
''Pale Blue Dot: A Vision of the Human Future in Space'' is a 1994 book by the astronomer
Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 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 e ...
. It is the sequel to Sagan's 1980 book ''
Cosmos
The cosmos (, ; ) is an alternative name for the universe or its nature or order. Usage of the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity.
The cosmos is studied in cosmologya broad discipline covering ...
'' and was inspired by the famous 1990 ''
Pale Blue Dot'' photograph, for which Sagan provides a poignant description. In the book, Sagan mixes philosophy about the human place in the universe with a description of the current knowledge about the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. He also details a human vision for the future.
In 2023, the audiobook of ''Pale Blue Dot'', read by Sagan, was selected by the
Library of Congress
The Library of Congress (LOC) is a research library in Washington, D.C., serving as the library and research service for the United States Congress and the ''de facto'' national library of the United States. It also administers Copyright law o ...
for preservation in the United States
National Recording Registry
The National Recording Registry is a list of sound recordings that "are culturally, historically, or aesthetically significant, and inform or reflect life in the United States." The registry was established by the National Recording Preservation ...
as being "culturally, historically, or aesthetically significant."
Summary
The first part of the book examines the claims made throughout history that Earth and the
human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
species are unique. Sagan proposes two reasons for the persistence of the idea of a
geocentric
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, an ...
, or Earth-centered universe: human pride in our existence, and the threat of torturing those who dissented from it, particularly during the time of the
Roman Inquisition
The Roman Inquisition, formally , was a system of partisan tribunals developed by the Holy See of the Catholic Church, during the second half of the 16th century, responsible for prosecuting individuals accused of a wide array of crimes according ...
. However, he also admits that the scientific tools to prove the
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
orbited the
Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
were (until the last few hundred years) not accurate enough to measure effects such as
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
, making it difficult for astronomers to prove that the geocentric theory was false.

After saying that we have gained humility from understanding that we are not literally the center of the universe, Sagan embarks on an exploration of the entire
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. He begins with an account of the
Voyager program
The Voyager program is an American scientific program that employs two interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter ...
, in which he was a participating scientist. He describes the difficulty of working with the low light levels at distant planets, and the mechanical and computer problems which beset the twin spacecraft as they aged, and which could not always be diagnosed and fixed remotely. Sagan then examines each one of the major planets, as well as some of the moons—including
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
,
Triton, and
Miranda—focusing on whether life is possible at the frontiers of the Solar System.
Sagan argues that studying other
planet
A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
s provides context for understanding the Earth—and protecting humanity's only home planet from environmental catastrophe. He believes that
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's decision to cut back exploration of the
Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
after the
Apollo program
The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...
was a short-sighted decision, despite its expense and declining popularity among the American public. Sagan says future exploration of space should focus on ways to protect Earth and to extend human habitation beyond it. The book was published the same year
comet Shoemaker-Levy 9 crashed into
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, an event Sagan uses to highlight the danger Earth faces from the occasional
asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
or
comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
large enough to cause substantial damage if it were to hit Earth. He says we need the political will to track large extraterrestrial objects, or we risk losing everything. Sagan argues that in order to save the human race,
space colonization
Space colonization (or extraterrestrial colonization) is the human settlement, settlement or colonization of outer space and astronomical bodies. The concept in its broad sense has been applied to any permanent human presence in space, such ...
and
terraforming
Terraforming or terraformation ("Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to mak ...
should be utilized.
Later in the book, Sagan's wife,
Ann Druyan
Ann Druyan ( ; born June 13, 1949) is an American documentary producer and director specializing in the communication of science. She co-wrote the 1980 PBS documentary series ''Cosmos'', hosted by Carl Sagan, whom she married in 1981. She i ...
, challenges readers to pick one of the other planetary dots photographed and featured in the book, and imagine that there are inhabitants on that world who believe that the universe was created solely for themselves. She shared Sagan's belief that humans are not as important as they think they are.
The first edition of the book includes an extensive list of illustrations and photographs, much of it taken from public archives of information released by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
.
See also
*
Anthropocentrism
Anthropocentrism ( ) is the belief that human beings are the central or most important entity on the planet. The term can be used interchangeably with humanocentrism, and some refer to the concept as human supremacy or human exceptionalism. From a ...
* ''
Earthrise
''Earthrise'' is a photograph of Earth and part of the Moon's surface that was taken from lunar orbit by astronaut William Anders on December 24, 1968, during the Apollo 8 mission. Nature photographer Galen Rowell described it as "the most in ...
'', 1968
Apollo 8
Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave Sphere of influence (astrodynamics), Earth's gravitational sphere of influence, and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times ...
photograph
* ''
The Blue Marble
''The Blue Marble'' is a photograph of Earth taken on December 7, 1972, by either Ronald Evans (astronaut), Ron Evans or Harrison Schmitt aboard the Apollo 17 spacecraft on its way to the Moon. Viewed from around from Earth's surface, a crop ...
'', 1972
Apollo 17
Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, ...
photograph
*
''Wanderers'' (2014 film)
References
*
External links
Sagan's rationale for human spaceflightArticle about Carl Sagan and ''Pale Blue Dot''
Short audio recording of Carl Sagan describing the primary concept of his book ''The Pale Blue Dot'' at the United States Library of Congress Seth MacFarlane Collection of the Carl Sagan and Ann Druyan Archiveby the ''Cassini'' spacecraft on September 15, 2006
More information about photo.''We Are Here: The Pale Blue Dot''.A short, fan-made film on ''The Pale Blue Dot'', released a decade after Sagan's death. The posthumous narration is from Sagan himself, taken from one version of the audiobook version of ''Pale Blue Dot''.
A partial video tour of the Sagan Planet Walk monument in Ithaca, NY
{{Carl Sagan
1994 non-fiction books
American non-fiction books
Astronomy books
Big History
English-language non-fiction books
Global civilization
Random House books
Space colonization literature
Works about the theory of history
Works by Carl Sagan
United States National Recording Registry recordings