Encyclopedia of Evolution.pdf - Online Reading Center

Sagan, Carl (1934–1996) American Astronomer Carl E.
Sagan was famous as an astronomer who adopted an evolutionary
perspective, and as a popularizer of science, particularly
evolution. His books and media productions served as
the major source of evolutionary science for many thousands
of people.
Born November 9, 1934, Carl Sagan was an undergraduate
and then graduate student at the University of Chicago,
where he earned a doctorate in astronomy and astrophysics
in 1960. He taught at Harvard until 1968, when he moved to
Cornell University, where he quickly advanced to the rank of
full professor in 1971.
Astronomy. Sagan’s evolutionary contributions to astronomy
included:
• Planets other than Earth that might have life. Sagan was
among the first to propose that some moons such as Jupiter’s
Europa and Saturn’s Titan might possess oceans and
thus be suitable for the origin of life. These proposals
were later confirmed by spacecraft. He considered that
planetary systems, such as the chemistry and circulation of
an atmosphere, would not only influence life but be influenced
by life. This interactive view of evolution and environment
(see Gaia hypothesis) was more fully developed
by chemist James Lovelock, and by Sagan’s first wife, who
is one of the most significant modern evolutionary biologists
(see Margulis, Lynn).
• The search for extraterrestrial life. Sagan believed that
intelligent life might be common in the universe, a belief
that has been recently challenged (see essay, “Are Humans
Alone in the Universe?”). He designed a plaque that would
be able to communicate information about humans to
intelligent beings regardless of their language. This plaque
was included with a Voyager spacecraft that eventually
left the solar system. Sagan also was a major proponent of
the use of radio telescopes to listen for nonrandom signals
S
from outer space (SETI, or the Search for Extraterrestrial
Intelligence).
Popularization of science. Sagan’s contributions to the
popularization of evolutionary science included Cosmos, a
highly acclaimed 13-part PBS series aired in 1980, which presented
not only extraterrestrial evolution but also the story
of evolution on Earth. He wrote popular books about evolution,
including The Dragons of Eden and Broca’s Brain. His
novel Contact, about humans making contact with an extraterrestrial
intelligence, was a best seller and was adapted into
a prizewinning movie in 1997. Sagan frequently appeared on
The Tonight Show and became associated with the distinctively
delivered phrase “billions and billions,” referring to
the vast number of galaxies in the universe, and which was
eventually used as a book title. Sagan also considered many
traditional religious beliefs to be dangerous to the intellectual
development of individuals and nations. In contrast to frozen
religious dogma, science corrects itself, as he explained in The
Demon-Haunted World, in which he presented some of his
own mistakes as an example of how scientists change their
minds when new evidence shows them to be in error (see scientific
method).
Environmental issues. Sagan’s intense interest in environmental
issues stemmed from his study of astronomy. He
believed that intelligent life may originate frequently in the
universe, but the Fermi Paradox (based upon an offhand
statement by physicist Enrico Fermi) indicated that if intelligence
was common in the universe, humans should have
already been contacted by these other intelligent creatures. To
Sagan, this indicated a strong likelihood that advanced civilizations
tend to destroy themselves before they have a chance
to develop space travel or have time to send and receive
communications over the vast universal distances. Among
the environmental threats that Sagan thought might destroy
humankind were the following: