It was 37 seconds long and came from outer space. On 15 August 1977 it caused astronomer Jerry Ehman, then of Ohio State University in Columbus, to scrawl "Wow!" on the printout from Big Ear, Ohio States radio telescope in Delaware. And 28 years later no one knows what created the signal. "I am still waiting for a definitive explanation that makes sense," Ehman says.Coming from the direction of Sagittarius, the pulse of radiation was confined to a narrow range of radio frequencies around 1420 megahertz. This frequency is in a part of the radio spectrum in which all transmissions are prohibited by international agreement. Natural sources of radiation, such as the thermal emissions from planets, usually cover a much broader sweep of frequencies. So what caused it?
http://www.newscientist.com/channel/space/mg18524911.600
