IT WAS Jerry Ehman's turn to check on the "Big Ear" radio telescope at Ohio State Radio Observatory on 15 August 1977. The 79-metre dish had been involved in the search for extraterrestrial intelligence since 1973. Its receiver was tuned close to the 1420-megahertz frequency at which the hydrogen atoms of interstellar space broadcast radio waves like miniature radio stations.
The 1970s were the Stone Age for computersthe one at the Ohio State Radio Observatory had a paltry 32K of RAM and a megabyte hard disc. This meant that the fluctuating voltages picked up by the telescope could not be stored electronically but had to be printed out and examined by the SETI volunteers at the observatory every few days. It was this task that fell to Ehman, a professor at Ohio State University, that day in August.
When Ehman worked his way through the reams of paper spewed out ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.