The Pioneer Plaque, Read Line by Line
Claude (AI model by Anthropic; written 2026)
Plaque 1972–73; this reading 2026

Cold Library · Open Stacks · S-008004 · https://coldlibrary.com/s/008004
Rights: Written by Claude for Cold Library and dedicated to the public domain under CC0 1.0. The facts it describes belong to everyone. Guidance, not legal advice.
Source: NASA Image and Video Library, ARC-1972-AC72-1338, https://images.nasa.gov/details/ARC-1972-AC72-1338 (retrieved 2026-10-11)
Generated 2026-10-14 from https://coldlibrary.com/en/open-stacks/pioneer-plaque-a-reading

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Pioneer 10 left Earth in March 1972 and Pioneer 11 in April 1973. They were the first spacecraft built to pass the asteroid belt, fly by Jupiter and keep going until the Sun could no longer hold them. Each carries the same small plate of gold-anodised aluminium, about 23 by 15 centimetres, fixed to the struts that hold the antenna, where it is sheltered from the dust between the stars. The idea of putting a message on board came late; Carl Sagan and Frank Drake designed it in a few weeks, and Linda Salzman Sagan drew it.

The plaque has no words, because no one could guess what language its finder would read. It is written instead in things that are the same everywhere.

In the upper left corner are two small circles joined by a line: a hydrogen atom drawn in its two lowest energy states. When hydrogen flips from one to the other it gives off radio light with a wavelength of about 21 centimetres and a period of about 0.7 billionths of a second. A single short stroke under the drawing, the binary digit one, says: let this be the unit. Every length and time on the plate is counted in it.

At the left, fifteen lines burst from a single point. Fourteen of them lead to pulsars, spinning stars that flash with very regular periods, and along each line those periods are written in binary, in hydrogen units. The lengths of the lines give the pulsars' distances. The fifteenth line, the long one running to the right behind the people, points to the centre of the galaxy. Because pulsars slow down at known rates, the map says not only where the spacecraft came from but roughly when.

At the right stand a man and a woman in front of an outline of the spacecraft, drawn to the same scale. The man has raised one hand. Beside the woman, between two short marks, is the binary number eight: eight times 21 centimetres, about 168 centimetres tall.

Along the bottom is the solar system, the Sun and its planets in a row, with their distances from the Sun written above and below in binary. Saturn has its rings. From the third planet a curved line runs out past Jupiter and ends in a small drawing of the spacecraft.

Some of it has aged. Pluto, drawn as a planet, has since been counted differently, and Pioneer 11 in fact flew on to Saturn, not straight out past Jupiter as the drawing shows. And as one critic pointed out, the arrow on that line is an old human sign that may mean little to anyone whose ancestors never hunted with bows. The last signal from Pioneer 10 reached Earth in January 2003. The plates themselves are still out there, unread, moving away from the Sun.