| From classbrain.com|
By Cynthia Kirkeby
Oct 16, 2006, 07:58
What is ball lightning?
Ball lightning is an unusual phenomena that some people say doesn't exist, but there seems to be more and more evidence to show it does.
Here is an image of ball lightening from www.unusualresearch.com:
According to Associate Professor John Abrahamson, a chemical engineer at the University of Canterbury in Christchurch:
"Ball lightning appears as a glowing, hovering ball of light that moves slowly near the ground before disappearing or exploding. The ball usually measures about 30 cm in diameter, although two park rangers in the Australian outback reported seeing one in 1987 that was 100 metres wide.
There are hundreds of theories about why ball lightning occurs, said Associate Professor Abrahamson - but according to his theory, there are several basic requirements.
- The first is regular lightning.
- Second, the lightning must hit a structure such as a building, soil, or a tree. The struck object must have a metallic or an oxide component.
"Soil contains silicon oxide and carbon," Associate Professor Abrahamson explained. "The lightning reduces this to silicon metal, which is how we make silicon industrially." The silicon vapour condenses to form silicon nanospheres, which collect together in long strings.
- The third requirement is the presence of 'fulgerides' - long sausage-like holes in the soil full of hot vapour. These are created by lightning hitting the ground. "The lightning strike on soil digs a hole in the ground, forming a very hot channel," said Associate Professor Abrahamson. Geologists have dug them up afterwards and found them to be made of frozen molten glass oxides, often in the form of tubes. The silicon vapour is then ejected back out of the soil, forming a vortex ring - "like a smoker's puff" -
which forms a sphere. Once in this shape, the ball can move long distances, said Associate Professor Abrahamson."
Read more about it here:
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