Science And Environment: How Lightning Works

Learn what lightning is, what causes it and what it can do.

What is lightning?

Lightning is a bright bolt of electricity that emanates from the clouds in a thunderstorm. Lightning usually appears as a streak of light, often with smaller forks of light emanating from it. This is generally called forked or streaked lightning. Sometimes the lightning occurs inside the cloud and this generally causes the entire cloud to light up with a glow instead of a visible streak. A thunderstorm will often have multiple lightning bolts, leading to what can be an incredible light show.

Despite what many people believe, lightning can occur even when there is no rain. The conditions in the atmosphere simply have to be correct for lightning to strike.

What causes lightning?

The moving air during a thunderstorm separates the negative and positive charges in a cloud. Once the charges are separated, they move around in the cloud creating additional buildup and discharge of electricity. Often, the positive charges move upward to the top of the cloud while the negative charges try to move downward. The charges find a path of ionized air molecules and follow them toward the ground. This causes a bolt of lightning.



When a lightning bolt moves from the cloud to the ground, the air near the ground starts to glow before the particles closer to the cloud. But, they all start to glow so quickly - it takes about 1/10,0000th of a second - it appears to light up all at the same time.

As more of the charges move around and positive are torn apart from negative the electricity affects the nearby air creating more fragments with electrical charges.

The old adage that lightning never strikes twice in the same place is incorrect. It is very common for lightning to strike again and again in the same location; as long as the same conditions that attract a lightning bolt to hit initially are still in place, it will continue to be a conducive location. Often multiple lightning strikes in one location will occur sequentially in a single charged cloud.

What is thunder?

The sound of thunder is caused by air near lightning being quickly heated and cooled. The rapid change in temperature causes an explosive shock wave in the air that makes the loud boom known as thunder.

Lightning safety:

Lightning is very powerful. A single bolt of lightning can contain 250-kilowatt hours of energy and can be as hot as the surface of the sun. So, being hit by a lightning strike not only packs a punch, it includes extreme burns.

When lightning is spotted or thunder is heard, it is important for people to seek safe locations. The safest place during a lightning storm is inside a tall building with lightning rods. Avoid using electrical appliances and phones during lightning storms since a strike to the exterior wires can send a charge inside. In fact, it is wise to unplug appliances during lightning storms since a surge of electricity from a lightning strike can ruin many household electronics.

Avoid touching water during a lightning strike, either indoors or outdoors. Water conducts electricity and can be very dangerous during a storm. It is best to seek a safe interior location during a storm. Listen to a battery-operated radio or watch a battery-operated television for updates on the weather conditions to determine when it is safe to venture outdoors again.

Outdoors, avoid standing near or touching natural lightning rods; do not stand near or under trees or picnic shelters, do not hold golf clubs or other metal implements. Avoid being the highest object in an area; instead stay low and seek low ground.

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