1974

1974 is the year the book identifies with SETI’s Arecibo message, a deliberately structured radio transmission that tried to make Earth and its inhabitants intelligible across the gulf between civilizations. The episode supplies a precedent for the later plan to communicate with the Yrr through mathematics, while also raising the danger and limits of broadcasting information into the unknown.

The Arecibo transmission

In 1974, SETI sent a powerful radio signal from Earth toward a globular cluster in the constellation of Hercules. Its 1,679 characters were encoded as binary pulses, a sequence of ones and zeros. The number itself offered a clue to the message’s organization: 1,679 is the product of the prime numbers 23 and 73, so the pulses could be arranged as 73 columns of 23 characters. Rendered as alternating black and white blocks, the sequence formed a pattern that a recipient with the relevant mathematical understanding could begin to interpret.

What the message conveyed

The design moved from basic numerical information toward a portrait of terrestrial life. Its upper lines represented the numbers one through ten and explained the decimal system. It then gave the atomic numbers of water, carbon, oxygen, nitrogen, and phosphorus, followed by information about Earth’s biochemistry, including DNA bases and sugars and the structure of the double helix. An image of the human form was linked to the DNA representation, offering a route to infer something about evolution on Earth.

The message also addressed the problem of communicating measurements across radically different frames of reference. Rather than rely on human units of size, it used the signal’s wavelength to indicate average human height. A diagram of the solar system and information about the appearance, dimensions, and design of the Arecibo Observatory completed the transmission, identifying both the setting of its senders and the instrument from which it had been sent.

Precedent and risk

The Arecibo message is presented as an ambitious attempt to make human knowledge legible, but its disclosure of Earth and humanity also provoked concern that such a transmission might invite danger. The response in the discussion is that Earth had already been broadcasting radio waves for decades: ordinary radio traffic, including intelligence-agency communications, was escaping into space and could reveal the presence of a technological civilization even without being decoded. The deliberate message therefore did not create the possibility of detection from nothing; it made that possibility explicit and organized.

Its timescale underscored the distance between sending a signal and establishing communication. The Arecibo transmission was expected to take 26,000 years to reach its destination, with a reply taking another 26,000 years. Against that almost unimaginable delay, the proposed underwater communication with the Yrr was presented as faster. The plan would proceed in stages, beginning with two mathematical problems intended to establish the Yrr’s existence and test whether dialogue could be initiated. In this way, 1974 functions not as a successful encounter but as a technical and conceptual precedent for a more immediate attempt at contact.