The most distant object human beings have ever made is carrying a gramophone record. Voyager 1, launched in September 1977 and now more than twenty billion kilometres from the Sun, has bolted to its flank a twelve-inch disc of gold-plated copper, sealed inside an aluminium cover along with a cartridge and stylus and engraved instructions for playing it at sixteen and two-thirds revolutions per minute. An identical disc rides on its twin, Voyager 2. Between them, the Golden Records are the closest our species has come to a message in a bottle flung into the cosmic ocean — and, in all likelihood, the longest-lived objects we have ever built.
The Voyagers themselves were built to exploit a rare piece of celestial luck: an alignment of the outer planets, occurring roughly once every 175 years, that let a spacecraft slingshot from Jupiter to Saturn and onwards. Voyager 2 actually launched first, on 20 August 1977, with Voyager 1 following on 5 September along a faster route; Voyager 2 went on to become the only spacecraft ever to visit Uranus and Neptune. When NASA decided the probes should carry a message, it turned to the astronomer Carl Sagan, who had already sent engraved plaques out on the Pioneer probes. Sagan assembled a small team — the writer Ann Druyan as creative director, the science journalist Timothy Ferris as producer — and had roughly six months to decide how to compress the Earth onto one disc.
What Earth chose to say
The finished record holds 115 encoded images, spoken greetings in 55 languages — from Akkadian, dead for thousands of years, to Wu Chinese — and a sound-essay of Earth: thunder, surf, crickets, a train, a kiss, a mother soothing her child. The greetings share the disc with the songs of humpback whales, included on the theory that they too were intelligent inhabitants worth hearing from. Then come 90 minutes of music in 27 pieces, with Johann Sebastian Bach appearing three times — more than any other composer — alongside Beethoven's Fifth Symphony, Mozart's Queen of the Night aria, a Javanese gamelan, Peruvian panpipes, a Georgian choir, Blind Willie Johnson's wordless gospel lament Dark Was the Night, Cold Was the Ground, and Chuck Berry's Johnny B. Goode. A story often repeated — resting mainly on Sagan's own telling — says the Beatles were happy for Here Comes the Sun to fly, but the company holding the copyright refused. Saturday Night Live later joked that the first alien reply read simply: "Send more Chuck Berry."
The record's most intimate track is inaudible as sound. Days after Ann Druyan and Carl Sagan fell in love and privately agreed to marry, Druyan had the electrical activity of her brain recorded for an hour while she thought about Earth's history, human violence, and what it is to love someone. The compressed crackle of her nervous system rides on the disc; the two married in 1981.
The map home
The cover doubles as instruction manual and return address. A starburst diagram locates the Sun by its bearings to 14 pulsars, each identified by its spin period written in binary — a signature no natural process would counterfeit. Another diagram uses the fundamental transition of the hydrogen atom as a universal tick of time. And electroplated onto the cover is a spot of uranium-238: with a half-life of about 4.5 billion years, it is a clock from which any finder could date the launch by measuring how much has decayed. Not everyone approved of publishing our address — the radio astronomer Martin Ryle protested that advertising our whereabouts was reckless — but the odds of interception are vanishingly small, and in the emptiness between stars the discs should remain playable for a billion years.
Voyager 1 crossed into interstellar space in 2012, Voyager 2 in 2018, and both have kept whispering data home on transmitters weaker than a fridge lightbulb. Neither is aimed at any star: in roughly 40,000 years Voyager 1 will simply drift within a couple of light-years of a red dwarf called Gliese 445, and keep going. In 1990, at Sagan's urging, Voyager 1 turned its camera back for a final family portrait and caught Earth as a single pale blue pixel suspended in a sunbeam.
Sagan understood that the records were less a letter to aliens than a mirror held up to their senders, and said the launching of this bottle into the cosmic ocean spoke hopefully about life on this planet. Long after the Sun has swollen and the Earth is gone, two small discs of gold and copper will still be out there, carrying Bach and whale song into the dark.
Quiz nuggets
- Voyager 2 launched first, on 20 August 1977; Voyager 1 followed on 5 September and is now the most distant human-made object.
- Each Golden Record is a 12-inch gold-plated copper disc carrying 115 images, greetings in 55 languages and about 90 minutes of music.
- Bach appears three times on the record — more than any other composer — alongside Chuck Berry's Johnny B. Goode.
- The record's cover locates the Sun using a map of 14 pulsars, with an electroplated sample of uranium-238 acting as a radioactive clock.
- Voyager 1 entered interstellar space in 2012; Voyager 2 remains the only spacecraft to have visited Uranus and Neptune.