Myth: Ben Franklin discovered electricity by flying a kite in a thunderstorm and touching a key that had been charged up by lightning.
Building the kite
Kari, Grant and Tory wanted to build a kite to Franklin's specifications using period materials. The build team's initial materials and design was:
* Square frame of cedar
* Silk handkerchief for the kite material (precise size unknown, but handkerchiefs at that time were either 10"x10" or 3' x3', so they made one of each)
* Lightning rod
* Twine: they tested several twines from Franklin's time and chose the one with the best conductance.
Kari tested the big kite (3' x 3') and Grant tested the small kite (10" x 10"). Neither was successful in getting a kite flying. The only life shown by either kite was when the small kite made an attempt at Tory's crotch: "These kites are dangerous." -- Tory
After their failure with kites that followed Franklin's vague specifications precisely, Kari changed the designs to use more flexible dowels and a more typical diamond shape. The updated kite shape was able to get up in the air.
Three key myth tests
1. Key charge: could the charge from lightning have traveled from the kite, down the twine, to the key?
2. The spark: would the key have been capable of sparking to Franklin's finger?
3. Live or die: would Franklin have survived touching the spark?
Key charge test
They took the kite out onto the beach to test #1 and even setup a mock shelter on the beach as Franklin flew his kite through a window to stay dry.
Even though it was a clear, blue sky day, they knew that the kite should be able to build up static charge from the movement of the wind over the kite and the string. With a dry kite and string they were able to build up 10kV, which still wasn't enough to get a spark off the key. They then wet the string, which doubled the voltage and sped up the rate at which it charged up. This was still not enough to generate a spark off the key, but they were at least able to verify that the kite could build up charge: test 1 passed.
The spark test
The build team used Jamie's Van de Graaff generator to generate more voltage to see if they could get some sparks on the kite key. The Van de Graaff generator can generate 100,000 volts. They move the kite's lightning rod near the generator and were able to get tiny sparks off the key down at the other end of the kite string: test 2 passed.
The live or die test
For the final test, they built a Ben Franklin dummy with a torso and hands of ballistics gel and a skeleton of PVC pipe. They visited the PGE lightning strike test facility (previously seen in the showering during a thunderstorm myth). A heart monitor was rigged up to check whether or not 6mA of current crossed the heart (fatal).
Their initial setup stuck the kite right next to the generator as it slowly built up to the test charge of 480,000 volts. This was a bit too tough on their initial setup as the the kite string caught on fire before the full charge was reached. They changed things up so that the kite could be raised up to the generator when the fulll charge was ready.
With a wet kite string, there was a nice spark from the generator, to the kite, down the string, onto the key, and into the dummy Ben's finger. The heart monitor showed a lethal charge to Ben's heart. A real lightning bolt has a lot more charge, so it would be even less likely to survive: test 3 failed.
busted (the first two parts of Franklin's experiment are plausible -- flying a kite in a thunderstorm and having a charge travel down the string -- but it's unlikely that Franklin would have been able to touch the key)