SETI, false alarms

Two incidents stand out in the chronicles of SETI which, at the time, suggested that signals might have been detected from an extraterrestrial intelligence. The first was in 1963 when the radio source designated CTA-102 was claimed by Soviet astronomers to be evidence of a highly advanced alien civilization. In 1967, S. Jocelyn Bell (now Bell Burnell) recorded a regular pulsating signal using a radio telescope in Cambridge, England, designed by Anthony Hewish to look for rapid variations in the radio wave emission of quasars. An early theory was that the pulses might be coming from an interstellar beacon and the source was tentatively catalogued as LGM, for "little green men." However, it quickly became clear that this, and other, similar sources which were detected soon after, could be explained naturally in terms of rotating neutron stars, or pulsars.