UFO Timeline

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On the night of 24/25 March 1975, Carl Sagan and Frank Drake used the
During June 1975, Michael Hart’s paper entitled “An Explanation for the Absence of Extraterrestrials on Earth” was published by the Quarterly Journal of the Royal Astronomical Society.

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This incident is Case 94 in Isaac Koi's "Top 100" article, since it was referred to in 30 of the books covered by that article.