Story at a glance
- The electrical charges that build up in a storm release in the form of lightning.
- This causes the surrounding air to heat up to around 54,000 degrees F. The air rapidly expands, compressing the air in front of it.
- Thunder is the acoustic soundwave created by this rapid expansion and contraction of air.
AUSTIN (KXAN) – Have you ever wondered why thunder has different sounds? A crack versus a rumble? Shocking energy versus calm low? Let’s dive into…
The basics: what is thunder?
The electrical charges that build up in a storm release in the form of lightning. The intense heat generated by this electrical discharge has the air surrounding the lightning channel superheating to about 54,000 degrees Fahrenheit (that’s about five times the surface temperature of the sun!)
All gases expand when the temperature increases, so when lightning heats the air for just a fraction of a second, the air expands so fast that it compresses the air in front of it. Thunder is the acoustic soundwave created by this rapid expansion and contraction of air.
MORE: Lightning is often seen before thunder is heard because light travels faster than sound.
What affects the sound of thunder?
Sound waves move faster in warm air compared to cold air and refract or bend towards areas of low pressure. Because our atmosphere generally cools with height, these sound waves tend to bend upward, making it harder for someone further away from the point of the lightning to hear the thunder. Humidity also plays a role as a more humid environment will bend or block more sound waves.
Sounds of thunder
a”cracks” usually indicates a near or relatively near thunderstorm and/or a vertical strike on a person (ex. lightning bolt from cloud to ground).
a”Q” is usually associated with storms that are further away and/or with a strike parallel to a person (ex. lightning bolt from one end of the cloud to another).
a”boom” is a sign of lightning that has reached the earth.
A combination of “crack” and “rumbling” is heard when sound waves from multiple strikes reach a person at different times.
Myth or not?
Lightning never strikes the same place twice.
MYTH. The Empire State Building in New York is said to be struck by lightning an average of 25 times a year.
If I can’t see the storm, I won’t get struck by lightning.
MYTH. Lightning can strike up to 10-12 miles away from its parent storm, hence the term “bolts from the blue.”
I can survive lightning.
TRUE. But the effects are likely. Ninety percent of people struck by lightning survive but often suffer long-term injuries.
Every thunderstorm has lightning, and safety is best achieved by staying indoors when a storm is in the area. A building with four walls and a roof qualifies as “inside” (not a baseball dugout, not under an overhang or under a tree, etc.)
In 2022, Texas ranked #1 as the state with the most lightning strikes (27.7 million).
How does lightning strike a person?
There are five ways lightning can strike a person:
- Direct strike – A person becomes part of the lightning discharge channel.
- Flash to the side – Lightning strikes a tall object and part of the current jumps to a person nearby.
- Lead to the ground – Lightning strikes an object and the energy travels through and along the surface of the earth.
- Conduction – Lightning strikes metal or cables, giving way for the force to follow.
- Streamers – A downward moving lightning channel connects the so-called a streamer, a positively-charged channel of air right above a tall object on the ground. When a streamer makes a connection to the main channel, all nearby streamers will exit.
Click here for lightning animations.
How is it spelled?
Lightning. Nothing e.
To lighten is to make something lighter (less weight). Lightning is what happens in a thunderstorm.
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