The MythBusters The MythBusters

MythBusters Episode 157: President’s Challenge

Premier Date: December 8, 2010

President Obama appeared in this episode and challenged the MythBusters to revisit this controversial myth. (It was previously tested in Ancient Death Ray and Archimedes’ Death Ray and was busted both times.)

An army of 500 people holding mirrors can focus enough of the sun’s light to set a wooden ship on fire.

busted

Recalling their experience with previous experiments, Adam and Jamie knew that it would be extremely difficult to coordinate 500 people in focusing their mirrors on to a single spot. They set about trying to construct aiming systems to assist the shield bearers. While Jamie’s efforts with a gunsight system proved unsuccessful, Adam found that stretching a net across the front of the mirrors provided a usable visual guide for aiming the beams. After a test in the workshop with 12 pepole holding mirrors proved the feasibility of this method, 500 double-sided mirrors were delivered and the crew covered one side of each with bronze Mylar film to represent the Greek mirrors, leaving the other side a modern mirror finish.

In the full-scale test, 500 high school students stood in for the Greek soldiers trying to set a boat’s sails on fire, using first the bronze and then the modern mirrors. Both of these efforts failed, as did a third trial in which the boat was pulled close enough to the shore for Jamie (representing an invading captain on the boat) to throw tennis balls and hit the students. Though Adam and Jamie declared the myth busted, Jamie noted that the reflections from the mirrors were extremely distracting and had blinded him temporarily, and that this may have been Archimedes’ true intent in recommending their use in warfare.

A strong enough punch, directed down onto the hood of a moving SUV, can cause it to somersault into the air. (Based on a scene from the film Hellboy)

busted

The Build Team first did some tests to determine the amount of force needed on the hood in order to get the SUV’s front end to touch the ground. They found that a total of 5,000 pounds was required, so Tory built a giant fist from a steel cylinder, to be dropped from a crane to give that much force on impact. The first few tests revealed problems with positioning and timing of the drop to hit the hood; after they fine-tuned the system, they scored a solid hit but failed to flip the SUV.

Reverting to small-scale testing with a toy SUV, the team experimented with combinations of fist weight, vehicle speed, and center of gravity, but still could not get a flip. They declared the myth busted at this point, then attached a long lever to a full-sized SUV’s roof in order to move the impact force away from the front axle, which served as the fulcrum for the car after impact. Even with this modification, the rear end only lifted 45 degrees into the air and the car did not somersault forward.