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A compass that lights the way

Instrument senses magnetic field direction optically

By
4:00pm, September 20, 2010

A compass made of light promises to be more sensitive than anything in a boy scout’s wildest dreams. A light beam shot through a blob of rubidium atoms can directly and reliably measure the size and orientation of a magnetic field, a team of physicists reports in the Sept. 13 Physical Review A.

Highly sensitive compasses are needed for oil discovery, earthquake detection and navigation (in the catastrophic event of a GPS failure, that is). Recently, highly sensitive compasses guided engineers as they drilled relief wells in the Gulf of Mexico after the Deepwater Horizon blowout. 

These compasses are very good at finding the size of a magnetic field, but typically have to be tweaked to include a built-in local reference magnetic field so that they can also find the field’s direction. This comparison of the external field to an internal reference allows the compass to reconstruct the magnetic field, but the quality of the data can

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