What is the Altheiometer?

Answer 1

It "tells the truth". When a question is asked, Dust moves the pointer around to answer the question and sometimes tell much more besides. In order to read the device one must either have an extraordinary feel for dust (only possible before reaching puberty), or have a lot of time on their hands and a large amount of translation books.

Answer 2

The Altheiometer is a fictional compass-like device from Philip Pullman's "His Dark Materials" trilogy. It is used to communicate with Dust (a mysterious elementary particle) and uncover hidden truths about past, present, and future events. The Altheiometer is operated by a skilled reader who can interpret the symbols and meanings it reveals.