5.2 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Pioneer plaque | 1/3 | https://en.wikipedia.org/wiki/Pioneer_plaque | reference | science, encyclopedia | 2026-05-05T13:17:22.529729+00:00 | kb-cron |
The Pioneer plaques are a pair of gold-anodized aluminium plaques that were placed on board the 1972 Pioneer 10 and 1973 Pioneer 11 spacecraft, featuring a pictorial message, in case either Pioneer 10 or 11 is intercepted by intelligent extraterrestrial life. The plaques show the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft. The Pioneer 10 and 11 spacecraft were the first human-built objects to achieve escape velocity from the Solar System. The plaques were attached to the spacecraft's antenna support struts in a position that would shield them from erosion by interstellar dust.
== History == The original idea, that the Pioneer spacecraft should carry a message from mankind, was first mentioned by Eric Burgess when he visited the Jet Propulsion Laboratory in Pasadena, California, during the Mariner 9 mission. He approached Carl Sagan, who had lectured about communication with intelligent extraterrestrials at a conference in Crimea. Sagan was enthusiastic about the idea of sending a message with the Pioneer spacecraft. NASA agreed to the plan and gave him three weeks to prepare a message. Together with Frank Drake he designed the plaque, and the artwork was prepared by Linda Salzman Sagan, who was Sagan's wife at the time. Additional artistic contributions were made by Jon Lomberg. Both plaques were manufactured at Precision Engravers, San Carlos, California. The first plaque was launched with Pioneer 10 on March 2, 1972, and the second followed with Pioneer 11 on April 5, 1973. In May 2017, a limited edition of 200 replicas engraved from the original master design at Precision Engravers was made available in a Kickstarter Campaign, which also offered laser-engraved replicas.
== Physical properties == Material: 6061 T6 gold-anodized aluminium Width: 9 inches (228.6 mm) Height: 6 inches (152.4 mm) Thickness: 0.05 inches (1.27 mm) Mean depth of engraving: 0.015 inches (0.381 mm) Mass: approx. 4.2 ounces (120 g)
== Symbolism ==
=== Hyperfine transition of neutral hydrogen ===
At the top left of the plaque is a schematic representation of the hyperfine transition of hydrogen, which is the most abundant element in the universe. The spin-flip transition of a hydrogen atom's electron has a frequency of about 1420.405 MHz, which corresponds to a period of 0.704 ns. Light at this frequency has a vacuum wavelength of 21.106 centimetres (8.309 in) (which is also the distance the light travels in that time period). Below the symbol, the small vertical line—representing the binary digit 1—specifies a unit of length (21 cm) as well as a unit of time (0.7 ns). Both units are used as measurements in the other symbols.
=== Figures of a man and a woman ===
On the right side of the plaque, a nude man and woman are shown in front of the spacecraft. Between the brackets that indicate the height of the woman, the binary representation of the number 8 can be seen (1000). In units of the wavelength of the hyperfine transition of hydrogen this means 8 × 21 cm = 1.68 meters (5 ft 6 in). These together indicate the scale of the humans relative to the craft itself. The small defect in the first zero is only in reproductions of the plaque (like here) and not on the original. It probably dates back to a printing error in the original article "A Message from Earth" which is the primary source for many of the copies of the engraving. In the replicas from the 2017 Kickstarter campaign mentioned above the delineation is correct. The right hand of the man is raised as a sign of good will. Although this gesture may not be understood, it offers a way to show the opposable thumb and how the limbs can be moved. Originally Sagan intended the humans to be shown holding hands, but soon realized that an extraterrestrial might perceive them as a single creature rather than two organisms. The original drawings of the figures were based on drawings by Leonardo da Vinci and Greek sculptures. The woman's genitals are not depicted in detail; only the mons pubis is shown. It has been claimed that Sagan, having little time to complete the plaque, suspected that NASA would have rejected a more intricate drawing and therefore made a compromise just to be safe. Sagan said that the decision to not include the vertical line on the woman's genitalia (pudendal cleft) which would be caused by the intersection of the labia majora was due to two reasons. First, Greek sculptures of women do not include that line. Second, Sagan believed that a design with such an explicit depiction of a woman's genitalia would be considered too obscene to be approved by NASA. According to the memoirs of Robert S. Kraemer, however, the original design that was presented to NASA headquarters included a line which indicated the woman's vulva, and this line was erased as a condition for approval of the design by John Naugle, former head of NASA's Office of Space Science and the agency's former chief scientist.
=== Sun and galactic landmarks ===