Measurements taken early this week showed the hole measured 324 feet in diameter and is 50 feet deep, but in one corner it goes down 422 feet, said John Boudreaux, director of the Office of Homeland Security in Assumption Parish, about 30 miles south of Baton Rouge.

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Astronomers have measured the rate of spin of a supermassive black hole for the first time - and it is big.

BBC: First glimpse of a black hole's spin

Apparently the string of logging tools, each one measuring something different, needs some room to take their readings so the "rat hole" has to extend below the measured area.

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