Extraterrestrial Civilizations (book)
Encyclopedia
Extraterrestrial Civilizations is a book written by Isaac Asimov
in 1979, wherein the probability of there being intelligent extraterrestrial
civilizations within the Milky Way galaxy is estimated. This estimation is approached by progressively analyzing the requirements for life
to exist.
The term "Earth
-like world" is prominent, in that the assumption is made that any world where life could evolve would have certain similarities to Earth, such as temperature ranges and gravity sufficient for an atmosphere to exist. Asimov begins with the estimated amount of star
s in the galaxy, 300 billion.
This number is then reduced to 280 billion as stars without planetary system
s are discarded, and then furthermore reduced as more factors are taken into consideration. This process culminates in the statement that "the number of planets in our galaxy on which a technological civilization is now in being is roughly 530,000."
Isaac Asimov
Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...
in 1979, wherein the probability of there being intelligent extraterrestrial
Extraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...
civilizations within the Milky Way galaxy is estimated. This estimation is approached by progressively analyzing the requirements for life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
to exist.
The term "Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
-like world" is prominent, in that the assumption is made that any world where life could evolve would have certain similarities to Earth, such as temperature ranges and gravity sufficient for an atmosphere to exist. Asimov begins with the estimated amount of star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s in the galaxy, 300 billion.
This number is then reduced to 280 billion as stars without planetary system
Planetary system
A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets , asteroids, meteoroids, comets, and cosmic dust...
s are discarded, and then furthermore reduced as more factors are taken into consideration. This process culminates in the statement that "the number of planets in our galaxy on which a technological civilization is now in being is roughly 530,000."