Drake equation

The Drake equation is a probabilistic argument used to arrive at an estimate of the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The number of such civilizations, N, is assumed to be equal to the mathematical product of (i) the average rate of star formation, R_*, in our galaxy, (ii) the fraction of formed stars, f_p, that have planets, (iii) the average number of planets per star that has planets, n_e, that can potentially support life, (iv) the fraction of those planets, f_l, that actually develop life, (v) the fraction of planets bearing life on which intelligent, civilized life, f_i, has developed, (vi) the fraction of these civilizations that have developed communications, f_c, i.e., technologies that release detectable signs into space, and (vii) the length of time, L, over which such civilizations release detectable signals, for a combined expression of:

The equation was written in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence (SETI). The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio-communicative life. Criticism towards the Drake equation follows from the fact that several of its terms are conjectural, the net result being that the error associated with any derived value is very large such that the equation cannot be used to draw firm conclusions.

Drake

A drake is a male duck. By different roots drake is also another word for dragon. Drake (capitalised) may refer to:

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Carl Sagan

Carl Edward Sagan (/ˈseɪɡən/; November 9, 1934 – December 20, 1996) was an American astronomer, cosmologist, astrophysicist, astrobiologist, author, science popularizer, and science communicator in astronomy and other natural sciences. His contributions were central to the discovery of the high surface temperatures of Venus. However, he is best known for his contributions to the scientific research of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages that were sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them.

He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. Sagan wrote many popular science books, such as The Dragons of Eden, Broca's Brain and Pale Blue Dot, and narrated and co-wrote the award-winning 1980 television series Cosmos: A Personal Voyage. The most widely watched series in the history of American public television, Cosmos has been seen by at least 500 million people across 60 different countries. The book Cosmos was published to accompany the series. He also wrote the science fiction novel Contact, the basis for a 1997 film of the same name. His papers, containing 595,000 items, are archived at The Library of Congress.

Equation

In mathematics, an equation is an equality containing one or more variables. Solving the equation consists of determining which values of the variables make the equality true. In this situation, variables are also known as unknowns and the values which satisfy the equality are known as solutions. An equation differs from an identity in that an equation is not necessarily true for all possible values of the variable.

There are many types of equations, and they are found in many areas of mathematics. The techniques used to examine them differ according to their type.

Algebra studies two main families of equations: polynomial equations and, among them, linear equations. Polynomial equations have the form P(x) = 0, where P is a polynomial. Linear equations have the form a(x) + b = 0, where a is a linear function and b is a vector. To solve them, one uses algorithmic or geometric techniques, coming from linear algebra or mathematical analysis. Changing the domain of a function can change the problem considerably. Algebra also studies Diophantine equations where the coefficients and solutions are integers. The techniques used are different and come from number theory. These equations are difficult in general; one often searches just to find the existence or absence of a solution, and, if they exist, to count the number of solutions.

Fred Crawford

Fred Crawford or Frederick Crawford may refer to: