Thunderbolts and Lightning

SCIENCE

Everyone knows what lightning sounds like: thunder. Now, for the first time, scientists have turned a thunderclap into an image. (Nature)

Thunderbolts and lightning, very very enlightening . . . Learn more with our encyclopedic entry.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

The video shows the lightning, the image below shows the thunder.

©2015 Southwest Research Institute®

©2015 Southwest Research Institute®

Discussion Ideas

  • Scientists recently visualized thunder. Why is this a big deal?
    • Thunder is a sound, not a sight! Thunder is the loud sound that follows a flash of lightning.

 

  • How is thunder produced? Read through the short, excellent Nature article or the first part of our own short encyclopedic entry on lightning for some help.
    • According to Nature, “Lightning forms when electrical charges separate and build up between the clouds and the ground, or inside the clouds themselves. Thunder is the sound that is created when the resulting lightning strike suddenly heats the air.” Specifically:
      • In a thundercloud, ice and a slushy mixture called graupel interact. Ice tends to develop a positive charge, meaning the icy region of the cloud has more protons and neutrons than electrons. The graupel tends to develop an overall negative charge, meaning there are more electrons. Positive charges and negative charges attract each other, and thunderclouds are full of these electrical charges connecting. Lightning is the electric discharge produced by these connections.
      • The connections also create thunder. Thunder is a shock wave caused by the sudden expansion of air in and around the path of lightning’s superhot electrical discharge.

 

  • How did scientists conduct their experiment? (Do not try this at home!)
    • First, they went to Florida, the most lightning-prone state in the U.S.!
    • Next, they set up a line of 15 microphones, each spaced one meter (3.3 feet) apart, about 95 meters (about 310 feet) from a rocket launch pad.
    • Then, during a thunderstorm, they launched a small rocket trailing a grounded copper wire into thunderclouds. (You can see it launch in the video.) According to the Southwest Research Institute, “The copper wire provides a conductive channel and creates a predictable path for lightning, allowing scientists to precisely focus their instruments and perform repeatable experiments close to the discharge channel.”
    • According to this great article from CNET, “data captured by the microphone array was then used to create a visual representation of the sound produced by the lightning traveling down the copper wire.”

 

©2015 Southwest Research Institute®

This image shows the triggered lightning strike at left and the acoustic images of the thunder at right. The “RS” in the graphs stands for return stroke—the actual “bright visible flash that we see as lightning,” according to the National Weather Service. The triggered event had nine return strokes, visible as purple in the image at left. “dB” stands for decibel, the unit used to measure the intensity of a sound or the power level of an electrical signal.
©2015 Southwest Research Institute®

  • Take a look at the image above. The “images” of thunder are on the right. Why is thunder red?
    • Because that’s what the scientists wanted it to be! The colors are were assigned by researchers, not nature.
    • The scientists are much less interested in assigning color, and much more interested in visualizing data about how fast and at what height thunder travels. (Time is on the horizontal x-axis, while elevation is on the vertical y-axis.)

 

TEACHERS’ TOOLKIT

Nature: Images expose thunder in exquisite detail

CNET: Take a look at the very first images of thunder

Nat Geo: What is lightning?

Southwest Research Institute: SwRI reveals the first “images” of thunder

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