The Levitron gets touted as an "anti-gravity" device--and in a way, it is.

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On a lark, Mr. Minsky spent some time "inventing useless things, " he says, such as a "gravity machine, " a device that would ring a bell if the force of gravity changed.

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At Purdue University in Indiana, scientists are working on a reactor-like device that uses water circulated by gravity to keep the core cool.

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By measuring the amount of static acceleration due to gravity, the chip knows the angle a device is being tilted at with respect to the earth.

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