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moment in our galaxy alone 50 million different civilisations which are either trying to get in touch with us or waiting for a sign from other planets. The terms of the Green Bank Formula take into account all the aspects in question, but in addition the scientists allotted two values to each term; a normal value admissible according to our present state of N=R, fonefififeL ne = the average number of planets which orbit the ecosphere of their sun and so have adequate premises for the development of life by human standards. civilisation. L = the life-span of a civilisation, for only civilisations that were very long lasting could encounter each other given the vast distances in the universe. N = 40. knowledge and an absolute minimum value. In this formula: R+ = the average annual number of new stars that are like our sun. fP = the number of stars with possible living beings. fi = the number of planets favoured in this way on which life has actually developed. fi = the number of planets which are populated by intelligences with their own ability to act during the lifetime of their sun. fc = the number of planets inhabited by intelligences that already have a developed technical If we take the lowest possible figures for all terms in this formula, we get: But if we take the admissible maximum value, we get: N = 50,000,000. In other words, in the most unfavourable case the fantastic Green Bank Formula calculates that there are forty groups of intelligences in our Milky Way who are seeking contact with other intelligences. The most audacious possibility gives 50 million unknown intelligences who are waiting for a sign from the cosmos.