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Sending Our Own Signals We ourselves are now capable of producing at will various phenomena. ... which could be observed from distant planets....We must, therefore, revise our thinking and incorporate in our theories possible effects of the free will of other living beings. OVA Cteriern 10691 Some of those interested in searching for extraterrestrials have proposed that we initiate contact by sending our own signals, in the hope that another civilization will detect them and respond. Calling attention to ourselves by such signaling has been described as “active SETI,” in contrast to passive listening. The proposed means of sending signals have evolved with technological advance and with the remoteness of the target. Early ideas focused on creating geometric patterns on the Earth’s surface that would be visible to astronomers on other bodies in our solar system. RAL A we Wael Daren ala... al Mathematician Karl Gauss allegedly proposed in 1826 that we signal intelligent beings on the Moon by clearing vast lanes of forest in Siberia to show the Pythagorean theorem by means of areas surrounding a right tri- angle. Austrian astronomer Joseph Von Littrow reportedly suggested in 1840 that we signal Mars by digging long canals in geometric shapes in the Sahara desert, filling them with water and kerosene, and setting them on Gan a4 tee fire at night. Other concepts employed the transmission of light. Gauss recommended that we signal the Moon with an array of 100 mirrors; Charles Cros pro- posed that huge mirrors be used to focus light on Mars or Venus, sending messages by periodic flashes. American astronomer Henry Pickering, who suggested signaling Mars with mirrors during the opposition of 1909, thought that a mirror one-half square mile in area would be dazzlingly conspicuous to Martian observers. As recently as 1941, James Jeans proposed that we flash prime numbers toward Mars.’ 49 —Otto Struve, 1962! Active SETI