Tuesday, May 28, 2013

Why doesn't lightning travel in a straight line

In the past, I have few attempts at shooting the lightning as it happen and none of my shots are decent enough, but one thing I observed is that lightning does not travel in a straight line.

Captured with Nikon D90 at | 38mm | f/18 | ISO-200 | 30 sec |


First, how lightning is formed

The zig-zagging path of lightning has its origin in processes still not fully understood. It begins with strong rising currents of air creating a static electric charge through frictional effects somewhat like those on the surface of balloons rubbed on suitable fabric. Recall the Van der Graaff effect?

This charge generates an electric field that accelerates any free electrons in the surrounding air, smashing them into neighbouring molecules, thus releasing yet more electrons.


. . . and the zig-zag?

If sufficiently violent, these collisions will turn the air under the cloud (see pic above) from electrically insulating to conducting, which allows the passage of electrical current. This heats up the air to around 30,000oC, triggering the characteristic flash light that follows the zig-zag path formed by the collisions.

The heat also causes a sudden expansion of the air, which we hear as a clap of thunder. The thunder 'loudness' corresponds with the amount of electrical current passing through the air.

In short: Molecules and electrons collisions are in random directions, so the lightning flash you see in the sky is not in a straight line, too.

3 comments:

Sunset lover said...

I've been wondering too.
Light travels in a straight line, so, why shouldn't lightning.

thomas said...

nicely captured,it can be dangerous trying to capture these lightning.

de engineur said...

Thanks.
Yeah I suppose it is. We have to be careful.