |publisher=Columbia University Press |year=2014 |isbn=978-0-231-53700-1 |page=102 |url=https://books.google.com/books?id=iMjaAgAAQBAJ |access-date=February 28, 2016 |archive-date=December 23, 2019 |archive-url=https://web.archive.org/web/20191223201256/https://books.google.com/books?id=iMjaAgAAQBAJ |url-status=live}} [https://books.google.com/books?id=iMjaAgAAQBAJ&pg=PA102 Extract of page 102] {{Webarchive |url=https://web.archive.org/web/20191221205142/https://books.google.com/books?id=iMjaAgAAQBAJ&pg=PA102 |date=December 21, 2019 }}.</ref>

In 1989, Carl Sagan was interviewed by [[Ted Turner]] whether he believed in socialism and responded that: "I'm not sure what a socialist is. But I believe the government has a responsibility to care for the people... I'm talking about making the people self-reliant."<ref>{{Cite web |url=https://www.youtube.com/watch?v=rDK2chgNPZM |archive-url=https://ghostarchive.org/varchive/youtube/20211124/rDK2chgNPZM |archive-date=November 24, 2021 |url-status=live |title=Ted Turner asks Carl Sagan if he is a socialist. |date=March 14, 2016 |via=~~www.youtube.com~~YouTube}}{{cbignore}}</ref>

== Personal life and beliefs ==

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In 1994, engineers at [[Apple Inc.|Apple Computer]] code-named the [[Power Macintosh 7100]] "Carl Sagan" in the hope that Apple would make "billions and billions" with the sale of the PowerMac 7100.<ref name=poundstone /> The name was only used internally, but Sagan was concerned that it would become a product endorsement and sent Apple a cease-and-desist letter. Apple complied, but engineers retaliated by changing the internal codename to "BHA" for "[[Notable litigation of Apple Computer#Libel dispute with Carl Sagan|Butt-Head Astronomer]]."<ref name="Poundstone, p. 364">[[#Poundstone|Poundstone 1999]], p. 364</ref><ref name="Linzmayer">{{cite news |title=This Week in Apple History: November 14–20: McIntosh, IIe Killed, Butt-Head Astronomer |first1=Owen |last1=Linzmayer |first2=Bryan |last2=Chaffin |url=http://www.macobserver.com/columns/thisweek/2004/20041120.shtml |work=The Mac Observer |publisher=The Mac Observer, Inc. |date=November 15, 2004 |access-date=July 23, 2012 |archive-date=February 19, 2012 |archive-url=https://web.archive.org/web/20120219170529/http://www.macobserver.com/columns/thisweek/2004/20041120.shtml |url-status=live}}</ref> In November 1995, after further legal battle, an out-of-court settlement was reached and Apple's office of trademarks and patents released a conciliatory statement that "Apple has always had great respect for Dr. Sagan. It was never Apple's intention to cause Dr. Sagan or his family any embarrassment or concern."<ref name="Poundstone, pp. 374–375">[[#Poundstone|Poundstone 1999]], pp. 374–375</ref>

In 2019, Carl Sagan's daughter Sasha Sagan released ''For Small Creatures Such as We: Rituals for Finding Meaning in our Unlikely World'', which depicts life with her parents and her father's death when she was fourteen.<ref name="Ruth Frazier">{{cite journal |last1=Frazier |first1=Ruth |title=Finding Science and Wonder, Making Meaning |journal=Skeptical Inquirer |~~date~~year=2019 |volume=43 |issue=6 |pages=62–63}}</ref> Building on a theme in her father's work, Sasha Sagan argues in ''For Small Creatures Such as We'' that skepticism does not imply pessimism.<ref>{{Cite web |url=https://www.kveller.com/sasha-sagan-on-making-jewish-rituals-meaningful-for-secular-jews/ |title=Sasha Sagan on Making Jewish Rituals Meaningful for Secular Jews |date=October 23, 2019 |website=Kveller |language=en |access-date=November 6, 2019 |archive-date=November 6, 2019 |archive-url=https://web.archive.org/web/20191106082345/https://www.kveller.com/sasha-sagan-on-making-jewish-rituals-meaningful-for-secular-jews/ |url-status=live}}</ref>

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Sagan also commented on Christianity and the [[Jefferson Bible]], stating "My long-time view about Christianity is that it represents an amalgam of two seemingly immiscible parts, the religion of Jesus and the religion of [[Paul the Apostle|Paul]]. [[Thomas Jefferson]] attempted to excise the Pauline parts of the New Testament. There wasn't much left when he was done, but it was an inspiring document."<ref>{{cite book |last=Schei |first=Kenneth A. |title=An Atheist for Jesus |year=1996 |publisher=Synthesis |isbn=978-0-926491-01-4}}</ref>

Sagan thought that spirituality should be scientifically informed and that traditional religions should be abandoned and replaced with belief systems that revolve around the scientific method,<ref>{{Cite web |date=December 16, 2022 |title=Carl Sagan |url=https://www.britannica.com/biography/Carl-Sagan |access-date=March 21, 2023 |~~publisher~~work=[[Encyclopædia Britannica]] |language=en}}</ref> but also the mystery and incompleteness of scientific fields. Regarding spirituality and its relationship with science, Sagan stated: {{blockquote|'Spirit' comes from the Latin word 'to breathe'. What we breathe is air, which is certainly matter, however thin. Despite usage to the contrary, there is no necessary implication in the word 'spiritual' that we are talking of anything other than matter (including the matter of which the brain is made), or anything

outside the realm of science. On occasion, I will feel free to use the word. Science is not only compatible with spirituality; it is a profound source of spirituality. When we recognize our place in an immensity of light-years and in the passage of ages, when we grasp the intricacy, beauty, and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual.<ref>Sagan, Carl; Druyan, Ann (1997). [[The Demon-Haunted World: Science as a Candle in the Dark]]. Ballantine Books {{ISBN|0345409469}}</ref>}}

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== Death ==

[[File:Carl-sagan-brooklyn.JPG|thumb|right|Stone dedicated to Sagan in the Celebrity Path of the [[Brooklyn Botanic Garden]]]]

After suffering from [[Myelodysplastic syndrome|myelodysplasia]] for two years and receiving three [[Hematopoietic stem cell transplantation|bone marrow transplants]] from his sister, Sagan died from [[pneumonia]] at the age of 62 at the [[Fred Hutchinson Cancer Research Center]] in [[Seattle]] on December 20, 1996.<ref name="nyt"/><ref>{{cite news |first=Norma |last=Quarles |title=Carl Sagan dies at 62 |url=http://www.cnn.com/US/9612/20/sagan/ |~~work~~publisher=[[CNN]] |date=December 20, 1996 |access-date=December 5, 2011 |quote=Sagan was a noted astronomer whose lifelong passion was searching for intelligent life in the cosmos. |archive-date=March 11, 2010 |archive-url=https://web.archive.org/web/20100311184931/http://www.cnn.com/US/9612/20/sagan/ |url-status=live}}</ref> He was buried at [[Lake View Cemetery (Ithaca, New York)|Lake View Cemetery]] in [[Ithaca, New York]].

== Awards and honors ==

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* [[American Humanist Association#AHA's Humanists of the Year|Humanist of the Year]]—1981—Awarded by the [[American Humanist Association]]<ref>{{cite web |title=From the AHA archives: Carl Sagan's 1981 Humanist of the year speech |url=http://americanhumanist.org/HNN/details/2012-05-from-the-aha-archives-carl-sagans-1981-humanist-of-t |website=americanhumanist.org |access-date=December 25, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141226010015/http://americanhumanist.org/HNN/details/2012-05-from-the-aha-archives-carl-sagans-1981-humanist-of-t |archive-date=December 26, 2014}}</ref>

* [[American Philosophical Society]]—1995—Elected to membership.<ref>{{cite web |url=http://www.amphilsoc.org/memhist/search?creator=sagan&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |title=American Philosophical Society Member History |publisher=[[American Philosophical Society]] |location=Philadelphia, PA |access-date=September 3, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131113140231/http://www.amphilsoc.org/memhist/search?creator=sagan&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced |archive-date=November 13, 2013}}</ref>

* In Praise of Reason Award—1987—[[Committee for Skeptical Inquiry]]<ref name="Pasadena 1987">{{cite journal |last1=Shore |first1=Lys Ann |title=Controversies in Science and Fringe Science: From Animals and SETI to Quackery and SHC |journal=The Skeptical Inquirer |~~date~~year=1987 |volume=12 |issue=1 |pages=12–13}}</ref>

* [[Isaac Asimov Awards|Isaac Asimov Award]]—1994—[[Committee for Skeptical Inquiry]]<ref name="Seattle 1994">{{cite journal |last1=Karr |first1=Barry |author-link=Barry Karr |title=Five Honored with CSICOP Awards |journal=Skeptical Inquirer |~~date~~year=1994 |volume=18 |issue=5 |pages=461–462}}</ref>

* John F. Kennedy Astronautics Award—1982—[[American Astronautical Society]]<ref>{{cite web |url=http://www.astronautical.org/awards/kennedy |title=John F. Kennedy Astronautics Award |publisher=[[American Astronautical Society]] |location=Springfield, VA |access-date=September 3, 2013 |archive-date=September 19, 2013 |archive-url=https://web.archive.org/web/20130919002654/http://www.astronautical.org/awards/kennedy |url-status=live}}</ref>

* Special non-fiction [[John W. Campbell Memorial Award for Best Science Fiction Novel|Campbell Memorial Award]]—1974—''[[The Cosmic Connection: An Extraterrestrial Perspective]]''<ref>{{cite web |url=http://www.sfcenter.ku.edu/campbell.htm |title=The John W. Campbell Memorial Award |publisher=Center for the Study of Science Fiction |location=Lawrence, KS |access-date=September 3, 2013 |archive-date=December 29, 2012 |archive-url=https://web.archive.org/web/20121229102140/http://www.sfcenter.ku.edu/campbell.htm |url-status=live}}</ref>

* [[Joseph Priestley]] Award—"For distinguished contributions to the welfare of mankind"<ref name="Priestley_Award">{{cite web |title=Carl Sagan – 1975 |url=http://dh.dickinson.edu/philljai/1975-carl-sagan |website=The Joseph Priestley Award |publisher=Dickinson University |access-date=February 1, 2017 |archive-date=November 13, 2017 |archive-url=https://web.archive.org/web/20171113002948/http://dh.dickinson.edu/philljai/1975-carl-sagan |url-status=dead}}</ref>

* [[Klumpke-Roberts Award]] of the [[Astronomical Society of the Pacific]]—1974

* Golden Plate Award of the [[Academy of Achievement|American Academy of Achievement]]—1975<ref>{{cite web |title=Golden Plate Awardees of the American Academy of Achievement |website=~~www.~~achievement.org |publisher=[[American Academy of Achievement]] |url=https://achievement.org/our-history/golden-plate-awards/#science-exploration |access-date=May 21, 2020 |archive-date=December 15, 2016 |archive-url=https://web.archive.org/web/20161215023909/https://achievement.org/our-history/golden-plate-awards/#science-exploration |url-status=live}}</ref>

* [[Konstantin Tsiolkovsky]] Medal—Awarded by the Soviet Cosmonauts Federation

* [[Locus Award]] 1986—''Contact''

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* [[UCLA]] Medal–1991<ref>{{cite web |url=http://www.eventsprotocol.ucla.edu/documents/RECIPIENalpha.pdf |title=THE UCLA MEDAL RECIPIENTS, 1979 – PRESENT (ALPHABETICAL) |website=Eventsprotocol.ucla.edu |access-date=March 1, 2019 |archive-date=April 11, 2019 |archive-url=https://web.archive.org/web/20190411204900/http://www.eventsprotocol.ucla.edu/documents/RECIPIENalpha.pdf |url-status=live}}</ref>

* Inductee to [[International Space Hall of Fame]] in 2004<ref name=ep4>{{cite news |url=https://www.newspapers.com/clip/29988299/el_paso_times/ |title=X-Prize Group Founder to Speak at Induction |newspaper=El Paso Times |location=El Paso, Texas |date=October 17, 2004 |page=59 |via=Newspapers.com |access-date=March 27, 2019 |archive-date=December 23, 2019 |archive-url=https://web.archive.org/web/20191223114639/https://www.newspapers.com/clip/29988299/el_paso_times/ |url-status=live}}</ref>

* Named the "[[The Greatest American|99th Greatest American]]" on June 5, 2005, ''Greatest American'' [[Television program#Seasons/series|television series]] on the [[Discovery Channel]]<ref>{{cite web |title=Greatest American |url=https://www.imdb.com/title/tt0463820/ |~~website~~publisher=IMDb |access-date=September 2, 2019 |archive-date=September 22, 2020 |archive-url=https://web.archive.org/web/20200922054820/https://www.imdb.com/title/tt0463820/ |url-status=live}}</ref>

* Named an honorary member of the [[Demosthenian Literary Society]] on November 10, 2011

* [[New Jersey Hall of Fame]]—2009—Inductee.<ref>{{cite news |title=2009 New Jersey Hall of Fame inductees welcomed at NJPAC |first=Rohan |last=Mascarenhas |url=http://www.nj.com/news/index.ssf/2009/05/2009_new_jersey_hall_of_fame_i.html |newspaper=[[The Star-Ledger]] |location=Newark, NJ |date=May 3, 2009 |access-date=September 3, 2013 |archive-date=November 5, 2013 |archive-url=https://web.archive.org/web/20131105012448/http://www.nj.com/news/index.ssf/2009/05/2009_new_jersey_hall_of_fame_i.html |url-status=live}}</ref>

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=== Posthumous recognition ===

The 1997 film ''[[Contact (1997 American film)|Contact]]'' was based on the only novel Sagan wrote<ref>{{Cite web |url=https://www.publishersweekly.com/978-0-671-43400-7 |website=~~www.publishersweekly.com~~Publishers Weekly |access-date=November 6, 2019 |title=Fiction Book Review: Contact by Carl Sagan, Author Simon & Schuster $18.45 (0p) ISBN 978-0-671-43400-7 |date=October 1985 |archive-date=November 6, 2019 |archive-url=https://web.archive.org/web/20191106083007/https://www.publishersweekly.com/978-0-671-43400-7 |url-status=live}}</ref> and finished after his death. It ends with the dedication "For Carl." His photo can also be seen in the film.

In 1997, the [[Sagan Planet Walk]] was opened in Ithaca, New York. It is a walking-scale model of the Solar System, extending 1.2 km from the center of The Commons in downtown Ithaca to the [[Sciencenter]], a hands-on museum. The exhibition was created in memory of Carl Sagan, who was an Ithaca resident and Cornell Professor. Professor Sagan had been a founding member of the museum's advisory board.<ref>{{cite web |url=http://www.sciencenter.org/saganpw/ |title=Sagan Planet Walk |website=sciencenter.org |publisher=[[Sciencenter]] |location=Ithaca, NY |access-date=March 10, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130205135839/http://www.sciencenter.org/saganpw/ |archive-date=February 5, 2013}}</ref>

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* [https://www.youtube.com/watch?v=PQ4qBBWv3b4 Sagan interviewed by Ted Turner], CNN, 1989, video: 44 minutes.

* [https://www.bbc.co.uk/iplayer/episode/b00scvqk/Great_Lives_Series_21_Carl_Sagan/ Carl Sagan]—''Great Lives'', [[BBC Radio]], December 15, 2017

* [https://web.archive.org/web/20221018010748/https://books.google.~~com~~co.uk/books?id=HoZdcomupUQC&pg=PA36&hl=en#v=onepage&q&f=false "A man whose time has come"]—Interview with Carl Sagan by [[Ian Ridpath]], ''[[New Scientist]]'', July 4, 1974

* {{IMDb name|755981|Carl Sagan}}

* [https://web.archive.org/web/20160201115954/http://www.csicop.org/si/show/carl_sagans_life_and_legacy_as_scientist_teacher_and_skeptic "Carl Sagan's Life and Legacy as Scientist, Teacher, and Skeptic"], by David Morrison, [[Committee for Skeptical Inquiry]]

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[[Category:American cannabis activists]]

[[Category:American cosmologists]]

[[Category:American critics of alternative medicine]]▼

[[Category:American critics of creationism]]▼

[[Category:American humanists]]

[[Category:American male non-fiction writers]]

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[[Category:American people of Russian-Jewish descent]]

[[Category:American people of Ukrainian-Jewish descent]]

[[Category:American planetary scientists]]▼

[[Category:American science fiction writers]]

[[Category:American science writers]]

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[[Category:Burials in New York (state)]]

[[Category:Cornell University faculty]]

▲[[Category:American critics of alternative medicine]]

▲[[Category:American critics of creationism]]

[[Category:Critics of parapsychology]]

[[Category:Deaths from myelodysplastic syndrome]]

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[[Category:Hugo Award-winning writers]]

[[Category:Interstellar messages]]

[[Category:Jewish American activists]]▼

[[Category:Jewish agnostics]]

▲[[Category:Jewish American activists]]

[[Category:Jewish American scientists]]

[[Category:Jewish astronomers]]

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[[Category:People associated with the American Museum of Natural History]]

[[Category:People from Bensonhurst, Brooklyn]]

▲[[Category:American planetary scientists]]

[[Category:Presidents of The Planetary Society]]

[[Category:Pulitzer Prize for General Non-Fiction winners]]