Electrical engineer Greg Leyh built the giant Tesla coil in this video, and wants to construct an even larger version: Two 10-story-high towers that would send lightning zinging across an area the length of a football field. New Scientist interviewed Leyh, to find out what the point of this is (besides the obvious inherent awesomeness):
Lightning can break down air up to five times more easily than normal electric arcs [between two oppositely charged rods in the lab], using tricks we don’t yet understand. However, recent theories and a few tantalising experimental results suggest that normal arcs start to gain lightning-like abilities once they grow past about 60 metres in length. If we can build a machine this large, we’ll very quickly arrive at a better understanding of what’s going on.