In 2004, Richard Box slipped a local farmer £200 to "borrow" a 3,600 m2 field to plant fluorescent light tubes near overhead power lines. The show began at night:
A fluorescent tube glows when an electrical voltage is set up across it. The electric field set up inside the tube excites atoms of mercury gas, making them emit ultraviolet light. This invisible light strikes the phosphor coating on the glass tube, making it glow. Because power lines are typically 400,000 volts, and Earth is at an electrical potential voltage of zero volts, pylons create electric fields between the cables they carry and the ground.
Box denies that he aimed to draw attention to the potential dangers of power lines, ‘For me, it was just the amazement of taking something that’s invisible and making it visible,’ he says. ‘When it worked, I thought: ‘This is amazing.’’
http://www.zen54564.zen.co.uk/r/index.htm - via Gizmodo