Note: I'm using kilocalories for energy in this essay, because it's more intuitive that way.
The super soldier serum drastically increased Steve Rogers' metabolism speed, along with of course making him superhumanly strong with bullet-resistant skin. The MCU has stated that Rogers burns about 7650 (kilo)calories a day on average, burning more when exerting himself. With that in mind, here's a table:
Food | kcal/kg | kg/day to maintain mass |
Bananas | 890 | 8.6 |
Apples | 931 | 8.2 |
Whole wheat bread | 2830 | 2.7 |
Vanilla ice cream | 2070 | 3.7 |
Chocolate ice cream | 2160 | 3.5 |
Sources
Banana calories
Apple calories
Mass of an apple
Bread calories
Vanilla ice cream calories
Chocolate ice cream calories
More exertion
Sam Wilson implied that Steve ran 13 miles in 30 minutes (about 2:20 a mile, or 26 mph—similar to the top speed of the fastest sprinters).
A normal human who burns about 2200 kcal a day might burn 429 kcal running 10 min/mile for 30 min. If we scale that to Rogers' caloric needs, we get 1490 kcal, which is equivalent to about a pound of whole wheat bread. Alternately:
Which is pretty close to that result.
So, Captain America probably eats a lot. I don't know how to calculate his alcohol metabolization rate, but we can say that his protein intake would have to be pretty crazy too.
Cap's core temperature?
Using the Stefan-Boltzmann law, I can attempt to calculate Steve's body temperature.
First we need his total surface area. With this online calculator, a height of 6'2", and a weight of 240 lbs, we get 2.4 square meters.
Next let's convert his daily calorie burn to watts. 7650 kcal = ~32 megajoules. Over the course of 24 hours this is 370 watts.
Finally, we need a emissivity figure. Emissivity is the measure of how good a surface is at radiating energy as thermal radiation (usually infrared). What is the emissivity of human skin? It turns out to be an extremely good emissifier (?) with a emissification (?) value of 0.98. This is equal to water, and over thirty times greater than aluminum foil.
Plugging these values (2.4 m^2, 370W, 0.98) into the formula (actually, I used this calculator by Calctool, because I'm lazy) gives us...
Uh... that's far below the freezing point of water. According to this helpful chart, it's ~24 degrees below "Really damn cold".
Where did we go wrong?
Let's check normal human values in the calculator.
Yeah, it's clear there's a fundamental flaw in my method. And that flaw is...
Probably that I used a physics principle wrong? I'm not sure. It might have something to do with convection, exertion, or a simple misunderstanding of the underlying principles of the law.
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