The Reply to Voyager

At seventeen minutes past three on a Tuesday morning in July, in the depths of the southern winter, Dr. Paulina Rojas was the only person awake in the control building of a small radio observatory in the Atacama Desert, a few kilometers from the great dishes of ALMA. Outside, the air above the plateau was so dry and so still that the Milky Way seemed close enough to brush the antennas. She was halfway through a cup of instant coffee when the software flagged a narrow, unwavering tone at 8.4 gigahertz.

Her first assumption, which was also the one she had been trained to make, was that she was looking at interference: a satellite, a passing aircraft, a faulty cable in her own equipment. By half past four she had ruled out all three. What she could not rule out was the position. The tone was coming from a point in the constellation of Pavo, the Peacock, precisely where Voyager 2, launched in 1977 and now almost twenty light-hours from Earth, was known to be. Its path had carried it so far below the plane of the planets that it could only be seen from the southern hemisphere. That night, by pure chance, her dish was surveying that very patch of sky. Yet the probe's own transmitter, scarcely more powerful than a refrigerator light bulb, could never have produced a signal this strong.

Hardly daring to believe it, she sent the raw data to a colleague in Santiago, who called her back before sunrise, too excited to finish his sentences. Once decoded, the signal turned out to contain an image, and it was one that every space engineer would have recognized at once. It was one of the diagrams engraved on the cover of the Golden Record, the gold-plated disc that had been fixed to the side of each Voyager in case anyone, somewhere, should ever find it. The diagram, which had been designed to explain how the record should be played, had been sent back line for line. Beside it was a single mark that matched nothing on the original.

By noon, an emergency committee had been assembled by video. It included astronomers from Chile, engineers from the laboratory in California that still operated the Voyager mission, a Spanish diplomat from the United Nations and two linguists who had been dragged out of bed in Mexico City. The arguments that followed went on for most of the day. One astronomer pointed out that whoever had sent the image was evidently within reach of a probe built in the age of cassette tapes, so staying silent would protect nobody. The diplomat replied that no single country had the right to speak for the planet, and insisted that nothing be transmitted until the General Assembly had been consulted. Somebody asked, with obvious frustration, which language they would even use, and an engineer observed rather dryly that the record had already answered that question fifty-five times. Paulina, who by then had not slept for thirty hours, said almost nothing.

The committee had still not reached a decision when, at seventeen minutes past three on Wednesday morning, the second transmission arrived. This time it was not an image but sound, and when Paulina played it through the speakers, the room went completely silent. It was a voice, and it said five words that everyone present knew by heart: "Hola y saludos a todos," hello and greetings to everyone, the Spanish greeting from the Golden Record. It was not the recording itself, however. Someone, or something, had learned the words and was saying them back, slowly and carefully, in an accent that neither the Chileans, nor the diplomat from Spain, nor the two exhausted linguists in Mexico City had ever heard on Earth.