# Geek Trivia: What math error was accidentally built into the Pioneer Plaques?

Despite the extraordinary intellects working on the Pioneer Plaques, a math error crept into the design -- one that might prevent our future alien overlords from locating Earth.

Only two images appear on both Pioneer Plaques and both Voyager Golden Records: a two-dimensional depiction of the hyperfine transition of neutral hydrogen, and a binary pulsar map depicting the location of our sun. The latter has a non-trivial numerical inaccuracy in it, to the point that alien intelligence might have a slightly more difficult time finding dear old Earth.

The pulsar map in question look like an erratic burst of lines radiating from a central point. The center represents our sun, while each line represents the scale distance between our local tar and one of 14 selected pulsars. The lines are binary numeral strings denoting the period of each pulsar, so that aliens can know exactly which regularly radiating celestial object we're using as sign posts. Identify any three of the pulsars, and the map will direct you to our sun.

Unfortunately, the listed period of one of the pulsars on the Pioneer Plaques and Voyager Records is wrong. At the time of the Plaque's creation, pulsar "1240" (now known as J1243-6423) had a known period of 0.388 seconds. More specifically, the early 1970s astronomy community only knew the pulsar's period to three significant digits. Unfortunately, to be useful on the Pioneer Plaque, the binary listing for this pulsar had to be far more precise, to beyond 10 significant digits.

In other words, Drake and Sagan estimated pulsar 1240's period to a more precise degree, and in the subsequent 40 years, we've discovered their estimates were more than slightly wrong. Aliens may not recognize pulsar J1243-6423 as the pulsar described on the Pioneer Plaque map. Fortunately, any intelligence that could find and decode the map probably has a pretty fair knowledge of pulsars throughout the galaxy — and they have 13 other points of reference to help them along.

And for those of us who make occasional math errors and poor estimates, it's nice to know that even the best pros are fallible. Sometimes.

That's not just a moderately meaningful mathematical misstep; it's an insidiously inaccurate instance of interplanetary Geek Trivia.

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