One of the worries that kept legendary astronomer Carl Sagan up at night was whether aliens would understand us. In the mid-1970s, Sagan led a committee formed by NASA to assemble a collection of images, recorded greetings, and music to represent Earth. The montage was pressed onto golden albums and dispatched across the cosmos on the backs of Voyagers 1 and 2.
In a 1986 story Sagan wrote for Popular Science, he noted that “hypothetical aliens are bound to be very different from us—independently evolved on another world,” which meant they likely wouldn’t be able to decipher the golden discs. But he took assurance from an underappreciated dimension of Voyagers’ message: the designs of the vessels themselves.
“We are tool makers,” Sagan wrote. “This is a fundamental aspect, and perhaps the essence, of being human.” What better way to tell alien civilizations that Earthlings are toolmakers than by sending a living room-sized, aluminum-framed probe clear across the Milky Way.
Although both spacecraft were only designed to swing by Jupiter and Saturn, Voyager 2’s trajectory also hurled it past Uranus and Neptune. Despite numerous mishaps along the way—and because of the elite toolmaker skills of NASA engineers—the probe was in good enough shape to send back close-ups of those distant worlds. In 2012, Voyager 1 became the first interstellar spacecraft, followed soon thereafter by Voyager 2. “Once out of the solar system,” Sagan wrote, “the surfaces of the spacecraft will remain intact for a billion years or more,” so resilient is their design.
Today, the probes are 12–15 billion miles from Earth, still operable (despite experiencing recent communication difficulties), and sailing through the relative calm of interstellar space. They are expected to continue to transmit data back to Earth for another year or so, or until their plutonium batteries quit.
It was early 20th century wireless inventor Guglielmo…
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