You all remember when on a dry winter day you shuffle along your carpeted living room floor and then touch somebody with your extended finger. You may have seen a little spark. That's a lightning bolt on a small scale (the sensation may not be too pleasant - but that's a sacrifice needed in the name of science). Now, in the lightning in the sky, your shuffling on the carpet is replaced by a vigorous wind rushing past rain drops and ice particles (yes - it's cold where the clouds are) and the result is a spontaneous lightning flash. Physicists describe this as positive (+) and negative (-) electric charges which are separated by the wind and reunite with a sudden flash.

What about the thunder? That's even easier to demonstrate: Just clap your hands, or better still, let an adult do it. Their hands are bigger. The demonstration works best if the hands are cupped so they catch some air between them: Bang! In the sky, the lightning flash will heat the air in its path. That will make it expand. You can show that also at home: Put an inflated rubber balloon into the warm oven (careful: not too hot - your mother doesn't like bits of rubber stuck to its walls). When you take the balloon out, you notice that it has grown bigger. When it cools, it shrinks again. The same occurs when the lightning flash is moving through the air. When the air cools off afterwards, it rushes back together and: Boom - the clapping of the hands in the cloud of a thunderstorm!

There are many other questions, for example: Why do the lightning bolt and the thunder sometimes occur simultaneously, and sometimes not, and why does even the fastest moving car seem motionless when illuminated by a lightning bolt? Think about it!