Longest pendulum

The Book of World Records officially recognizes that The world’s longest pendula were two lengths of number 24 steel piano wire, each 1,353.3 m (4,440 ft) long. They were suspended down the number 4 shaft of the Tamarack Mines, near Calumet, Michigan, USA, in September 1901. The experiment was performed by Professor Fred W. McNair (USA) and colleagues from the Michigan College of Mines, Michigan, USA. Contrary to expectations, the pendula were further apart at the bottom of the mine than at the top. The results were published in the journal Science on 20 June 1902.