this post was submitted on 27 Jun 2025
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Science Memes

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[–] FiskFisk33@startrek.website 17 points 12 hours ago* (last edited 11 hours ago) (1 children)

Not dietal calories.

The calorie numbers we assign to food, measure how much energy our body extracts from them when eaten.

In this context, plutonium is closer to 0

If we instead want to measure the actual total physical energy content of materia, we would turn to E=mc^2, telling us that a gram of anything has about 20 million kcal, no matter if its plutonium or diet coke. which is a slightly less useful value on food labels :D

[–] atomicorange@lemmy.world 14 points 11 hours ago* (last edited 11 hours ago) (1 children)

Technically it measures how much you can heat up a known volume of water if you burn the food. We have no way of measuring how much of that energy released by combustion actually gets absorbed and translated to ATP in the body, but it’s the best estimation we have of the relative energy content of foods.

There’s some carbohydrates, proteins, and fats that our bodies don’t seem to convert to energy (or only partially convert) but still technically contain “calories” because they’re combustible. Sugar alcohols, fiber, etc.

Plutonium doesn’t combust, but it would heat up water in a calorimeter. Really the test method’s applicability kind of falls apart when you start testing undigestible materials.

[–] SapientLasagna@lemmy.ca 2 points 17 minutes ago (1 children)

Plutonium actually does combust^1^. Even worse, it's pyrophoric^2^. I couldn't easily find kcal/g though.