The distinctive blue-white color of lightning is caused by light emitted as the electrons drop back to their original energy states.
Nitrogen, the dominant gas in the atmosphere, is excited by this strong flow of energy, its electrons moving to higher energy states. Lightning is visible as a flash of light because of both incandescence (due to its high temperature it glows blue-white) and luminescence (excitation of nitrogen gas in the atmosphere). The flash reaches temperatures of about 30,000 K. In successive discharges, surrounding pockets of charge in the cloud follow this path to earth.
#Blue and red lightning free
Once the first of these leaders reaches the ground, the electrostatic forces are free to flow to earth in a brief and high-voltage discharge. In a chain reaction, "leaders" form tracks spreading like branches through the air below the cloud, breaking down the air molecules into charged particles.
For a time, the air insulates them from each other, but then the electrostatic difference reaches a point where the electric flash begins to form. Pockets of positive and negative charge develop within the cloud, and eventually reach a size big enough to induce an opposite charge at a point on the ground below.
Electrical excitation is at play in both the lightning and the bridge, which is lit with vapor lamps.įorked lightning is a huge discharge of electricity between heavy cumulonimbus clouds and the ground. Above right, lightning dances across the charged skies over Sydney Harbour and the Harbour Bridge.
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