Is A Hot Dog A Sandwich? April Fools Physics Paper Actually Has An Answer


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockApr 1 2022, 14:49 UTC
A soup, a salad, and... a sandwich? Image Credit: unterwegs/

A soup, a salad, and... a sandwich? Image Credit: unterwegs/

Physicists have the natural proclivity to reduce everything down to physics, especially when it comes to the big questions put forward by human thinkers. Why are we here? Is there life elsewhere in the universe? And, of course, is a hot dog a sandwich?

The answer is yes, according to a new paper. The work has delivered a new approach to culinary taxonomy based on the power of statistical mechanics.


According to the researchers, Madelyn Leembruggen and Caroline Martin, all food exists in this three-dimensional phase space, where it can be classified as soup, salad, or sandwich. Phase diagrams are often used in physics, for example, to explain the different phases of water depending on pressure, temperature, and volume.

The so-called Triple-S phase diagram for food taxonomy. Image Credit: Leembruggen and Martin. 2022

A mixture of ingredients in mostly water-based liquid is a soup. A mixture of ingredients with little water is a salad. This can be mapped on a graph in terms of temperature and pressure. Higher pressure leads to soup, lower pressure to salad, given how loosely it is kept together. However, low temperature and high pressure lead to what the physicists call glassy soup: ice cream. A plate of chicken wings or just shredded cheese is a salad (I'm totally going to use that claim). 

That is a single slice of the Triple-S phase diagram, where the carbohydrate content is at zero. Once you factor that in, then you need to explore the sandwich volume of this phase space. What’s brilliant (or maddening) is that carbs alone don’t make the sandwich – you need pressure and temperature too, plus multiple ingredients. A single raspberry or a steak exist outside of this diagram.


So, at high pressure, there’s no salad and you have things such as chicken noodle soup on the Soup side and soup dumplings on the sandwich side. But, as the temperature lowers, you find stuff like mochi on the sandwich side, and ice cream sandwiches on the boundary between soup (glassy) and sandwich.

Slices of the Triple-S phase diagram highlighting different food dishes. Image Credit: Leembruggen and Martin. 2022

At moderate pressure, you find pasta, found in soup, salad, and as a sandwich. So if you think that the hot dog being a sandwich is an affront to god, consider that most pasta dishes are salads unless stuffed. There, we also encounter a triple point. In standard phase diagrams, that’s where water for example exists both as gas, liquid, and solid. The triple point here is the ice cream sundae which is a soup, salad, and sandwich.

If you think this is all wrong, you are not alone. The researchers run a Twitter poll ahead of writing a paper and found that 78.6 percent of people disagreed with the classification. As it’s April Fools Day, they put a paper out on the ArXiv. 


If this one is not to your taste – sorry – maybe you’d prefer one on the effects of exomoons on werewolves or a machine learning algorithm that can predict winners of the Reality TV Dating Show The Bachelor.

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