Ya know, I was just reading the topic on ball lightning and I really have to rant a little here. I saw a Discovery Channel or TLC show in the past year or so about lightning. They said that same thing about lightning “starting on the ground,” which I think is true in that there are tendrils (is that the right word?) which come up from the ground first–like the static-ish sparks you can barely see coming off a Van de Graaff generator.
Now, the thing that annoyed the hell out of me was when they claimed they actually captured a picture of the lighning starting on the ground with their cameras (they videotaped a staged lightning strike where model rockets with are sent up with thin wire to make lightning strike where a particular location.) They showed a freeze-frame of their video showing the lightning only in the bottom half of the picture.
This is stupid.
The area in frame was about 100 feet high. An electric spark crawling along through air at 0.1c is going at roughly 20,000 miles per second, so it would traverse the 100 feet in about 1 microsecond. The camera, in the mean time, is scanning one video field every 60th of a second, so basically they just demonstrated the scanning properties of the camera.
What actually happened is as follows. The camera was running, scanning a field at a time every 60th of a second, and (because of persistence of vision) making 30 frames per second. The camera would scan its imager from left-to-right, top-to-bottom in 1/60th of a second to make one full trip. In one of these fields, it made it about halfway down the imager when the lightning struck. All the air around the lightning spark started glowing within 1 millionth of a second between the top of the frame and the bottom. The camera continued on its merry way scanning its imager, but this time there was a big bolt of lightning right smack in the middle.
The resulting image looks like the camera captured half a frame-worth of a bolt of lightning.
My beef with this is that they didn’t realize what I said was the case. They had a bunch of videographers and scientists at their beck and call yet none were smart enough to know this. Ugh.