I. This November
Somewhere above the plane in which the planets orbit, moving away from the sun at some 17
kilometres a second, a machine older than the internet is closing in on no ordinary milestone.
On November 18, Voyager I will be one light-day away from earth.
In 1965, a graduate student in the U.S. named Gary Flandro noticed that around the late 1970s,
Jupiter, Saturn, Uranus, and Neptune would lie on a single line — something that happens only
around every 175 years. So, a spacecraft launched at the right moment could use each planet’s
gravity to arc towards the next, compressing a 30-year crawl to Neptune into a single decade.
NASA dreamed big at first, but as the budget priorities changed, the plan shrank to two probes
aimed only at Jupiter and Saturn. These were the Voyagers.
Scientists and engineers built two nearly identical spacecraft, and launched them 16 days apart:
Voyager II first on August 20, 1977, then Voyager I. As it happened, Voyager I would take a faster
path that let it overtake its sibling and reach Jupiter first. And from here the two machines
lived very different lives.
Voyager I is built like a decagon-shaped drum to pack the electronics and the propellant tank
into a light frame. Sixteen thrusters keep a 3.7-metre dish antenna pointing at earth. Three
nuclear generators sit at the end of a long boom to keep their radioactivity from corrupting the
instruments.
The Voyagers couldn’t afford a gram of decoration. They’re purely functional objects.
II. The Golden Record
Voyager I and Voyager II each carry a golden phonograph record bolted to their exteriors.
The idea was that the mission ought to carry some kind of message explaining ourselves and our planet to any interstellar intelligence it may encounter that shared none of our biology, language, or history.
Project manager John Casani handed the problem of designing a message to Carl Sagan, who invited
the radio astronomer Frank Drake. Their official budget was $1,500 for six weeks — an absurd sum
for a message meant to represent an entire species, and in practice it took most of the following
year to compose.
They assembled 116 photographs of human anatomy, cities, farms, a mother nursing a child, the
structure of DNA, a 12-minute audio collage of surf, thunder, birdsong, humpback whales, and a
baby’s first cry; greetings in more than 50 languages; and 90 minutes of music from Bach to a
Navajo night chant to Chuck Berry’s ‘Johnny B. Goode’.
At Sagan’s request, the documentary maker Ann Druyan spent an hour in a lab with electrodes on
her scalp, thinking her way through the history of earth. Two days after she and Sagan had
privately agreed to marry, she thought of what it felt like to fall in love. That hour of brain
activity was encoded onto the record as sound as well.
Whimsical though it sounds, the record’s design posed a significant challenge: how do you write
instructions for an alien entity with a different alphabet, units or even senses? So its
designers picked something universal: physics. The playback speed was set by the oscillation of
a hydrogen atom, location marked by a map of pulsars, the cover plated with uranium-238, whose
decay lets a finder calculate exactly how long it has been travelling.
