The Thermodynamics of Menopause

Kellie’s hot flashes continue unabated, repeating every 45 minutes as they have done for the past three years. That’s like getting burned at the stake 35,000 times. Each attack turns her into a hot, sweaty mess. It's then quickly followed by a rapid drop in temperature that leaves her cold and clammy. Watching her repeated heating and cooling cycles got me wondering about the thermodynamics of a hot flash: how much heat energy gets released in each episode? It shouldn’t be too hard to calculate. We only need three pieces of information: the specific heat capacity for skin, the skin temperature change during a hot flash, and the mass of the flesh getting roasted.

Let’s start with the specific heat capacity for skin. For those of you who may not be familiar with the concept of specific heat, it’s the amount of energy per unit mass needed to raise the temperature of a material by one degree Celsius. A good value for the human body is 3,470 joules per kilogram-degrees Celsius. Don’t worry about those units for now. I’ll relate them to something more familiar later.

Next we need the skin's temperature change during a hot flash, which typically ranges from four to eight degrees Fahrenheit. Kellie’s hot flashes tend to be severe so we’ll use the higher value. And since we’re using the metric system we have to convert to Celsius, giving us a temperature rise of 4.4 degrees. It's like global warming only faster, and there's no chance of melting glaciers unless you send all women over 50 to Antarctica. 

Lastly, we need the mass of the flesh being heated, a delicate subject when talking about one’s wife. Kellie weighs between 130 and 135 pounds. I’m using the smaller number because I know what’s good for me.  We have to convert to the metric system so that gives us a body weight of about 60 kilograms. Since skin normally accounts for 12 to 15 percent of total body mass, that gives us 7 to 9 kilograms of skin. Gross! Unfortunately, we have to use the higher value because, as even Kellie would admit, baby got back (and some bodacious Ta-Ta’s too), and all that real estate requires a tad more skin.

Now all we have to do is multiply:

Heat = 3470 j/kg-C⁰ x 9 kg x 4.4 C⁰ = 137,412 joules

So now you’re probably asking, “What the (expletive) is a joule?” Rather than trying to explain joules, let’s convert it to something more familiar. According to Wikipedia, a stick of dynamite contains about one million joules of energy, and given Kellie’s firing rate, that means that over the last three years her body has exploded the equivalent of 4,809 sticks of dynamite. No wonder she’s been a bit irritable. Luckily, I know how to quench a fire. All she needs is a good hosing. She didn't seem too interested in my analysis. I guess she doesn't understand thermodynamics.
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