Democritus

Democritus
Born	ca. 460 BC Abdera, Thrace
Died	ca. 370 BC (Aged 90)
Era	Pre-Socratic philosophy
Region	Western Philosophy
School	Pre-Socratic philosophy
Main interests	metaphysics / mathematics / astronomy
Notable ideas	atomism, distant star theory
Influenced by Leucippus, Melissus of Samos
Influenced Epicurus, Pyrrho, Lucretius, Santayana, Aristotle

Democritus (Greek: Δημόκριτος, Dēmokritos, "chosen of the people") (ca. 460 BC – ca. 370 BC) was an Ancient Greek philosopher born in Abdera, Thrace, Greece.^[1] He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos.^[2]

His exact contributions are difficult to disentangle from his mentor Leucippus, as they are often mentioned together in texts. Their speculation on atoms, taken from Leucippus, bears a passing and partial resemblance to the nineteenth-century understanding of atomic structure that has led some to regard Democritus as more of a scientist than other Greek philosophers; however their ideas rested on very different bases.^[3] Largely ignored in ancient Athens, Democritus was nevertheless well known to his fellow northern-born philosopher Aristotle. Plato is said to have disliked him so much that he wished all his books burned.^[1] Many consider Democritus to be the "father of modern science".^[4]

Life[link]

Democritus was born in the city of Abdera in Thrace, an Ionian colony of Teos,^[5] although some called him a Milesian.^[6] He was born in the 80th Olympiad (460–457 BC) according to Apollodorus of Athens,^[7] and although Thrasyllus placed his birth in 470 BC,^[7] the later date is probably more likely.^[8] John Burnet has argued that the date of 460 is "too early", since according to Diogenes Laërtius ix.41, Democritus said that he was a "young man (neos)" during Anaxagoras' old age (circa 440–428).^[9] It was said that Democritus' father was so wealthy that he received Xerxes on his march through Abdera. Democritus spent the inheritance which his father left him on travels into distant countries, to satisfy his thirst for knowledge. He traveled to Asia, and was even said to have reached India and Ethiopia.^[10]

Democritus, by Hendrick ter Brugghen, 1628.

We know that he wrote on Babylon and Meroe; he must also have visited Egypt, and Diodorus Siculus states that he lived there for five years.^[11] He himself declared^[12] that among his contemporaries none had made greater journeys, seen more countries, and met more scholars than himself. He particularly mentions the Egyptian mathematicians, whose knowledge he praises. Theophrastus, too, spoke of him as a man who had seen many countries.^[13] During his travels, according to Diogenes Laërtius, he became acquainted with the Chaldean magi. A certain "Ostanes", one of the magi accompanying Xerxes was also said to have taught him.^[14]

After returning to his native land he occupied himself with natural philosophy. He traveled throughout Greece to acquire a knowledge of its culture. He mentions many Greek philosophers in his writings, and his wealth enabled him to purchase their writings. Leucippus, the founder of the atomism, was the greatest influence upon him. He also praises Anaxagoras.^[15] Diogenes Laertius says that he was friends with Hippocrates.^[16] He may have been acquainted with Socrates, but Plato does not mention him and Democritus himself is quoted as saying, "I came to Athens and no one knew me."^[17] Aristotle placed him among the pre-Socratic natural philosophers.^[18]

Rembrandt, The Young Rembrandt as Democritus the Laughing Philosopher (1628-1629).

The many anecdotes about Democritus, especially in Diogenes Laërtius, attest to his disinterest, modesty, and simplicity, and show that he lived exclusively for his studies. One story has him deliberately blinding himself in order to be less disturbed in his pursuits;^[19] it may well be true that he lost his sight in old age. He was cheerful, and was always ready to see the comical side of life, which later writers took to mean that he always laughed at the foolishness of people.^[20]

He was highly esteemed by his fellow-citizens, "because," as Diogenes Laërtius says, "he had foretold them some things which events proved to be true," which may refer to his knowledge of natural phenomena. According to Diodorus Siculus,^[21] Democritus died at the age of 90, which would put his death around 370 BC, but other writers have him living to 104,^[22] or even 109.^[23]

Popularly known as the Laughing Philosopher (for laughing at human follies), the terms Abderitan laughter, which means scoffing, incessant laughter, and Abderite, which means a scoffer, are derived from Democritus.^[24] To his fellow citizens he was also known as "The Mocker".

Philosophy and science[link]

Democritus followed in the tradition of Leucippus, who seems to have come from Miletus, and he carried on the scientific rationalist philosophy associated with that city. They were both strict determinists and thorough materialists, believing everything to be the result of natural laws. Unlike Aristotle or Plato, the atomists attempted to explain the world without reasoning to purpose, prime mover, or final cause. For the atomists questions should be answered with a mechanistic explanation ("What earlier circumstances caused this event?"), while their opponents search for explanations which, in addition to the material and mechanistic, also included the formal and teleological ("What purpose did this event serve?"). Modern science has focused on mechanistic questions, which have led to scientific knowledge, especially in physics, while teleological questions can be useful in biology, in adaptationist reasoning at providing proximate explanations, though the deeper evolutionary explanations are often held to be thoroughly mechanistic. The atomists looked exclusively for mechanistic questions, and only admitted mechanistic answers. Their successors until the Renaissance became occupied with the teleological question, which arguably hindered progress.^[25]

Democritus meditating on the seat of the soul by Léon-Alexandre Delhomme, 1868

Atomic hypothesis[link]

The theory of Democritus and Leucippus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. Of the mass of atoms, Democritus said "The more any indivisible exceeds, the heavier it is." But his exact position on weight of atoms is disputed.^[1]

Leucippus is widely credited with being the first to develop the theory of atomism, although Isaac Newton preferred to credit the obscure Moschus the Phoenician (whom he believed to be the biblical Moses) as the inventor of the idea on the authority of Posidonius and Strabo.^[26] The Stanford Encyclopedia of Philosophy notes, "This theologically motivated view does not seem to claim much historical evidence, however."^[27]

Democritus, along with Leucippus and Epicurus, proposed the earliest views on the shapes and connectivity of atoms. They reasoned that the solidness of the material corresponded to the shape of the atoms involved. Thus, iron atoms are solid and strong with hooks that lock them into a solid; water atoms are smooth and slippery; salt atoms, because of their taste, are sharp and pointed; and air atoms are light and whirling, pervading all other materials.^[28] Democritus was the main proponent of this view. Using analogies from our sense experiences, he gave a picture or an image of an atom that distinguished them from each other by their shape, their size, and the arrangement of their parts. Moreover, connections were explained by material links in which single atoms were supplied with attachments: some with hooks and eyes others with balls and sockets.^[29] The Democritean atom is an inert solid (merely excluding other bodies from its volume) that interacts with other atoms mechanically. In contrast, modern, quantum-mechanical atoms interact via electric and magnetic force fields and are far from inert.

The theory of the atomists appears to be more nearly aligned with that of modern science than any other theory of antiquity. However, the similarity with modern concepts of science can be confusing when trying to understand where the hypothesis came from. It is obvious that classical atomists would never have had a solid empirical basis for our modern concepts of atoms and molecules. Bertrand Russell states that they just hit on a lucky hypothesis, only recently confirmed by evidence.^[30] However Lucretius, describing atomism in his De rerum natura gives very clear and compelling empirical arguments for the original atomist theory. He observes that any material is subject to irreversible decay. Through time, even hard rocks are slowly worn down by drops of water. Things have the tendency to get mixed up: mix water with soil and you get mud, that will usually not un-mix by itself. Wood decays. However, we see in nature and technology that there are mechanisms to recreate 'pure' materials like water, air, metals.^{[citation needed]} The seed of an oak will grow out into an oak tree, made of similar wood as historical oak trees, the wood of which has already decayed. The conclusion is that many properties of materials must derive from something inside, that will itself never decay, something that stores for eternity the same inherent, indivisible properties. The basic question is: why has everything in the world not yet decayed, and how can exactly the same materials, plants, animals be recreated again and again? One obvious solution to explain how indivisible properties can be conveyed in a way not easily visible to human senses, is to hypothesise the existence of 'atoms'. These classical 'atoms' are nearer to our modern concept of 'molecule' than to the atoms of modern science.^{[citation needed]} The other big point of classical atomism is that there must be a lot of open space between these 'atoms': the void. Lucretius gives reasonable arguments^{[citation needed]} that the void is absolutely necessary to explain how gasses and fluids can change shape, flow, while metals can be molded, without changing the basic material properties

Void hypothesis[link]

The atomistic void hypothesis was a response to the paradoxes of Parmenides and Zeno, the founders of metaphysical logic, who put forth difficult to answer arguments in favor of the idea that there can be no movement. They held that any movement would require a void—which is nothing—but a nothing cannot exist. The Parmenidean position was "You say there 'is' a void; therefore the void is not nothing; therefore there is not the void." The position of Parmenides appeared validated by the observation that where there seems to be nothing there is air, and indeed even where there is not matter there is something, for instance light waves.

The atomists agreed that motion required a void, but simply ignored the argument of Parmenides on the grounds that motion was an observable fact. Therefore, they asserted, there must be a void. This idea survived in a refined version as Newton's theory of absolute space, which met the logical requirements of attributing reality to not-being. Einstein's theory of relativity provided a new answer to Parmenides and Zeno, with the insight that space by itself is relative and cannot be separated from time as part of a generally curved space-time manifold. Consequently, Newton's refinement is now considered superfluous.^[31]

Epistemology[link]

The knowledge of truth according to Democritus is difficult, since the perception through the senses is subjective. As from the same senses derive different impressions for each individual, then through the sense-impressions we cannot judge the truth. We can only interpret the sense data through the intellect and grasp the truth, because the truth (aletheia) is at the bottom (en bythoe).

“And again, many of the other animals receive impressions contrary to ours; and even to the senses of each individual, things do not always seem the same. Which then, of these impressions are true and which are false is not obvious; for the one set is no more true than the other, but both are alike. And this is why Democritus, at any rate, says that either there is no truth or to us at least it is not evident.”^[32]

“Democritus says: By convention hot, by convention cold, but in reality atoms and void, and also in reality we know nothing, since the truth is at bottom.”^[33]

There are two kinds of knowing, the one he calls “legitimate” (gnesie: genuine) and the other “bastard” (skotie: obscure). The “bastard” knowledge is concerned with the perception through the senses, therefore it is insufficient and subjective. The reason is that the sense-perception is due to the effluences of the atoms (aporroai) from the objects to the senses. When these different shapes of atoms come to us, they stimulate our senses according to their shape, and our sense-impressions arise from those stimulations.^[34]

The second sort of knowledge, the “legitimate” one, can be achieved through the intellect, in other words, all the sense-data from the “bastard” must be elaborated through reasoning. In this way one can get away from the false perception of the “bastard” knowledge and grasp the truth through the inductive reasoning. After taking into account the sense-impressions, one can examine the causes of the appearances, draw conclusions about the laws that govern the appearances, and discover the causality (aetiologia) by which they are related. This is the procedure of thought from the parts to the whole or else from the apparent to non-apparent (inductive reasoning). This is one example of why Democritus is considered to be an early scientific thinker. The process is reminiscent of that by which science gathers its conclusions.

“But in the Canons Democritus says there are two kinds of knowing, one through the senses and the other through the intellect. Of these he calls the one through the intellect ‘legitimate’ attesting its trustworthiness for the judgement of truth, and through the senses he names ‘bastard’ denying its inerrancy in the discrimination of what is true. To quote his actual words: Of knowledge there are two forms, one legitimate, one bastard. To the bastard belong all this group: sight, hearing, smell, taste, touch. The other is legitimate and separate from that. Then, preferring the legitimate to the bastard, he continues: When the bastard can no longer see any smaller, or hear, or smell, or taste, or perceive by touch, but finer matters have to be examined, then comes the legitimate, since it has a finer organ of perception.”^[35]

“In the Confirmations ... he says: But we in actuality grasp nothing for certain, but what shifts in accordance with the condition of the body and of the things (atoms) which enter it and press upon it.”^[36]

“Democritus used to say that 'he prefers to discover a causality rather than become a king of Persia'.”^[37]

Ethics and politics[link]

Crying Heraclitus and laughing Democritus, from a 1477 Italian fresco, Pinacoteca di Brera, Milan.

The ethics and politics of Democritus come to us mostly in the form of maxims. He says that "Equality is everywhere noble," but he is not encompassing enough to include women or slaves in this sentiment. Poverty in a democracy is better than prosperity under tyrants, for the same reason one is to prefer liberty over slavery. Those in power should "take it upon themselves to lend to the poor and to aid them and to favor them, then is there pity and no isolation but companionship and mutual defense and concord among the citizens and other good things too many to catalogue." Money when used with sense leads to generosity and charity, while money used in folly leads to a common expense for the whole society— excessive hoarding of money for one's children is avarice. While making money is not useless, he says, doing so as a result of wrong-doing is the "worst of all things." He is on the whole ambivalent towards wealth, and values it much less than self-sufficiency. He disliked violence but was not a pacifist: he urged cities to be prepared for war, and believed that a society had the right to execute a criminal or enemy so long as this did not violate some law, treaty, or oath.^[2][31]

Goodness, he believed, came more from practice and discipline than from innate human nature. He believed that one should distance oneself from the wicked, stating that such association increases disposition to vice. Anger, while difficult to control, must be mastered in order for one to be rational. Those who take pleasure from the disasters of their neighbors fail to understand that their fortunes are tied to the society in which they live, and they rob themselves of any joy of their own. He advocated a life of contentment with as little grief as possible, which he said could not be achieved through either idleness or preoccupation with worldly pleasures. Contentment would be gained, he said, through moderation and a measured life; to be content one must set their judgment on the possible and be satisfied with what one has—giving little thought to envy or admiration. Democritus approved of extravagance on occasion, as he held that feasts and celebrations were necessary for joy and relaxation. He considers education to be the noblest of pursuits, but cautioned that learning without sense leads to error.^[2][31]

Mathematics[link]

A right circular cone and an oblique circular cone

Democritus was also a pioneer of mathematics and geometry in particular. We only know this through citations of his works (titled On Numbers, On Geometrics, On Tangencies, On Mapping, and On Irrationals) in other writings, since most of Democritus' body of work did not survive the Middle Ages. Democritus was among the first to observe that a cone or pyramid has one-third the volume of a cylinder or prism respectively with the same base and height. Also, a cone divided in a plane parallel to its base produces two surfaces. He pointed out that if the two surfaces are commensurate with each other, then the shape of the body would appear to be a cylinder, as it is composed of equal rather than unequal circles. However, if the surfaces are not commensurate, then the side of a cone is not smooth but jagged like a series of steps.^[38]

Anthropology, biology, and cosmology[link]

His work on nature is known through citations of his books on the subjects, On the Nature of Man, On Flesh (two books), On Mind, On the Senses, On Flavors, On Colors, Causes concerned with Seeds and Plants and Fruits, and Causes concerned with Animals (three books).^[2] He spent much of his life experimenting with and examining plants and minerals, and wrote at length on many scientific topics.^[39] Democritus thought that the first humans lived an anarchic and animal sort of life, going out to forage individually and living off the most palatable herbs and the fruit which grew wild on the trees. They were driven together into societies for fear of wild animals, he said. He believed that these early people had no language, but that they gradually began to articulate their expressions, establishing symbols for every sort of object, and in this manner came to understand each other. He says that the earliest men lived laboriously, having none of the utilities of life; clothing, houses, fire, domestication, and farming were unknown to them. Democritus presents the early period of mankind as one of learning by trial and error, and says that each step slowly led to more discoveries; they took refuge in the caves in winter, stored fruits that could be preserved, and through reason and keenness of mind came to build upon each new idea.^[2][40]

Democritus held that the Earth was round, and stated that originally the universe was composed of nothing but tiny atoms churning in chaos, until they collided together to form larger units—including the earth and everything on it.^[2] He surmised that there are many worlds, some growing, some decaying; some with no sun or moon, some with several. He held that every world has a beginning and an end, and that a world could be destroyed by collision with another world. To epitomize Democritus's cosmology, Russell calls on Shelley: "Worlds on worlds are rolling ever / From creation to decay, / Like the bubbles on a river / Sparkling, bursting, borne away."^[41]

Works[link]

Ethics

• Pythagoras
• On the Disposition of the Wise Man
• On the Things in Hades
• Tritogenia
• On Manliness or On Virtue
• The Horn of Amaltheia
• On Contentment
• Ethical Commentaries

Natural science

• The Great World-ordering (may have been written by Leucippus)
• Cosmography
• On the Planets
• On Nature
• On the Nature of Man or On Flesh (two books)
• On the Mind
• On the Senses
• On Flavours
• On Colours
• On Different Shapes
• On Changing Shape
• Buttresses
• On Images
• On Logic (three books)

Nature

• Heavenly Causes
• Atmospheric Causes
• Terrestrial Causes
• Causes Concerned with Fire and Things in Fire
• Causes Concerned with Sounds
• Causes Concerned with Seeds and Plants and Fruits
• Causes Concerned with Animals (three books)
• Miscellaneous Causes
• On Magnets

Mathematics

• On Different Angles or On contact of Circles and Spheres
• On Geometry
• Geometry
• Numbers
• On Irrational Lines and Solids (two books)
• Planispheres
• On the Great Year or Astronomy (a calendar)
• Contest of the Waterclock
• Description of the Heavens
• Geography
• Description of the Poles
• Description of Rays of Light

Literature

• On the Rhythms and Harmony
• On Poetry
• On the Beauty of Verses
• On Euphonious and Harsh-sounding Letters
• On Homer
• On Song
• On Verbs
• Names

Technical works

• Prognosis
• On Diet
• Medical Judgment
• Causes Concerning Appropriate and Inappropriate Occasions
• On Farming
• On Painting
• Tactics
• Fighting in Armor

Commentaries

• On the Sacred Writings of Babylon
• On Those in Meroe
• Circumnavigation of the Ocean
• On History
• Chaldaean Account
• Phrygian Account
• On Fever and Coughing Sicknesses
• Legal Causes
• Problems^[42]

Eponymous Institutions[link]

• Democritus University of Thrace
• National Centre of Scientific Research "DEMOKRITOS"

Numismatics[link]

Greek ten drachma coin

Democritus was depicted on the following contemporary coins/banknotes:

• The reverse of the Greek 10 drachmas coin of 1976–2001.^[43]
• The obverse of the Greek 100 drachmas banknote of 1967–1978.^[44]

See also[link]

• Atom
• John Dalton
• Kanada
• Leucippus
• Mochus
• Vaisheshika

Footnotes[link]

References[link]

• Bailey, C. (1928). The Greek Atomists and Epicurus. Oxford.
• Bakalis, Nikolaos (2005). Handbook of Greek Philosophy: From Thales to the Stoics: Analysis and Fragments, Trafford Publishing, ISBN 1-4120-4843-5.
• Barnes, Jonathan (1982). The Presocratic Philosophers, Routledge Revised Edition.
• _____ (1987). Early Greek Philosophy, Penguin.
• Burnet, J. (2003). Early Greek Philosophy, Kessinger Publishing
• Diodorus Siculus (1st century BC). Bibliotheca historica.
• Diogenes Laërtius (3rd century AD). Lives and Opinions of Eminent Philosophers.
• Freeman, Kathleen (2008). Ancilla to the Pre-Socratic Philosophers: A Complete Translation of the Fragments in Diels, Forgotten Books, ISBN 978-1-60680-256-4.
• Guthrie, W. K. (1979) A History of Greek Philosophy – The Presocratic tradition from Parmenides to Democritus, Cambridge University Press.
• Kirk, G. S., J. E. Raven and M. Schofield (1983). The Presocratic Philosophers, Cambridge University Press, 2nd edition.
• Melchert, Norman (2002). The Great Conversation: A Historical Introduction to Philosophy. McGraw Hill. ISBN 0-19-517510-7. 
• P|yle, C. M. (1997). 'Democritus and Heracleitus: An Excursus on the Cover of this Book,' Milan and Lombardy in the Renaissance. Essays in Cultural History. Rome, La Fenice. (Istituto di Filologia Moderna, Università di Parma: Testi e Studi, Nuova Serie: Studi 1.) (Fortuna of the Laughing and Weeping Philosophers topos)
• Petronius (late 1st century AD). Satyricon. Trans. William Arrowsmith. New York: A Meridian Book, 1987.
• Russell, Bertrand (1972). A History of Western Philosophy, Simon & Schuster.
• Sextus Empiricus (ca. 200 AD). Adversus Mathematicos.

Further reading[link]

• Brumbaugh, Robert S. (1964). The Philosophers of Greece. New York: Crowell. 
• Burnet, John (1914). Greek Philosophy: Thales to Plato. London: Macmillan. http://books.google.com/books?id=9vc_AAAAYAAJ. 
• Sandywell, Barry (1996). Presocratic reflexivity : the construction of philosophical discourse c. 600 - 450 BC. London: Routledge. ISBN 0-415-10170-0. 
• Vlastos, Gregory (1945/1946). "Ethics and Physics in Democritus". Philosophical Review 54/55: 578–592, 53–64. 

External links[link]

Wikiquote has a collection of quotations related to: Democritus

Wikimedia Commons has media related to: Democritus

• Democritus entry by Sylvia Berryman in the Stanford Encyclopedia of Philosophy
• Democritus entry in the Internet Encyclopedia of Philosophy
• O'Connor, John J.; Robertson, Edmund F., "Democritus", MacTutor History of Mathematics archive, University of St Andrews, http://www-history.mcs.st-andrews.ac.uk/Biographies/Democritus.html .
• Democritus and Leucippus - thebigview.com
• Diogenes Laërtius, Life of Democritus, translated by Robert Drew Hicks (1925).

Carl Sagan
Sagan in 1980
Born	(1934-11-09)November 9, 1934 Brooklyn, New York, U.S.
Died	December 20, 1996(1996-12-20) (aged 62) Seattle, Washington, U.S.
Residence	United States[1]
Nationality	United States
Fields	Astronomy, astrophysics, cosmology, astrobiology, space science, planetary science
Institutions	Cornell University Harvard University Smithsonian Astrophysical Observatory University of California, Berkeley
Alma mater	University of Chicago (B.A.), (B.Sc.), (M.Sc.), (PhD)
Known for	Search for Extra-Terrestrial Intelligence (SETI) Cosmos: A Personal Voyage Cosmos Voyager Golden Record Pioneer plaque Contact Pale Blue Dot
Notable awards	NASA Distinguished Public Service Medal (1977) Pulitzer Prize for General Non-Fiction (1978) Oersted Medal (1990) National Academy of Sciences Public Welfare Medal (1994)

Carl Edward Sagan ( /ˈseɪɡɪn/; November 9, 1934 – December 20, 1996) was an American astronomer, astrophysicist, cosmologist, author, science popularizer, and science communicator in astronomy and natural sciences. He published more than 600 scientific papers^[2] and articles and was author, co-author or editor of more than 20 books. He advocated scientifically skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI).

Sagan is known for his popular science books and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote.^[3] The book Cosmos was published to accompany the series. Sagan wrote the novel Contact, the basis for a 1997 film of the same name.

Early life[link]

Carl Sagan was born in Brooklyn, New York,^[4] to a Ukrainian Jewish family. His father, Sam Sagan, was an immigrant garment worker from Kamenets-Podolsk, Ukraine;^[5] his mother, Rachel Molly Gruber, a housewife. Carl was named in honor of Rachel's biological mother, Chaiya Clara, in Sagan's words, "the mother she never knew." Sagan graduated from Rahway High School in Rahway, New Jersey, in 1951.^[6]

He had a sister, Carol, and the family lived in a modest apartment near the Atlantic Ocean, in Bensonhurst, a Brooklyn neighborhood. According to Sagan, they were Reform Jews, the most liberal of the three main Jewish groups. Both Sagan and his sister agree that their father was not especially religious, but that their mother "definitely believed in God, and was active in the temple ... and served only Kosher meat."^[6]:12 During the height of the Depression, his father had to accept a job as a theater usher.

According to biographer Keay Davidson, Sagan's "inner war" was a result of his close relations with both his parents, who were in many ways "opposites." Sagan traced his later analytical urges to his mother, a woman who had known "extreme poverty as a child," and had grown up almost homeless in New York City during World War I and the 1920s.^[6]:2 She had her own intellectual ambitions as a young woman, but they were blocked by social restrictions, because of her poverty, her being a woman and wife, and her Jewish ethnicity. Davidson notes that she therefore "worshiped her only son, Carl. He would fulfill her unfulfilled dreams."^[6]:2

However, his "sense of wonder" came from his father, who was a "quiet and soft-hearted escapee from the Czar." In his free time, he gave apples to the poor, or helped soothe labor-management tensions within New York's "tumultuous" garment industry.^[6]:2 Although he was "awed" by Carl's "brilliance, his boyish chatter about stars and dinosaurs," he took his son's inquisitiveness in stride, as part of his growing up.^[6]:2 In his later years as a writer and scientist, Sagan would often draw on his childhood memories to illustrate scientific points, as he did in his book, Shadows of Forgotten Ancestors.^[6]:9 Sagan describes his parents' influence on his later thinking:

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.^[7]

1939 World's Fair[link]

Sagan recalls that one of his best experiences was when he was four or five years old, his parents took him to the 1939 New York World's Fair. The exhibits became a turning point in his life. He later recalled the moving map of the "America of Tomorrow" exhibit: "It showed beautiful highways and cloverleaves and little General Motors cars all carrying people to skyscrapers, buildings with lovely spires, flying buttresses—and it looked great!"^[6]:14 At other exhibits, he remembered how a flashlight that shined on a photoelectric cell created a cracking sound, and how the sound from a tuning fork became a wave on an oscilloscope. He also witnessed the future media technology that would replace radio: television. Sagan 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?^[6]:14

He also saw one of the Fair's most publicized events, the burial of a time capsule at Flushing Meadows, which contained mementos of the 1930s to be recovered by Earth's descendants in a future millennium. "The time capsule thrilled Carl," writes Davidson. As an adult, Sagan and his colleagues created similar time capsules, but ones that would be sent out into the galaxy. These were the Pioneer plaque and the Voyager Golden Record records, all of which were spinoffs of Sagan's memories of the World Fair.^[6]:15

World War II[link]

During World War II, Sagan's family worried about the fate of their European relatives. Sagan, however, was generally unaware of the details of the ongoing war. He writes, "Sure, we had relatives who were caught up in the Holocaust. 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."^[6]: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.^[7]

Inquisitiveness about nature[link]

Soon after entering elementary school, he began to express a strong inquisitiveness about nature. Sagan recalled taking his first trips to the public library alone, at the age of 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.^[6]:18

About the time he was six or seven, he and a close friend took trips to the American Museum of Natural History in New York City. While there, they went to the Hayden Planetarium and walked around the museum's exhibits of space objects, such as meteorites, and displays of dinosaurs and animals in natural settings. Sagan writes about those visits:

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.^[6]:18

His parents helped nurture his growing interest in science by buying him chemistry sets and reading materials.^[8] His interest in space, however, was his primary focus, especially after reading science fiction stories by writers such as Edgar Rice Burroughs, which stirred his imagination about life on other planets, such as Mars. According to biographer Ray Spangenburg, these early years as Sagan tried 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."^[7]

Education and scientific career[link]

He attended the University of Chicago, where he participated in the Ryerson Astronomical Society,^[9] received a bachelor of arts in self-proclaimed "nothing" with general and special honors in 1954, a bachelor of science in physics in 1955, and a master of science in physics in 1956 before earning a PhD in astronomy and astrophysics in 1960.^[10][11][12] During his time as an honors program undergraduate, Sagan worked in the laboratory of the geneticist H. J. Muller and wrote a thesis on the origins of life with physical chemist H.C. Urey. From 1960 to 1962 Sagan was a Miller Fellow at the University of California, Berkeley. From 1962 to 1968, he worked at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts.

Sagan lectured and did research at Harvard University until 1968, when he moved to Cornell University in Ithaca, New York. He became a full Professor at Cornell in 1971, and he directed the Laboratory for Planetary Studies there. From 1972 to 1981, Sagan was the Associate Director of the Center for Radio Physics and Space Research at Cornell.

Sagan was associated with the US space program from its inception. From the 1950s onward, he worked as an advisor to NASA, where one of his duties included briefing the Apollo astronauts 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. He conceived the idea of adding an unalterable and universal message on spacecraft destined to leave the solar system that could potentially be understood by any extraterrestrial intelligence that might find it. Sagan assembled the first physical message that was sent into space: a gold- anodized 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 that was sent out with the Voyager space probes in 1977. Sagan often challenged the decisions to fund the Space Shuttle and Space Station at the expense of further robotic missions.^[13]

Sagan taught a course on critical thinking at Cornell University until he died in 1996 from pneumonia, a few months after finding that he was in remission of myelodysplastic syndrome.

Scientific achievements[link]

Sagan's contributions were central to the discovery of the high surface temperatures of the planet Venus. In the early 1960s no one knew for certain the basic conditions of that planet's surface, and Sagan listed the possibilities in a report later depicted for popularization in a Time-Life book, Planets. His own view was that Venus was dry and very hot as opposed to the balmy paradise others had imagined. He had investigated radio emissions from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA's Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his conclusions on the surface conditions of Venus in 1962.

Sagan was among the first to hypothesize that Saturn's moon Titan might possess oceans of liquid compounds on its surface and that Jupiter's moon Europa might possess subsurface oceans of water. This would make Europa potentially habitable.^[14] Europa's subsurface ocean of water was later indirectly confirmed by the spacecraft Galileo. The mystery of Titan's reddish haze was also solved with Sagan's help. The reddish haze was revealed to be due to complex organic molecules constantly raining down onto Titan's surface.^[15]

He further contributed insights regarding the atmospheres of Venus and Jupiter as well as seasonal changes on Mars. Sagan established that the atmosphere of Venus is extremely hot and dense with pressures increasing steadily all the way down to the surface. He also perceived global warming as a growing, man-made danger and likened it to the natural development of Venus into a hot, life-hostile planet through a kind of runaway greenhouse effect. Sagan and his Cornell colleague Edwin Ernest Salpeter speculated about life in Jupiter's clouds, given the planet's dense atmospheric composition rich in organic molecules. He studied the observed color variations on Mars' surface and concluded that they were not seasonal or vegetational changes as most believed but shifts in surface dust caused by windstorms.

Sagan is best known, however, for his research on the possibilities of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.^[16]

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."^[17] He was denied membership in the Academy, reportedly because his media activities made him unpopular with many other scientists.^[18]

Scientific advocacy[link]

Planetary Society members at the organization's founding. Carl Sagan is seated on the right.

Sagan's ability to convey his ideas allowed many people to better understand the cosmos—simultaneously emphasizing the value and worthiness of the human race, and the relative insignificance of the Earth in comparison to the universe. He delivered the 1977 series of Royal Institution Christmas Lectures in London.^[19] He hosted and, with Ann Druyan, co-wrote and co-produced the highly popular thirteen-part PBS television series Cosmos: A Personal Voyage modeled on Jacob Bronowski's The Ascent of Man.

Cosmos covered a wide range of scientific subjects including the origin of life and a perspective of our place in the universe. The series was first broadcast by the Public Broadcasting Service in 1980, winning an Emmy and a Peabody Award. It has been broadcast in more than 60 countries and seen by over 500 million people,^[3][20] making it the most widely watched PBS program in history.^[21] In addition, Time magazine ran a cover story about Sagan soon after the show broadcast, referring to him as "creator, chief writer and host-narrator of the new public television series Cosmos, [and] takes the controls of his fantasy spaceship."^[22]

Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with radio telescopes for signals from potential intelligent extraterrestrial life-forms. Sagan was so persuasive that by 1982 he was able to get a petition advocating SETI published in the journal Science and signed by 70 scientists including seven Nobel Prize winners. This was a tremendous increase in the respectability of this controversial field. Sagan also helped Dr. Frank Drake write the Arecibo message, a radio message beamed into space from the Arecibo radio telescope on November 16, 1974, aimed at informing potential extraterrestrials about Earth.

Sagan was chief technology officer of the professional planetary research journal Icarus for twelve years. He co-founded the Planetary Society, the largest space-interest group in the world, with over 100,000 members in more than 149 countries, and was a member of the SETI Institute Board of Trustees. Sagan served as Chairman of the Division for Planetary Science of the American Astronomical Society, as President of the Planetology Section of the American Geophysical Union, and as Chairman of the Astronomy Section of the American Association for the Advancement of Science.

At the height of the Cold War, Sagan became involved in public awareness efforts for the effects of nuclear war when a mathematical climate model suggested that a substantial nuclear exchange could upset the delicate balance of life on Earth. He was one of five authors—the "S" of the "TTAPS" report as the research paper came to be known. He eventually co-authored the scientific paper hypothesizing a global nuclear winter following nuclear war.^[23] He also co-authored the book A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, a comprehensive examination of the phenomenon of nuclear winter.

Sagan also wrote books to popularize science which reflected and expanded upon some of the themes of A Personal Voyage, and became the best-selling science book ever published in English;^[24] The Dragons of Eden: Speculations on the Evolution of Human Intelligence, which won a Pulitzer Prize; and Broca's Brain: Reflections on the Romance of Science. Sagan also wrote the best-selling science fiction novel Contact in 1985, based on a film treatment he wrote with his wife in 1979, but he did not live to see the book's 1997 motion picture adaptation, which starred Jodie Foster and won the 1998 Hugo Award for Best Dramatic Adaption.

Pale Blue Dot: Earth is a bright pixel when photographed from "Voyager 1" six billion kilometers out (past Pluto). Sagan encouraged NASA to generate this image.

He wrote a sequel to Cosmos, 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' Charlie Rose program in January 1995.^[25] Sagan also wrote an introduction for the bestselling book by Stephen Hawking, 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 debunking of the Betty and Barney Hill abduction. To mark the tenth anniversary of Sagan's death, 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.^[26]

Sagan hypothesized in January 1991 that enough smoke from the 1991 Kuwaiti oil fires "might get so high as to disrupt agriculture in much of South Asia ..." He later conceded in The Demon-Haunted World that this 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."^[27] A 2007 study noted that modern computer models have been applied to the Kuwait oil fires, finding that individual smoke plumes are not able to loft smoke into the stratosphere, but that smoke from fires covering a large area, like some forest fires or the burning of cities that would be expected to follow a nuclear strike, would loft significant amounts of smoke into the stratosphere.^{[28][29][30][31]}

In his later years Sagan advocated the creation of an organized search for near Earth objects that might impact the Earth.^[32] When others suggested creating large nuclear bombs that could be used to alter the orbit of a NEO that was predicted to hit the Earth, Sagan proposed the Deflection Dilemma: If we create the ability to deflect an asteroid away from the Earth, then we also create the ability to deflect an asteroid towards the Earth—providing an evil power with a true doomsday bomb.^[33][34]

Billions and billions[link]

Sagan with a model of the Viking Lander probes which would land on Mars. Sagan examined possible landing sites for Viking along with Mike Carr and Hal Masursky.

From Cosmos and his frequent appearances on The Tonight Show Starring Johnny Carson, Sagan became associated with the catchphrase "billions and billions". Sagan stated that he never actually used the phrase in the Cosmos series.^[35] The closest that he ever came was in the book Cosmos, where he talked of "billions upon billions":^[36]

A galaxy is composed of gas and dust and stars—billions upon billions of stars.

—Carl Sagan, Cosmos, chapter 1, page 3^[37]

However, his 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" in viewers' minds),^[35] made him a favorite target of comic performers, including Johnny Carson,^[38] 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 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.^[35]

Similarly he is also known for expressing wonderment at the vastness of space and time, as in his phrase "The total number of stars in the Universe is larger than all the grains of sand on all the beaches of the planet Earth."

Sagan units[link]

As a humorous tribute to him, a sagan has been defined as a unit of measurement equal to at least four billion, since the smallest number that may be described as billions and billions must be two billion plus two billion.^[39][40]

Social concerns[link]

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 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 cataclysm and eventually becoming a spacefaring species. Sagan's deep concern regarding the potential destruction of 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 from the Air Force Scientific Advisory Board and voluntarily surrendered his top secret clearance in protest over the Vietnam War.^[41] 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.

In March 1983, Reagan announced the Strategic Defense Initiative—a multi-billion dollar project to develop a comprehensive defense against attack by 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 than for an enemy to defeat through 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.

When Soviet leader Mikhail Gorbachev declared a unilateral moratorium on the testing of nuclear weapons, which would begin on August 6, 1985—the 40th anniversary of the atomic bombing of Hiroshima—the Reagan administration dismissed the dramatic move as nothing more than propaganda, and refused to follow suit. In response, US anti-nuclear and peace activists staged a series of protest actions at the Nevada Test Site, beginning on Easter Sunday in 1986 and continuing through 1987. Hundreds of people were arrested, including Sagan, who was arrested on two separate occasions as he climbed over a chain-link fence at the test site.^[42]

Personal life and beliefs[link]

Sagan was married three times—in 1957, to biologist Lynn Margulis, mother of Dorion Sagan and Jeremy Sagan; in 1968, to artist Linda Salzman, mother of Nick Sagan; and in 1981, to author Ann Druyan, mother of Alexandra Rachel (Sasha) Sagan and Samuel Democritus Sagan. His marriage to Druyan continued until his death in 1996.

Isaac Asimov described Sagan as one of only two people he ever met whose intellect surpassed his own. The other, he claimed, was the computer scientist and artificial intelligence expert Marvin Minsky.^[43]

Sagan wrote frequently about religion and the relationship between religion and science, expressing his skepticism about the conventional conceptualization of God as a sapient being. For example:

"Some people think God is an outsized, light-skinned male with a long white beard, sitting on a throne somewhere up there in the sky, busily tallying the fall of every sparrow. Others—for example Baruch Spinoza and Albert Einstein—considered God to be essentially the sum total of the physical laws which describe the universe. I do not know of any compelling evidence for anthropomorphic patriarchs controlling human destiny from some hidden celestial vantage point, but it would be madness to deny the existence of physical laws."^[44]

In another description of his view of God, Sagan emphatically writes:

"The idea that God is an oversized white male with a flowing beard who sits in the sky and tallies the fall of every sparrow is ludicrous. But if by God one means the set of physical laws that govern the universe, then clearly there is such a God. This God is emotionally unsatisfying... it does not make much sense to pray to the law of gravity."^[45]

On atheism, Sagan commented in 1981:

"An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed".^[46]

In reply to a question in 1996 about his religious beliefs, Sagan answered, "I'm agnostic."^[47] Sagan's views on religion have been interpreted as a form of pantheism comparable to Einstein's belief in Spinoza's God.^[48] Sagan maintained that the idea of a creator of the universe was difficult to prove or disprove and that the only conceivable scientific discovery that could challenge it would be an infinitely old universe.^[49] According to his last wife, Ann Druyan, he was not a believer:

When my husband died, because he was so famous and known for not being a believer, many people would come up to me—it still sometimes happens—and ask me if Carl changed at the end and converted to a belief in an afterlife. They also frequently ask me if I think I will see him again. Carl faced his death with unflagging courage and never sought refuge in illusions. The tragedy was that we knew we would never see each other again. I don't ever expect to be reunited with Carl.^[50]

In 2006, Ann Druyan edited Sagan's 1985 Glasgow Gifford Lectures in Natural Theology into a book, The Varieties of Scientific Experience: A Personal View of the Search for God, in which he elaborates on his views of divinity in the natural world.

Carl Sagan (center) speaks with CDC employees in 1988.

Sagan is also widely regarded as a freethinker or skeptic; one of his most famous quotations, in Cosmos, was, "Extraordinary claims require extraordinary evidence"^[51] (called the "Sagan Standard" by some^[52]). This was based on a nearly identical statement by fellow founder of the Committee for the Scientific Investigation of Claims of the Paranormal, Marcello Truzzi, "An extraordinary claim requires extraordinary proof."^[53][54] This idea originated with Pierre-Simon Laplace (1749–1827), a French mathematician and astronomer who said, "The weight of evidence for an extraordinary claim must be proportioned to its strangeness."^[55]

Late in his life, Sagan's books elaborated on his skeptical, naturalistic view of the world. In The Demon-Haunted World: Science as a Candle in the Dark, he presented tools for testing arguments and detecting fallacious or fraudulent ones, essentially advocating wide use of critical thinking and the scientific method. The compilation Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, published in 1997 after Sagan's death, contains essays written by Sagan, such as his views on abortion, and his widow Ann Druyan's account of his death as a skeptic, agnostic, and freethinker.

Sagan warned against humans' tendency towards anthropocentrism. He was the faculty adviser for the Cornell Students for the Ethical Treatment of Animals. In the Cosmos chapter "Blues For a Red Planet", Sagan wrote, "If there is life on Mars, I believe we should do nothing with Mars. Mars then belongs to the Martians, even if the Martians are only microbes."^[56]

Sagan was a user and advocate of marijuana. Under the pseudonym "Mr. X", he contributed an essay about smoking cannabis to the 1971 book Marihuana Reconsidered.^[57][58] The essay explained that marijuana use had helped to inspire some of Sagan's works and enhance sensual and intellectual experiences. After Sagan's death, his friend Lester Grinspoon disclosed this information to Sagan's biographer, Keay Davidson. The publishing of the biography, Carl Sagan: A Life, in 1999 brought media attention to this aspect of Sagan's life.^[59][60][61] Not long after his death, widow Ann Druyan had gone on to preside over the board of directors of NORML, a foundation dedicated to reforming cannabis laws.^[62]

In 1994, engineers at 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.^[4] 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 "Butt-Head Astronomer".^[63][64] Sagan then sued Apple for libel, a form of defamation, in federal court. The court granted Apple's motion to dismiss Sagan's claims and opined in dicta that a reader aware of the context would understand Apple was "clearly attempting to retaliate in a humorous and satirical way", and that "It strains reason to conclude that Defendant was attempting to criticize Plaintiff's reputation or competency as an astronomer. One does not seriously attack the expertise of a scientist using the undefined phrase 'butt-head'."^[63][65] Sagan then sued for Apple's original use of his name and likeness, but again lost.^[66] Sagan appealed the ruling.^[66] In November 1995, 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."^[67]

Sagan briefly served as an adviser on Stanley Kubrick's film 2001: A Space Odyssey.^[6] Sagan proposed that the film would suggest, rather than depict, extraterrestrial superintelligence.^[68]

Sagan and UFOs[link]

Sagan had some interest in UFO reports from at least August 3, 1952 when he wrote a letter to U.S. Secretary of State Dean Acheson to ask how the U.S. would respond if flying saucers turned out to be extraterrestrial.^[69] He later had several conversations on the subject in 1964 with Jacques Vallee.^[70] Though quite skeptical of any extraordinary answer to the UFO question, Sagan thought scientists should study the phenomenon, at least because there was widespread public interest in UFO reports.

Stuart Appelle notes that Sagan "wrote frequently on what he perceived as the logical and empirical fallacies regarding UFOs and the abduction experience. Sagan rejected an extraterrestrial explanation for the phenomenon but felt there were both empirical and pedagogical benefits for examining UFO reports and that the subject was, therefore, a legitimate topic of study."^[71]

In 1966, Sagan was a member of the Ad Hoc Committee to Review Project Blue Book, the U.S. Air Force's UFO investigation project. The committee concluded Blue Book had been lacking as a scientific study, and recommended a university-based project to give the UFO phenomenon closer scientific scrutiny. The result was the Condon Committee (1966–1968), led by physicist Edward Condon, and in their final report they formally concluded that UFOs, regardless of what any of them actually were, did not behave in a manner consistent with a threat to national security.

Ron Westrum writes that "The high point of Sagan's treatment of the UFO question was the AAAS's symposium in 1969. A wide range of educated opinions on the subject were offered by participants, including not only proponents such as James McDonald and J. Allen Hynek but also skeptics like astronomers William Hartmann and Donald Menzel. The roster of speakers was balanced, and it is to Sagan's credit that this event was presented in spite of pressure from Edward Condon".^[70] With physicist Thornton Page, Sagan edited the lectures and discussions given at the symposium; these were published in 1972 as UFOs: A Scientific Debate. Some of Sagan's many books examine UFOs (as did one episode of Cosmos) and he claimed a religious undercurrent to the phenomenon.

Sagan again revealed his views on interstellar travel in his 1980 Cosmos series. In one of his last written works, Sagan argued that the chances of extraterrestrial spacecraft visiting Earth are vanishingly small. However, Sagan did think it plausible that Cold War concerns contributed to governments misleading their citizens about UFOs, and that "some UFO reports and analyses, and perhaps voluminous files, have been made inaccessible to the public which pays the bills ... It's time for the files to be declassified and made generally available." He cautioned against jumping to conclusions about suppressed UFO data and stressed that there was no strong evidence that aliens were visiting the Earth either in the past or present.^[72]

Death[link]

Stone dedicated to Carl Sagan in the Celebrity Path of the Brooklyn Botanic Garden

After a long and difficult fight with myelodysplasia, which included three bone marrow transplants, Sagan died of pneumonia at the age of 62 at the Fred Hutchinson Cancer Research Center in Seattle, Washington, on December 20, 1996.^[73] He was buried at Lakeview Cemetery in Ithaca, New York.^[74]

Posthumous recognition[link]

The 1997 movie Contact, based on Sagan's novel of the same name and finished after his death, ends with the dedication "For Carl".

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.^[75]

The landing site of the unmanned Mars Pathfinder spacecraft was renamed the Carl Sagan Memorial Station on July 5, 1997. Asteroid 2709 Sagan is named in his honor.

Sagan's son, Nick Sagan, wrote several episodes in the Star Trek franchise. In an episode of Star Trek: Enterprise entitled "Terra Prime", a quick shot is shown of the relic rover Sojourner, part of the Mars Pathfinder mission, placed by a historical marker at Carl Sagan Memorial Station on the Martian surface. The marker displays a quote from Sagan: "Whatever the reason you're on Mars, I'm glad you're there, and I wish I was with you." Sagan's student Steve Squyres led the team that landed the Spirit Rover and Opportunity Rover successfully on Mars in 2004.

On November 9, 2001, on what would have been Sagan's 67th birthday, the NASA Ames Research Center dedicated the site for the Carl Sagan Center for the Study of Life in the Cosmos. "Carl was an incredible visionary, and now his legacy can be preserved and advanced by a 21st century research and education laboratory committed to enhancing our understanding of life in the universe and furthering the cause of space exploration for all time", said NASA Administrator Daniel Goldin. Ann Druyan was at the Center as it opened its doors on October 22, 2006.

Sagan has at least three awards named in his honor:

• The Carl Sagan Memorial Award presented jointly since 1997 by the American Astronomical Society (AAS) and the Planetary Society,
• The Carl Sagan Medal for Excellence in Public Communication in Planetary Science presented since 1998 by the American Astronomical Society's Division for Planetary Sciences (AAS/DPS) for outstanding communication by an active planetary scientist to the general public—Carl Sagan was one of the original organizing committee members of the DPS, and
• The Carl Sagan Award for Public Understanding of Science presented by the Council of Scientific Society Presidents (CSSP)—Sagan was the first recipient of the CSSP award in 1993.^[76]

In 2006, the Carl Sagan Medal was awarded to astrobiologist and author David Grinspoon, the son of Sagan's friend Lester Grinspoon.

On December 20, 2006, the tenth anniversary of Sagan's death, a blogger, Joel Schlosberg, organized a Carl Sagan "blog-a-thon" to commemorate Sagan's death, and the idea was supported by Nick Sagan.^[77] Many members of the blogging community participated.

August 2007 the Independent Investigative Group IIG awarded Sagan posthumously a Lifetime Achievement Award. This honor has also been awarded to Harry Houdini and James Randi.^[78]

Beginning in 2009, a musical project known as Symphony of Science sampled several excerpts of Sagan from his series Cosmos and remixed them to electronic music. To date, the videos have received over twenty-million views worldwide on the popular user generated website Youtube, and have exposed a new generation to the interconnected grandeur of the universe as Sagan described them in his documentary series.^[79]

Awards and honors[link]

NASA Distinguished Public Service Medal

• Annual Award for Television Excellence—1981—Ohio State University—PBS series Cosmos
• Apollo Achievement Award—National Aeronautics and Space Administration
• NASA Distinguished Public Service Medal—National Aeronautics and Space Administration (twice)
• Emmy—Outstanding Individual Achievement—1981—PBS series Cosmos
• Emmy—Outstanding Informational Series—1981—PBS series Cosmos
• Exceptional Scientific Achievement Medal—National Aeronautics and Space Administration
• Helen Caldicott Leadership Award – Awarded by Women's Action for Nuclear Disarmament
• Hugo Award—1981—Cosmos
• Humanist of the Year—1981—Awarded by the American Humanist Association
• In Praise of Reason Award—1987—Committee for the Scientific Investigation of Claims of the Paranormal
• Isaac Asimov Award—1994—Committee for the Scientific Investigation of Claims of the Paranormal
• John F. Kennedy Astronautics Award—American Astronautical Society
• John W. Campbell Memorial Award—1974—The Cosmic Connection: An Extraterrestrial Perspective
• Joseph Priestley Award—"For distinguished contributions to the welfare of mankind"
• Klumpke-Roberts Award of the Astronomical Society of the Pacific—1974
• Konstantin Tsiolkovsky Medal—Awarded by the Soviet Cosmonauts Federation
• Locus Award 1986—Contact
• Lowell Thomas Award—Explorers Club—75th Anniversary
• Masursky Award—American Astronomical Society
• Miller Research Fellowship—Miller Institute (1960–1962)
• Oersted Medal—1990—American Association of Physics Teachers
• Peabody Award—1980—PBS series Cosmos
• Prix Galbert—The international prize of Astronautics
• Public Welfare Medal—1994—National Academy of Sciences^[80]
• Pulitzer Prize for General Non-Fiction—1978—The Dragons of Eden
• SF Chronicle Award—1998—Contact
• Named the "99th Greatest American" on the June 5, 2005, Greatest American show on the Discovery Channel
• Named an honorary member of the Demosthenian Literary Society on November 10, 2011
• 2009 New Jersey Hall of Fame inductee.^[81]

Publications[link]

• Planets (LIFE Science Library), Sagan, Carl, Jonathan Norton Leonard and editors of Life, Time, Inc., 1966
• Intelligent Life in the Universe, I.S. Shklovskii coauthor, Random House, 1966, ISBN 1-892803-02-X, 509 pgs (note: republished in 1998 by Emerson-Adams Press)
• UFOs: A Scientific Debate, Thornton Page coauthor, Cornell University Press, 1972, 310 pgs
• Communication with Extraterrestrial Intelligence. MIT Press, 1973, 428 pgs
• Mars and the Mind of Man, Sagan, Carl, et al., Harper & Row, 1973, 143 pgs
• The Cosmic Connection: An Extraterrestrial Perspective, Jerome Agel coauthor, Anchor Press, 1973, ISBN 0-521-78303-8, 301 pgs
• Other Worlds. Bantam Books, 1975
• Murmurs of Earth: The Voyager Interstellar Record, Sagan, Carl, et al., Random House, ISBN 0-394-41047-5, 1978
• The Dragons of Eden: Speculations on the Evolution of Human Intelligence. Ballantine Books, 1978, ISBN 0-345-34629-7, 288 pgs
• Broca's Brain: Reflections on the Romance of Science. Ballantine Books, 1979, ISBN 0-345-33689-5, 416 pgs
• Cosmos. Random House, 1980. Random House New Edition, May 7, 2002, ISBN 0-375-50832-5, 384 pgs
• The Cold and the Dark: The World after Nuclear War, Sagan, Carl et al., Sidgwick & Jackson, 1985
• Comet, Ann Druyan coauthor, Ballantine Books, 1985, ISBN 0-345-41222-2, 496 pgs
• Contact. Simon and Schuster, 1985; Reissued August 1997 by Doubleday Books, ISBN 1-56865-424-3, 352 pgs
• A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, Richard Turco coauthor, Random House, 1990, ISBN 0-394-58307-8, 499 pgs
• Shadows of Forgotten Ancestors: A Search for Who We Are, Ann Druyan coauthor, Ballantine Books, October 1993, ISBN 0-345-38472-5, 528 pgs
• Pale Blue Dot: A Vision of the Human Future in Space. Random House, November 1994, ISBN 0-679-43841-6, 429 pgs
• The Demon-Haunted World: Science as a Candle in the Dark. Ballantine Books, March 1996, ISBN 0-345-40946-9, 480 pgs (note: the book was first published and copyrighted in 1995 with an errata slip inserted)
• Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium, Ann Druyan coauthor, Ballantine Books, June 1997, ISBN 0-345-37918-7, 320 pgs
• The Varieties of Scientific Experience: A Personal View of the Search for God, Carl Sagan (writer) & Ann Druyan (editor), 1985 Gifford lectures, Penguin Press HC, November 2006, ISBN 1-59420-107-2, 304 pgs

References[link]

Further reading[link]

• Davidson, Keay (1999). Carl Sagan: A Life. New York: John Wiley & Sons. pp. 33–41. ISBN 0-471-25286-7. 
• Head, Tom (ed.) (2005). Conversations with Carl Sagan. Jackson, Mississippi: University Press of Mississippi. ISBN 1-57806-736-7. 
• Poundstone, William (1999). Carl Sagan: A Life in the Cosmos. New York: Henry Holt & Company. ISBN 0-8050-5766-8. 
• Morrison, David (2006). "Carl Sagan: The People's Astronomer" (PDF). AmeriQuests 3 (2). http://ejournals.library.vanderbilt.edu/ameriquests/include/getdoc.php?id=402&article=93&mode=pdf. 
• Achenbach, Joel (1999). Captured by Aliens: the search for life and truth in a very large universe. New York: Simon & Schuster. ISBN 0-684-84856-2. [Includes detailed account of Sagan's role in the search for extraterrestrial life. Lay summary]. 

External links[link]

Find more about Carl Sagan on Wikipedia's sister projects:
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	Quotations from Wikiquote
	Source texts from Wikisource

• The Carl Sagan Portal
• Video of skit from The Tonight Show Starring Johnny Carson mentioning "billions and billions"
• BBC Radio program "Great Lives" on Carl Sagan's life
• A Man whose time Has come—Interview with Carl Sagan by Ian Ridpath, New Scientist 1974 July 4
• Carl Sagan at the Internet Movie Database
• Works by or about Carl Sagan in libraries (WorldCat catalog)
• Carl Sagan Prize for Science Popularization
• Sagan Medal for Excellence in Public Communication in Planetary Science, presented by the American Astronomical Society's Division for Planetary Sciences (AAS/DPS)
• Carl Sagan Center for the Study of Life in the Universe, SETI Institute
• Carl Sagan's Life and Legacy as Scientist, Teacher, and Skeptic, Committee for Skeptical Inquiry
• A Tribute to Carl Sagan: Our Place in the Universe, The Skeptics Society