Thursday, February 17, 2011

Catching A Lightning

This is a fascinating interview with physicist Joseph Dwyer, who studies lightning. It's a wonderful interview because you also learn a bit of the physics of lightning, and why it isn't identical to the spark one gets due to static electricity.

But isn't it just an electrical discharge between thunderclouds and the ground?
In a sense, but the big problem is that to get a spark, air needs to break down. It needs to stop being an insulator and start being a conductor. We commonly experience this if you touch a doorknob and you get a spark between your finger and the doorknob. What happens is the charges get concentrated into your fingertip and you get a big electric field. Then, as your finger approaches, the conventional breakdown field is reached, which is about 3 million volts per metre – and then air sparks.

The problem is if you look up inside thunderclouds, the breakdown field that you need to make a spark is never found. People have been launching balloons for decades, they've been flying airplanes, they've been launching rockets...but the fields they record are not even close to this strength.


No comments: