this post was submitted on 27 Jun 2025
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Fun fact: a gram of plutonium contains about 20 billion calories. Yum.
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
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.
Plutonium actually does combust^1^. Even worse, it's pyrophoric^2^. I couldn't easily find kcal/g though.
I did a little digging. The heat of decay (so plutonium 238 just sitting around, not burning) is about .48 kcal/hr per gram. So if we were able to convert that energy to ATP like we do carbohydrates, eating about 300g of plutonium would be like eating a twinkie (150kcal) every hour. In about 88 years the energy output of that plutonium would have reduced to about a half-twinkie per hour.
Assuming you need 2000 kcal per day to maintain weight, that’s only 83 kcal per hour needed. So, if you could survive eating it and actually utilize the energy generated, you’d be set for life on food after eating less than 300g. We’d have to come up with a dosing schedule or you’d have to work out pretty hard as a young person to keep from getting fat.
The heat of combustion for plutonium based on a very cursory search (take it with a grain of salt) is about 1 kcal/g. So assuming your body could oxidize it, you’d get a one-time burst of about 2 twinkies worth of energy immediately upon eating that 300g.
Equivalent-level of fun fact: 1 gram of hay contains that much calories too!
No wonder cows are so fat
And it goes straight to my hips. By which I mean the bone marrow in my pelvis.
Hey, sexy bone-marrow pelvis, shake them atomic gains!
(OK, but like, if I produced synthetic plutonium I would make the box look like a chocolate box. Those workers & engineers deserve to have a fun work environment, engage in some shenanigans, make an oopsie from time to time.)
These hips don't lie : you got cancer
Why the pelvis specifically? How did it get there? What were you doing with it?
If you eat just one bite you'll never have to eat again for the rest of your life!
This is a commonly quoted fun fact that is not really true. There are 2 different definitions of calorie. One means the absolute amount of energy in an object, the other means the bioavailable amount of energy that a human can extract from it using their digestive system.
So every physical object that exists has some amount of potential energy contained within it which we can express in calories, but that doesn't mean it has any bioavailable calories. For example glass has some significant amount of energy contained within it, but it has 0 bioavailable calories.
This "fun fact" mixes up the two definitions, making the statement meaningless.
(Nothing against you OP, this is a commonly repeated falsehood)
Thank you for the clarification. I wanted to go along with the joke of it looking “edible”, but context is appreciated :)
And, if I have to explain the joke: it's just E=mc² (the Einstein thing ... well, the Einstein's thing's approximation), the energy (E) is the same for all mass (m) since the c is a constant.
You get the same 21 billon kcal from 1g of apples as from 1g of plutonium.
And since it's usually well known humans do not devour mass into pure energy that might trigger ppls sense of humour.
Also "potential energy" phrase is weird in that context.
It is a different definition, but it's the same unit... it's also more like saying "that ball of yarn is 10 metres" - the ball itself isn't 10 metres long in any dimension, but the meaning is clear given the context, as it would if you said "it's 0.05 metres". By having two meanings distinguishable by context, it seems like two definitions to me.
(Different definition/pov of what is measured, yes, that is where the joke is.)
Hehe, look at this falsehood - there is no way this things can talk!
(However imho this is a more clear example of 'two different definitions' of the main concept/phrase inferentially mixed together for comedic effect, bcs words can explicitly have more than one meaning, and yes, usually you can tell from the context.)
collapsed inline media
This pic is def:
Which definition does full corn kernels fall into?