A message outward

Symbols sent into space

Drawings meant for a reader who has not been born here.

Drawings meant for a reader who has not been born here. The Pioneer plaque, 1972 and 1973, is a metal card with a man, a woman, the solar system, and a map of fourteen pulsars. The Voyager record cover, 1977, tells a later reader how to play the disc, and it uses the same pulsar map and the same hydrogen clock. The Arecibo message, sent on 16 November 1974, is 1,679 bits, the product of two primes, aimed at a cluster of stars. The hydrogen line is the unit underneath those drawings: 21 centimetres, the hyperfine flip of neutral hydrogen. Binary is the writing. Leibniz published a binary arithmetic in 1703. The plaques use it because it is a counting that does not depend on a human alphabet. The Wow! signal is the odd member. It was not sent. On 15 August 1977 a telescope in Ohio recorded a strong narrowband spike near the hydrogen frequency, and Jerry Ehman wrote “Wow!” in the margin. It is filed here because it is the best-known mark of a possible reply, and because nobody decoded it. A picture we transmit and a spike we receive are not the same kind of sentence. The line holds both so the difference stays visible.

Start here. Pioneer plaque. The Pioneer plaque is the first drawing in this set that was bolted to a machine and thrown outward.

1. 1
   Pioneer plaqueA metal card bolted to a machine, written for a reader who is not from here.
2. 2
   Voyager Golden Record coverInstructions for a disc: how to play it, and where the player lives.
3. 3
   Arecibo message1,679 bits, sent once, toward a cluster of stars.
4. 4
   Hydrogen lineA spin-flip of the smallest atom, used as a ruler for strangers.
5. 5
   BinaryTwo digits. Every later machine script is a reader of them.
6. 6
   Wow! signalA strong narrowband spike, circled in red ink, and never repeated.