A Review of Lightning, Tornadoes, and Storms Demonstration


Cartoon icon of Science Guy in stormWhat makes water evaporate? What’s the difference between a hurricane and a tornado? Where is the safest place to be in a lightning storm or tornado? These questions (and scientific curiosity in general) brought students—like Maria, who is interested in rockets, and Patrick, who likes studying animals' minds, and Jacqueline, Nicholas, and Patrick, who had been to two previous Science on Saturday presentations, and James, who had been to four—to Lincoln Laboratory for Robert Hallowell's presentation about meteorology on February 7, 2009.

Hallowell, a staff member in the Laboratory's Weather Sensing Group, explained that weather is all around us, like a big ocean of air that the earth's rotation keeps moving. He described the basic elements of weather—pressure, precipitation, wind, clouds, temperature, and humidity—and demonstrated them all with the help of his assistants Mike Matthews, Colleen Reiche, Kathy Carusone, Dave Clark, Kim Calden, and Pat Pawlak, as well as several young volunteers from the audience. For instance, two students were able to float ping-pong balls sitting on a low-pressure column of air generated by a leaf blower. In another demonstration, three students were asked to take the temperature three different ways: with an infrared pointing device, a digital thermometer, and a thermometer with colored alcohol. Hallowell explained that all thermometers work on a similar principal by measuring the expansion of materials or speeding up of energy caused by increases in temperature of the object. He demonstrated the concept with a large outside dial thermometer with a spring in the back that got tighter in cold temperatures and expanded in warm temperatures. However, only two of the thermometers read the same. The third differed by a degree, an early demonstration that because of all the forces of nature, many times a weather forecaster has challenges simply measuring what the weather is doing now, let alone what it will do in the future.

In his explanation of humidity, Hallowell told his audience that the air in the auditorium could contain as little as a watering can filled with moisture on a cold dry winter day, or as much as thirty-five gallons on a hot humid summer day. He also showed how to make fog in an aquarium and how to make it rise, by having a volunteer turn on the sun—that is, with a heat lamp standing in for the sun. The sun-heated air expanded, causing the clouds to rise up out of the aquarium to where drier air mixed in and evaporated the clouds. Three volunteers tried their luck at measuring wind speed with an anemometer. One volunteer yelled out the speed while the other two used progressively stronger winds (breath, a small fan, a hair dryer, and a leaf blower). Several members of the audience found themselves in a shower of hail (as enacted by ping-pong balls) that Hallowell predicted for the center of the audience. Some hail fell outside the predicted zone, while others in the prediction area received none—Hallowell used this hailstorm to illustrate the challenge of forecasting weather. Hallowell then explained the components of a thunderstorm, showed a movie of a tornado blowing down a shed, and, in a less destructive experiment indoors, used a cool-mist humidifier, a bucket of water, and a fan to make a miniature tornado. An audience volunteer was able to stop it easily with a piece of cardboard over the fan to cut off the tornado's energy. Hallowell went on to explain that hurricanes are vortices like tornadoes, only over much larger and longer scales, and that their main source of energy is a large area of warm moist air rising from the surface. A volunteer showed how the vortex could just as easily be stopped by placing the cardboard over the warm water below, just as a hurricane loses strength over land.

Earle Williams, an expert on lightning who works at the Laboratory, came forward to explain what creates lightning. With the help of a Van de Graaff generator, Williams demonstrated the principles of electrostatic repulsion and gave a volunteer an interesting new hairdo. A final event that involved heavy audience participation and a great many paper bags produced a series of small individual thunderclaps in the first show. Then young members of the audience came to the front after the show to ask more questions, to find out how to build a Van de Graaff generator at home, and to try out the anemometer. Ben was able to produce 15 mph winds, while Jasper, a volunteer from the previous robotics show, and his brother, Dexter, came down to look over the some of the other measuring equipment. In the meantime, staff members asked to have the ping-pong balls returned for the next show's hailstorm, and they prepared to help Hallowell entertain and instruct the next audience. In the second show, air-filled paper bags popped in concert to resemble thunder and made a big enough sound to bring Emma, a young audience member, back into the auditorium to find the source of the big finish of the second presentation of "Lightning, Tornadoes, and Storms."

By the way, if you find yourself in a tornado, the safest place is in the basement or the bathtub.


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