What is lightning?

Clouds may look fluffy and innocent, but they are actually active places. At their most exciting, they can create the wondrous effect of lightning.


How is lightning formed?

Water and ice move around inside the cloud; forced up by warm air currents, down by gravity, and compressed in the cloud. Just as rubbing a balloon can create static electricity, the particles in the cloud become charged. It’s not clear how it happens, but charges separate in the cloud. Positive charges move up, and negatives move down.

Once a significant charge separation has built up, the positive and negative charges seek to reach each other an neutralise. ‘Streamers’ come up from the ground to form a pathway. Once a pathway is completed a spark forms, neutralizing the charge.

As the negative charge races down, the air surrounding it heats up.The spark is very hot at almost 20,000 degrees Celsius, and it rapidly heats the air to create a shock wave.

Considering light travels very fast – about 300 million metres per second, and that sound only travels at 300 metres per second; light is a million times faster than the sound produced. To find out how far away the storm is, you can count how long you hear the sound after the lightning. For every 4 seconds between the flash and the rumble, the thunderstorm is 1 mile away.


Here is a slow motion video of lightning.

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.
  • That’s 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 30,000 – 50,000 amps.
  • 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.


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