"The Cosmos is all that is or ever was or ever will be." That's the first line out of the first chapter of the number one best selling book Cosmos, based on the Peabody - and - Emmy - award - winning TV series written by Dr. Carl Sagan. Carl Sagan was the David Duncan Professor of Astronomy and Space Studies and Director of the Laboratory for Planetary Studies at Cornell University. He played a leading role in the Mariner, Viking, and Voyager expeditions to the planets for which he received the NASA Medal for Exceptional Scientific Achievement, the Prix Galabert, the International Astronautics Prize, the NASA Medal for Distinguished Public Service (on two occasions), and the John F. Kennedy Astronautics Award of the American Astronautical Society. Dr. Sagan was the first president of The Planetary Society, a non-profit, tax-exempt membership organization dedicated to the exploration of the solar system and the search for extraterrestrial life. Founded in 1980 by Carl Sagan and Bruce Murray, the Society now has more than 100,000 dues-paying members in the United States, Canada and over 50 other nations.

His scientific research has enhanced our understanding of the greenhouse effect on Venus, dust storms on Mars, the organic clouds of Titan (moon of Saturn), the origin of life, and the search for life elsewhere, for which he is best known for. Dr. Sagan and his colleagues were also engaged in research on Nuclear Winter, the previously unsuspected global climatic catastrophe that may follow a nuclear war.

Carl was born in Brooklyn, New York on November 9, 1934. Growing up as a child Carl looked up to the sky and saw the stars and wondered what they were. He asked other kids and adults and some said: "There lights in the sky kid." He knew that, but what where they? To find the answer he took a trip to his local library and asked the librarian for a book on stars. The librarian brought him a book with pictures of people like Clark Gable, Jean Harlow, and Alan Ladd. He told the woman that this wasn't what he was looking for at all, so she brought him another book, the right book. He breathlessly opened the book and read it until he found the answer. It said that stars were suns but very far away. The Sun was a star but close up.

Imagine taking the Sun and moving it away until it was a twinkle of light like the stars. How far away would it have to be? Back then he didn't have a chance of finding the answer. He was innocent of the notion of angular size and was ignorant of the inverse square law for light propagation. But he could tell that if the stars were suns they had to be very far way - farther than 85th Street, farther away than Manhattan , farther away, probably, than New Jersey. The Cosmos was bigger than he could have possibly imagined.

Later he read another amazing fact. The Earth is a planet and goes around the Sun. There are other planets that also go around the sun. He wondered if the stars in the sky also had planets that have not yet been discovered. He also thought that those planets should have life. Why not? It's ignorant to think that the Earth is the only planet in the universe that could support life. What's so special about the Earth which orbits an ordinary yellow dwarf star? There are billions of other stars just like the sun in the Milky Way and there are billions of other galaxies like our own. Just exactly how many intelligent alien races are there in the Milky Way? I can't give you an exact answer, but I can give an idea of how many there may be if we look at the variables involved in the process of life. To do this we can use Drake's equation. This was developed by Carl Sagan and Frank Drake at Cornell University. It is used to calculate the number (N) of advanced technical civilizations that may exist in the Milky Way at any giving time. For the most part, the variables used in the example calculation below are educational guesses, especially the final three. Basically, it's little more that a thought provoking experiment. Play with the variables on your own and see what you come up with.

In this equation, the number of advanced technical civilization N is assumed by multiplying the following variables:

	N* = 250 billion (number of stars in the Milky Way Galaxy)
	fp = 1/4 (fraction of stars that have planetary systems)
	ne = 2 (number of planets in a given system that are ecologically suitable for life)
	fl = 1/2 (fraction of otherwise suitable planets on which life actually arises)
	fi = 1/10 (fraction of inhabited planets on which an intelligent form of life evolves)
	fc = 1/10 (fraction of planets inhabited by intelligent beings on which a communicative technical civilization develops)
	fL = 1/100 (fraction of a planetary lifetime graced by a technical civilization)

The idea of extraterrestrial intelligence in the cosmos is not a new one. It was touched upon by the Pythagoreans in the 5th century BC and by the Greek atomists Democritus and Epicurus in the 4th century BC. Lucretius, Rome's most distinguished philosopher-poet, who lived from 95-55 B.C., said that:


In the sixteenth century the Italian philosopher, Bruno stated:


So why search for life elsewhere in the Cosmos? Isn't there enough trouble with life right here on Earth? Maybe there is. But the discovery of extraterrestrials has been the dream of the human race since we learned how to write thousands of years ago. We wonder what they look like, what are they made of, how do they think, communicate, how intelligent are they? What else is possible? To put it in Carl Sagan's words: "The search for extraterrestrial intelligence is a search for who we are."


Works Published

• Intelligent Life in the Universe (1966)
• The Cosmic Connection (1973)
• The Dragons of Eden (1977), for which he won the 1978 Pulitzer Prize
• Broca's Brain (1979)
• Cosmos (1980), based on his television series
• Comet (1985)
• Contact (1985), a novel
• Shadows of Forgotten Ancestors (1992)
• Pale Blue Dot (1994)
• The Demon Haunted World (1996)
• Billions and Billions (1997)
• Plus over 600 published scientific papers and popular articles.

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Related Links

• Astronomy Department -- Cornell University
• The Planetary Society
• Contact -- The Movie (based on the novel by Carl Sagan)
• Carl Sagan Productions