ASPEN -- The Boeing Company is one of the many corporate sponsors of this year's Atlantic Ideas Fest in Aspen, and to swag satchel that all of us Fellows and presenters were given, Boeing added a hand crank flashlight.

Which got me to thinking: how many hand-cranked flashlights would it take to power to a single Boeing 737 on a cross-country flight? Or -- even just for a mile? The answer, based on some rough calculations, is -- 8,000,000 individual cranks. Electrical engineers -- I apologize in advance for this thought experiment.

Let's assume that the average flashlight consumes about 32,000 joules of energy in its lifetime from its two 9v batteries.

Now -- the Boeing swag flashlight -- let's call it the BSF -- has an LED bulb, which, according to most estimates, uses one tenth the energy of a standard bulb. I know that bulbs come in all different sizes, but let's just assume that the LED bulb on the BSF uses a tenth of the energy of a flashlight bulb. The bulb is powered by something called Faraday's Principle of Induction. Basically, the kinetic energy that we transfer from our hands to the flashlight moves a magnet which generates an electrical current. I think.

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The average Boeing 737-2 consumes about 736 gallons of fuel per hour, or about 91 gallons per passenger per hour during a trip from London to New York. Each airplane consumes about 175 megajoules per kilometer or about 245 megajoules per hour. Southwest Airlines had 445 B737s in service as of 2005; they flew 60,000,000,000 "revenue seat miles," which, if we divide by about 100 -- they filled about 70 percent of their seats -- or about 100 out of 135 -- is approximately six billion revenue seat miles in total. Six billion revenue seat miles multiplied by 175,000,000 joules = one quintillion and something joules.

So if we assume that Boeing's swag flashlights, with their fancy LEDs, last 50 times as long as the average battery flashlight at one tenth the energy, it would take about 65 billion persons continuously cranking to power Southwest's fleet for one year.

Or maybe we can simplify the calculation. One gallon of fuel powers a B737 airplane for about a fourth of a mile. One gallon of fuel is equivalent to 130,000,000 megajoules. If the energy expended by a hand crank is similar to that of a single footstep -- about 6.5 joules per second -- it would take approximately two million cranks of the flashlight to power an airplane for a fourth of a mile. I'm not knocking Boeing here; clearly, the company wants the Aspen lights to know that it is serious about improving the efficiency of its fleet. But let's keep this in perspective...

BTW: I'm keeping the flashlight. It's cool.

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