In Human Universe episode 3: Brian Cox explores the ingredients needed for an intelligent civilisation to evolve in the universe – the need for a benign star, for a habitable planet, for life to spontaneously arise on such a planet and the time required for intelligent life to evolve and build a civilisation. Brian weighs the evidence and arrives at his own provocative answer to the puzzle of our apparent solitude.
Human Universe episode 3: Are We Alone?
In 1977 a radio signal was received that bore all the hallmarks of coming from an alien intelligence. To this day, its origin remains unknown.
The Wow! signal was a strong narrowband radio signal received on August 15, 1977, by Ohio State University’s Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin. Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout and wrote the comment Wow! on its side, leading to the event’s widely used name.
The ‘Wow’ signal
The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and man-made sources, but none of them adequately explains the result.[3] The Wow! signal remains the strongest candidate for an alien radio transmission ever detected.
The alphanumeric sequence circled by Ehman, 6EQUJ5, represents the intensity variation of the radio signal over time, measured as unitless signal-to-noise ratio and ranging from 0 to 36, with the noise averaged over the previous few minutes. Each individual character corresponds to a sample of the signal, taken every 12 seconds. A space character on the printout denotes an intensity between 0 and 1; the numbers “1” to “9” denote the correspondingly numbered intensities (from 1 to 9); intensities of 10 and above are indicated by a letter: “A” corresponds to intensities between 10 and 11, “B” to 11 to 12, and so on. The highest measured value was “U” (an intensity between 30 and 31), that is thirty times stronger than normal background noise.
