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Many middle and high school teachers use science-based television shows in their classrooms, sometimes to give students something to do when a substitute is needed, other times to show demonstrations that are too expensive or dangerous to do in person. As a high school physics teacher, I was a fan of Nova, Scientific American Frontiers, and Bill Nye the Science Guy, but my current addiction is MythBusters.
For those of you unfamiliar with the show, MythBusters is a Discovery Channel program where special effects professionals Adam Savage (the one with big black glasses) and Jamie Hyneman (the one with the moustache and beret) test the truth of urban legends, TV commercials, and movie special effects. They are assisted by cohosts Grant Imahara, Kari Byron, and Tory Belleci, as well as gun and explosives experts as needed. Based on conversations I’ve had at NSTA meetings, quite a few of you are using MythBusters in your classes. I think Adam and Jamie are doing a lot of good work making science popular with the public. At the same time, almost every episode has at least one mistake or missed opportunity that would make it an even better resource for teachers.
Many segments on the show address free fall in one form or another, and I appreciate the effort they go to in starting small and working their way up to dropping things out of airplanes. Free fall is used (and abused) quite a bit in movies, as regular readers of this column might have noticed (see Journey to the Center of the Earth, for example). In a recent episode testing a luxury car commercial’s claim that their car was “faster than gravity,” the MythBusters dealt with terminal velocity, the speed at which a falling object stops accelerating in free fall. At that speed, the magnitude of the wind resistance pushing up is the same as the magnitude of gravity pulling down. The net force is zero, so the acceleration is zero. There was even a nifty animation of a falling Tory with force arrows changing as he sped up. Unfortunately, they showed the gravity arrow shrinking and the air resistance arrow growing until both were the same size. Unless he was losing weight as he fell, the force of gravity on Tory would remain constant, so the animation should have shown the wind resistance arrow increasing in size. I enjoyed the rest of the episode (several cars were dropped and destroyed) but that force diagram was frustrating.
In other reviews, I have noted movie-makers seem to have difficulty with the idea of inertia (Indiana Jones is the best example). Once you get an object moving, it is going to take some outside force to change its motion. Adam and Jamie put this to the test recently when they explored the action movie standby of shaking someone off the roof of a moving car. They built a rig to do this safely, and then each took a turn on the outside of the car and in the driver’s seat. The results were perhaps what you would expect: Jamie couldn’t hold on to the roof for a series of swerves, a long turn, or a sudden stop, even from a mere 25 MPH. Adam’s tests were on the hood of the car, and though he did hold on for the straight-line stop, he was dislodged by the swerves and the long turn. Particularly when trying out the curving path, I was hoping to hear centripetal force mentioned (the force toward the center of a circle necessary to keep an object moving in a curved path) or at least inertia, but to no avail. This was another golden opportunity missed.
Finally, in the last episode of the most recent season, Grant, Tory and Kari tried to curve bullets as was done in the movie Wanted. Apparently this was the most-requested test on the MythBusters fan site in the last year. I saw the movie in the theater and decided against writing a column on it; I guess that was my missed opportunity. Angelina Jolie and the other superhuman assassins in the film could curve bullets simply by swinging their arms while firing, which—unsurprisingly—did not work for the MythBusters. Then, Tory carved grooves into the bullets and Kari removed the rifling from the barrel, so the bullets would not have the usual stabilizing spin. In the end, nothing they did altered the bullets’ path from a straight line. The tests were comprehensive and fun to watch, but could have gone one step further. The addition to the script of a sentence or two essentially saying, “This is exactly what we would expect, because in the absence of an outside force, objects continue to move in a straight line. This is one of Newton’s laws of motion,” would have made the episode far more useful to physics and physical science teachers.
While I have minor concerns with most episodes of MythBusters, I watch every episode and would use the show if I were still teaching high school physics. Middle school teachers could use some early episodes to bring up the isolation of variables. For example, Adam and Jamie’s explanation of the Diet Coke/Mentos reaction is the most complete I’ve seen; far better than the one on Food Detectives on the Food Network. They have done some excellent plant experiments as well: testing the effect of talking to plants, finding out if a rolling stone gathers moss, and comparing treatments supposed to keep a Christmas tree green as long as possible. Everyone on the show is clearly having fun while doing science—another valuable lesson students can take away from the show.
[updated 2009.07.08]
Jacob Clark Blickenstaff is Assistant Professor of Physics and Assistant Director of the Center for Science and Mathematics Education at the University of Southern Mississippi. He can be reached at jacob.blickenstaff@usm.edu.
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