What is lightning?
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Clouds look fluffy and innocent but are active places. Water and ice are moving around inside forced up by warm air currents, down by gravity, and condensing and evaporating in the cloud. Just like rubbing a balloon can create static
electricity, the particles in the cloud become charged. It’s not clear how it happens but charge separates in a cloud with positive moving up and negatives down.
Once a significant charge separation has built up, the cloud can induce a positive charge in the ground. Step leaders form reaching out to the ground. They can cause a purplish glow as they ionise the air. They don’t go by the shortest route just the easiest, dust and other things in the air will affect the pathway. Streamers can come up from the ground to meet them. Once a pathway is completed the spark forms neutralizing the charge. As the negative charge races down the air heats up usually at the ground end first and a light races up to the cloud.
As the spark is very hot, as much as 20,000 degrees, it heats the air quickly causing a shock wave and thunder. Light travels very fast 186,000 miles per sec. Sound only at 1 mile for 4.5 secs. To find out how far away the storm is count after the lightning for every 4.5 secs the storm is 1 mile away.
There is a slow motion video of lightning here.
Watch closely and you will see the step leaders heading down from the cloud. These are rarely visible and last only a few thousandths of a second. Note that one reaches the ground and this is the path that the much brighter lightning bolt follows.
Lightning facts
• At any time there are over 2,000 thunderstorms occurring worldwide, each producing over a 100 lightning strikes a second. Thats over 8 million lightning bolts every day.
• Each lightning flash is about 3 miles long but only about a centimetre wide.
• A lightning strike discharges about 1-10 billion joules of energy and produces a current of some 30,000 - 50,000 amps, which heats the surrounding air to over 20,000 degrees Celsius,
• A single lightning bolt unleashes as much energy as blowing up a ton of TNT.
• A strike is actually made up of between three and twelve individual lightning 'strokes', each lasting only a few thousandths of a second.
