#711: Seismograph

XKCD comic, described below.
Transcript

[[A man is standing over another man, who is strapped into a chair with wires attached to his head and arms. The wires lead to a large lie detector on a stand next to him, which has jagged lines drawn across it.]] Standing man: IS THERE AN EARTHQUAKE HAPPENING?! Sitting man: No! <<SCRITCH SCRITCH>> Pro Tip: In a pinch, a lie detector can double as a seismograph.

The reverse only works if the subject has a nervous twitch.

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