How Is Thunder & Lightning Made?

Lightning is a huge electrical spark. Thunder is the sound produced by lighting.

The water or ice particles in clouds build up an electrical charge by bumping into one another, just like you can build up a charge by rubbing your feet on carpet when you are wearing socks, or when you peel a piece of sticky tape (the effect is called triboelectricity, whenever two dissimilar materials touch, there will be some transfer of electric charge). Usually the base of the cloud builds up a negative charge. This negative charge in the cloud 'induces' a positive charge in the ground below it. An electric field is created between them. When the charge is great enough, the electric field is strong enough to cause the molecules in the air to begin to become electrically conductive. This happens in a number of stages, and is very complex in nature, but it all occurs in the time of a few milliseconds. When there is a conductive channel between the cloud charges and the ground, a large pulse of electrical current flows, which lights up the channel and heats it to tens of thousands of degrees. This is what you see when you see lighting. The pulse of electric current can be up to 30000 amperes and lasts for a few milliseconds. Sometimes there can be multiple pulses throught the same conductive channel (this gives the flickering you sometimes see with lightning). The sudden increase in temperature of the air to 10s of thousands of degrees celcius causes it to rapidly expand and produces a shockwave (like an explosion). This is what you hear when you hear thunder. Near by it sounds like an extremely loud bang or crack, like an explosion or a bomb exploding. At a distance, you hear many echoes spaced slightly appart, which gives the drawn out rumbling effect.