Chris Russell wrote ...
I think the best argument to explain how this can't happen is to work through the math.
According to the information here:
Average mass of a popcorn kernel (at worst, site notes bigger kernels are more desirable): 0.133g
Average moisture content of a popcorn kernel at 21C: 15%, or .020g
Temperature at which a popcorn kernel pops: 250C (delta t of 229C)
We know that the heat of vaporization of water is 40.7kJ per mol, or 40.7kJ per 18.0g, or 2.26kJ per gram. This suggests that the energy required just to boil the water in one kernel of popcorn is roughly 45.2J. We also know that the energy required to heat a gram of water by 229C is 958J (4.184J per degree C), which adds another 19.2J to the required energy, upping the ante to 64.4J per kernel.
This means that your average 600W microwave oven should be able to pop 490 (65.1g) popcorn kernels, the amount in a single bag of Act II microwavable popcorn, in about 52.6 seconds. Note that this is assuming they absorb energy at 100% efficiency, there were no other ingredients to heat such as butter, no microwave energy was lost as heat while being reflected off the walls of the oven, no power dissipated by the magnetron due to impedance mismatch, and no heat lost from the kernels by convection. In reality we know that the real amount of time it takes is 2-3 times longer, but at least we know we are in the correct general area.
This also means that in order to be able to pop a kernel of popcorn in 13 seconds, as shown, the total power that those phones must deliver to a single kernel is a staggering 4.95W. Even allowing 2W per phone, this means that somehow an omnidirectional antenna is coupling 82.5% of its energy into a small kernel of popcorn some cm away. Laughable. But it gets worse.
A cell phone is not a microwave oven. There's no reflective cavity, so the microwaves only get to pass through the kernel of popcorn once, rather than many times. Therefore, in order to get as much energy as possible into such a small target, the beam would have to be incredibly tightly focused, well beyond what would be possible even with a well-designed parabolic dish.
Even if a cell phone was capable of emitting a maser-like 2W beam of microwave energy at 2.4 GHz that just happens to be exactly the width of a popcorn kernel, you will not see that sort of efficiency. The half power depth of for the heating of water at 2.45GHz is 12mm. Anything smaller than that will not even absorb half of the microwave energy that passes through it. A 6mm popcorn kernel (the largest size given here:
) would absorb about 30% of the energy that passes through it, if it were made of solid water. Since it's actually only 15% water, now it's only absorbing about 4.5% of the energy that passes through it, and I'm being very generous with the math here. For three phones to deliver that much power to *one* kernel, the phones need to emit a beam of microwaves 6mm wide, containing a total average power of 100W, or 33W per phone.
Folks, that is not a phone, that's a frickin' maser beam of death.
Cell phone can pop popcorn?
