# How many calories do superheroes burn using their powers?

Like every other ten year old, I loved watching Dragon Ball Z. I loved the flying, the powering up, the blasting, the powering up, the punching, the powering up, and the eating. Yeah, the eating. Something about watching Goku put away ten times his body weight in food just made sense – he had to get the energy for all that flying and blasting somewhere, right?

Assuming this bit of ‘kid logic’ applies to every superhero, how much would they need to eat?

Superman

The greatest feat of exertion I’ve ever seen Superman perform was in Superman Returns. Frank Underwood attempted to grow a continent using crystal-magic, so over the course of 2 minutes of CGI Superman lifted it into space before falling back to earth himself. The physics was terrible, but it’s a comic book movie, not The Martian.

How much energy does this require? The rock looks to be about 10 km across, which is about the size of the asteroid that killed the dinosaurs, so I’ll use a mass of 1015 kg [1]. To both lift this rock and then push it into an orbit where it won’t fall back to earth would require about 1021 Joules of energy, which is better described in nuclear bombs than calories (10,000 Tsar Bombas!). If Superman is supposed to be like a solar battery, charging himself with the energy of the sun, he would have to sun bathe for 10 billion years (the lifetime of the sun!) in order to charge up for this feat.

The Flash

According to Wikipedia, the Flash is able to run at the speed of light. Again, comic book physics. If we take this at face value, it’s impossible because if you could accelerate the Flash with an infinite amount of energy, he’d only ever approach the speed of light, never reach it. Instead, ignoring relativity, suppose he ran at the speed of light for one second, covering a distance of 186,000 miles (which gets him around the earth about 7.5 times). Since an average man running burns about 100 calories per mile, he’d have to eat 10,000 chickens to get the calories for this run. Alternatively, if you have to burn 3500 calories to lose 1 lb, the Flash lost 5,300 lbs on his jog.

Dr Manhattan

Dr Manhattan is one of my favorite superheros because his ‘control of particles’ power is basically a blank check for magic under the guise of science. On multiple occasions we see him disintegrate objects, teleport himself and others, and rearrange dirt to build a massive crystalline clock-like citadel on Mars. I think that last one might be his most energetic exertion, though given how effortless this appeared to be I wouldn’t be surprised if he could do much much more.

Since his power is manipulating atoms, and we see him building that glass monstrosity, we know that he’s breaking and reforming a colossal number of silicate bonds. With some fair assumptions, like that he builds 100 tonnes of glass, and that he’s working with oxygen and silicon atoms whose binding energy is about 100 eV, then we know it took about 1014 Joules – approximately the energy released by the Hiroshima bomb. This is over 10 billion calories. It’s a good thing Dr Manhattan doesn’t have to eat, because all those calories could feed 20,000 people for a year.

image credit: Wikimedia Commons

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