How many peanut butter sandwiches does it take to fuel a Hulk?

Superheroes make superheroes Things: They jump, hit things, run fast, and sometimes shoot rays out of their eyes. These activities require energy, just like normal human activities. Getting up in the morning costs energy. Running around costs energy. Running a mile requires even more energy — but not nearly as much as it would take to fly a human-powered helicopter for a minute. (Yes, that’s real.) All of that energy comes from food. If superheroes also get their energy from food, how much would they need to eat to perform their energetic moves?

In honor of the new Disney+ series, which launched on August 17th, I’m going to focus on the moves of the Hulk and She-Hulk. I think we can assume that the two get their energy from food. A new clip from the series shows the Hulk (Bruce Banner) telling She-Hulk (Jennifer Walters) that they can drink as much alcohol as they want because Hulks have such a high metabolism. This means that their energy comes from the food and not from some strange mechanism or source, like an extra dimension.

food energy

We measure the energy in food in calories. For example, the packaging of a single candy bar may state that a serving has 200 calories. (Here are some examples with exact values.)

But there’s a difference between the way nutritionists talk about calories and the way physicists talk. For physicists, a calorie is the amount of energy needed to heat 1 gram of water by 1 degree Celsius. But that’s not the same as a food calorie. Food labels actually list things related to kilocalorieswhich means the 200-calorie candy bar is really 200 times 1,000 calories, or 200,000 calories.

That is confusing. And let’s be honest, we physicists don’t like to use it that much either these units for energy. Instead, we often use joules, where 1 joule is the energy needed to push a distance of 1 meter with a force of 1 newton. It takes about 10 joules of energy to lift a textbook off the floor and place it on a table. A food calorie is approximately 4,184 joules.

But for this demonstration, I think it’s best if we form our own energy unit. Let’s call it PBJ – the peanut butter and jelly sandwich energy unit. This is the amount of energy you get from eating one of these sandwiches, which is about 380 food calories, or 1.59 million joules. With this PBJ device, I can calculate the energy cost of superhero moves in the form of sandwiches. I just think this will be fun.

Energy needed for nothing

Simply staying alive requires energy: to breathe, to pump blood, and even to blink your eyes. The amount of energy required is called the basal metabolic rate or BMR. A typical mortal human might have a BMR of around 1,500 to 2,000 calories per day. Converted to my preferred unit of energy, a person uses about 4 to 5 PBJs per day. (Your mileage may vary.)

A BMR reading depends on a person’s age, weight, and height — but the Hulk and She-Hulk aren’t normal-sized people, so they don’t have normal BMRs. Let’s find out their weights and heights.

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