The Pioneer plaques are a pair of gold-anodized aluminum plaques which were placed on board the 1972 *Pioneer 10* and 1973 *Pioneer 11* spacecraft, featuring a pictorial message, in case either Pioneer 10 or 11 are intercepted by 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* spacecraft were the first human-built objects to leave the solar system. The plaques were attached to the spacecraft’s antenna support struts in a position that would shield them from erosion by stellar dust.

**1. **The image of a naked man and woman might prove meaningless scribbles to a life form that looks very different to our own.

**2. **Echoing Copernicus’s picture of the sun-centred solar system, Sagan and Drake drew a picture of the planets and included Pluto.

**3. **A picture of the Pioneer space probe at the end of a line emanating from the third planet of the Solar System tells aliens where the message comes from.

**4.** The numbers in the Pioneer plaque are binary – a vertical line for 1 and a horizontal line for 0. The numbers on planets indicate distance from the Sun.

**5. **There are further binary numbers. We write numbers in decimal because we have 10 fingers. Aliens probably have an entirely different anatomy.

**6. **The star map locates the Sun. The radial lines locate pulsars, stars emitting a regular electromagnetic pulse. A binary number shows the frequency.

**7.** This is a unit of measurement of time and distance. The circle represents a hydrogen atom. When the orbiting electron flips states it corresponds to a wave with frequency 1,420 MHz and wavelength 21cm. These are the diagram’s units of measurement.

**8.** The image of the Pioneer space probe gives aliens an idea of the height of humans relative to the probe.

**9. **The height of the woman is in binary: |- – – units of length. The unit of length is 21cm given by the wavelength of the hydrogen atom as it flips states. As 1000 is eight in binary, the woman’s height is 8x21cm=168cm.

This is a great web page. It presents the plaque in a non-technical format. That is wonderful for someone who does not have a technical background, or who is not into space.

Point 7, above, needs to be revised.

“7. The height of the woman is in binary: 1,000 units of length. ” You are correct that all the numbers and units are in binary. However, the height of the woman is 8 units of length, not 1000. A “1000” or “1 – – -” (the plaque uses dashes instead of zeros) means “8” in binary. You have it written as the decimal number 1,000 – the comma in the number causes confusion – otherwise everything’s perfect.

Thanks for your help. Post now updated.