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ZingPath: Weather Prediction

Boom! How Far is the Lightning?

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Boom! How Far is the Lightning?

Earth & Space Science

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Using the formula Distance = Speed x Time, learners calculate the distance between a lightning strike and an observer.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • After completing this Activity Object, learners will be able to:
  • Explain that in a thunderstorm, we often see a bolt of lightning before we hear its thunder.
  • Explain that in air, light travels might faster than sound.
  • Determine the distance of a lightning strike from an observer, using the formula Distance = Speed x Time.

Everything You'll Have Covered

When humid warm air rises and meets cooler air, the stage is set for a storm. Clouds form as moist warm air rises and swirls within the cool air, generating static electricity. The top of the storm cloud becomes positively charged, and the bottom of the cloud becomes negatively charged. Those negative charges at the bottom of the cloud induce positive charges on the ground below. When enough negative charges have gathered at the bottom of the cloud, they begin to move down from the cloud, and they attract positive charges that surge up from the ground, sparking cloud-to-ground lightning. Lightning can also be observed from clouds to bodies of water and within clouds. If enough static electricity is generated, lightning can also be found sometimes during dust storms, volcanic eruptions, and forest fires.

People have wondered since the beginning of time about the cause of thunder. Ancient religious poetry identified thunder as the voice of God. Greek philosopher Aristotle theorized in the third century BC that it was the sound of clouds colliding. By the middle of the nineteenth century, scientists hypothesized that lightning created a vacuum, thus producing the sound of thunder. In the twentieth century, scientists realized that the air surrounding a bolt of lightning can reach temperatures approaching 30,000C (54,000F) in a fraction of a second. Compare that to the temperature of the Sun's surface, 5,500-6,000C. That excessive heat causes the air around the lightning bolt to expand rapidly, creating sound waves we hear as thunder.

We can calculate our distance from a lightning strike by using the formula Distance = Speed x Time. Since light travels much faster than sound in air, the flash of lightning almost instantaneously reaches us during a storm, but the thundering sound reaches us later. An observer close to the strike sees the lightning and hears the thunder almost simultaneously. An observer at a distance first sees the lightning and then hears the thunder. The speed of light is about 300,000,000 meters per second, while sound travels at about 350 meters per second in air. The speed of sound can vary, though, depending on factors like temperature, humidity, and elevation. Even with such variations, light still travels much faster than sound in air, and we see the flash of lightning first and hear its thundering sound later.

Tutorial Details

Approximate Time 30 Minutes
Pre-requisite Concepts distance, position, solving for unknowns, speed, time of travel, using formulas
Course Earth & Space Science
Type of Tutorial Concept Development
Key Vocabulary calculation of distance, distance, equation