## Food Fables

This is going to ruin Thanksgiving forever.
Tori Bellacci

Lots of vacations and other distractions going on, so I’m going to try to catch up to the episodes I’ve missed, working backwards.  We’re starting with their Thanksgiving special!

I think my favorite part of this episode was not exactly part of the episode.  In between commercials for Megastorm and Sister Wives, Alton Brown explained how popcorn pops.  Explaining that the kernels were “steam bombs”, he painted a clear and interesting picture of the popping process.  It made me happy they included it and sad that it (and more like it) is not more thoroughly integrated into the episode.  For instance, a similar explanation of why eating a lot makes you tired from the nutrition professor would be a welcome addition.

I wish I could give more examples, but often it seems like the Mythbusters are allergic to large sample sizes.  When is the last time you’ve had identical scores on consecutive attempts at an arcade game?  It would have been extremely easy to have them play a few times and take the average.  I doubt the conclusions would have changed significantly, but they’d definitely have more of a case when they claim results are “conclusive”.

Now for my safety scolding on the heels of their cannon accident.  It will make me sound like an old grumpy man, but I don’t care. I know they’re professionals and escorted by a police car, but I’d really like to see seat belts on the guys as they’re driving around with their Thanksgiving dinner.  I hope/assume that they were wearing lap belts and the car was too old to have 3-seat belts.

It was great that they put thermocouples all over their car, and I loved the graphs.  I would have preferred to show some thermographic images as well:

However, they added a bunch of insulation after looking at all the results.  Wait, what?

For regions in equilibrium, the heat into a region equals heat out of the region.  Easy to say mathematically:

$Q_{in}=Q_{out}$

In the case of cooking in the car, $Q_{in}$ is the heat being generated by the relevant car part, and $Q_{out}$ is being lost either by convection to the surrounding air or conduction to an adjacent part.  For our purposes, the heat in is constant, but the heat out is proportional to the temperature difference between the region and its surroundings.

$Q_{out}=h(T_{region}-T_{exterior})$

The relationship is dictated by a heat transfer coefficient (in this case $h$, but sometimes $k$) based on the efficiency of either convection or conduction.  By adding the insulation, this transfer is inhibited, and the coefficient is decreased.  Thus, in order to maintain $Q_{in}=Q_{out}$, $T_{region}$ must increase.

That’s a mathematical way of saying what intuition already tells us: insulation will make the cooking regions hotter.  This is why I don’t understand why they didn’t add the insulation before measuring the temperature throughout the car.  Fortunately, this mistake was mitigated by leaving the thermocouples in and monitoring the temperature while cooking the dinner.

Finally, a last thought.  The episodes always begin with something to the effect of “Do not try any of the experiments you are about to see at home“.  While I understand this is something lawyers make them put in there, I’d appreciate them going all Mr. Wizard and giving us a few things to do at home.  With the exception of the Chinese popcorn cooker, I don’t see why most of the stuff couldn’t/shouldn’t be attempted at home.  Okay, maybe it’s a bad idea to have people hanging turkey parts from underneath their car in traffic, but why not give the audience something to do?  I understand they make their live show somewhat interactive…