The 100-foot-long MINOS detector consists of 486 massive octagonal planes, lined up like the slices of a loaf of bread. Each plane consists of a sheet of steel about 25 feet high and one inch thick, covered on one side with a layer of scintillating plastic. The planes are numbered 0 through 485, with the last one visible in the photo. The whole detector weighs 6,000 tons.