NASA - Pioneer X Plaque

National Aeronautics and Space Administration

The Pioneer 10 spacecraft, destined to be the first man-made object to escape
our solar system, carries this plaque. It is designed to show scientifically
educated inhabitants of some other star system-who might intercept it millions
of years from now-when Pioneer was launched, from where, and by what kind of
beings. The design is engraved into a gold-anodized aluminum plate, 152 by 229
millimeters (6 by 9 inches), attached to the spacecraft's antenna support
struts in a position to help shield it from erosion by interstellar dust.

At the far right, the bracketing bars (1) show the height of the woman
compared to the spacecraft. The figure indicated by (2) represents a reverse
in the direction of spin of the electron in a hydrogen atom. This transition
puts out a characteristic radio wave 21 cm long, so we are indicating that 21
cm is our base length. The horizontal and vertical ticks (3) are a
representation of the number 8 in binary form. Therefore, the woman is 8 x
21 cm = 168 cm, or about 5'5" tall. The human figures represent the type of
creature that created Pioneer. The man's hand is raised in a gesture of good

The radial pattern (4) will help other scientists locate our solar system in
the galaxy. The solid bars indicate distance, with the horizontal bar (5),
denoting the distance from the Sun to the galactic center. The shorter solid
bars represent directions and distances to various pulsars from our Sun, and
the ticks following them are the periods of the pulsars in binary form.
Pulsars are known to be slowing down and if the rate of slowing is constant, an
other-world scientist should be able to roughly deduce the time Pioneer was
launched. Thus, we have placed ourselves approximately in both space and time.
The drawing at the bottom (6) indicates our solar system. The ticks
accompanying each planet are the relative distance in binary form of that
planet to the Sun. Pioneer's trajectory is shown as starting from the third
planet, Earth.