I want to start with a red pen. In August of 1977, a volunteer astronomer named Jerry Ehman sat reviewing computer printouts from a radio telescope in Ohio called Big Ear. The telescope had been listening to the sky and printing what it heard as columns of numbers and letters, and most of every page was the quiet hiss of the galaxy. Then Ehman's eye caught a vertical run of six characters, seventy-two seconds of signal at more than thirty times the background of the universe: 6EQUJ5. He circled the sequence in red and wrote one word in the margin. Wow!
The signal never repeated. The day after it reached Ohio, Elvis Presley was found unresponsive at Graceland, and the country turned to a different grief. Four days after that, a Titan rocket stood on a Florida launch pad carrying a machine named Voyager, and bolted to its side was a gold-plated phonograph record.