An alethiometer is a fictional device from Phillip Pullman's fantasy novel trilogy His Dark Materials which tells the truth. The word "alethiometer" comes from the Greek word aletheia, meaning "truth", so "alethiometer" means "truth-measuring instrument". The resemblance of the device to a large compass caused the American publishers of the first book, originally entitled Northern Lights, to retitle the book The Golden Compass. It is described in Northern Lights thus:
The alethiometer is given to the leading character, Lyra Belacqua, by The Master of Jordan College. He tells her that it is a rare device, being only one of six ever made. He also explains its function to her, and says she'll have to learn how to use it by herself.
To use the alethiometer, the user directs three needles to lie over certain symbols on the face of device, and forms a question in his or her mind. The fourth needle then responds to the question, swinging over different symbols to form answers. Any given...
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