/  curiosity   /  The physics of spaghetti
Domestic care
Ferdinando Catalano - Miryadi Assistenza Familiare

by Ferdinando Catalano


Let’s start with a fact almost everyone knows: at sea level, water boils at a temperature of 100°C. But few people know how the boiling process actually works. Normally, at room temperature, only the molecules on the surface participate in evaporation, but when the water is heated, 100% of the water’s mass becomes involved in the phase transition from liquid to vapor. Once it has reached the boiling point, all of the heat from the stove only serves to continue and expedite the evaporation process: no matter how much more energy it is fed, the temperature will not increase past 100 °C. The opposite is also true: after water boils, decreasing the heat supplied will not decrease its temperature until it ceases to boil.
Thus wrote Benjamin Thompson, one of the founders of thermodynamics, in a 1799 essay in which he scientifically analyzed the cooking processes, amazed at how poorly understood they were even by cooks, who dealt with them every day:

“The process by which food is most commonly prepared for the table – boiling – is so familiar to anyone, and its effects so uniform, and seemingly so simple, that few, I believe, have taken the trouble to investigate how or how these effects are produced”

Even today, such a simple and routine act as boiling water for pasta is often the source of much confusion. How much water should be used? Should the pot be covered, or not? When should you put in the salt? Once the pasta is added, can you lower the heat? For now, we will focus on the temperature of the water, leaving the other mundane kitchen mysteries for another day.

To boil, or not to boil? That is the question

Many people think that in order to properly cook pasta, boiling water is a fundamental necessity. But Thompson believed that this was not precisely true. In fact, cooking food depends solely on the temperature it reaches, and has nothing to do with whether the water is boiling or not. As to why,Thompson explains:
“All the fuel that is used to boil it vigorously is wasted, without adding a single degree to the heat of the water, nor can it speed up or shorten the cooking process by even one second. This is because it is from the heat, from its intensity and its duration that the food is cooked, and not by the boiling of water that has no role in that operation.”.
The takeaway? Once the water boils, you can safely lower the heat and save your gas.


Some may already be aware of this, but I would also advise you to steer clear of spaghetti (and pasta in general) if you’re high in the mountains. Why? Because pasta manufacturers produce it to a set of generalized expectations: it is meant to be cooked at (approximately) 100°C for the given duration.
At high altitudes, however (we’re talking in the order of 2500 – 3000 meters above sea level), the atmospheric pressure is much lower than it is at sea level, which means that the water will boil before its temperature reaches 100°. This is because the water molecules, when subjected to less air pressure, break their molecular bonds more easily and spread out into a gas more quickly. Because the water temperature will be lower, the pasta’s cooking process will take longer than the normal 5-7 minutes prescribed by the manufacturer; if you try to cook it as directed, you’ll end up with an inedible glue.


Assistenza familiare - trattare gli spaghetti
Now go to the kitchen and grab a single piece of spaghetti. Grasp it by the ends and try to break it in half. No way! At a minimum, three pieces will be produced. You can try as much as you want, but it’s not a matter of luck or skill; you won’t succeed. Why?
The answer is very complicated and not even the great American physicist Richard Feynman – who won the Nobel Prize for Physics in 1965 – was able to fully understand the reason. Recently, after 80 years of studies, the prestigious Massachusetts Institute of Technology (MIT) in Boston has managed to unravel the mystery.
When bending the spaghetti, the very center is the expected breaking point. However, just before it snaps at the midpoint, bending waves propagate very quickly from there to other points of the spaghetti, which cause breaks. To test their results, I attempted the method outlined by MIT, and to my surprise, I succeeded

But how?

With a very firm grip, grasp the ends of the spaghetti between your thumb and forefinger, and twist the noodle before anything else. Now bend, it and voila: the spaghetti snaps neatly in half. If you fail, try again with more power. The secret lies in using enough strength for the twist.
Give it a try, and let me know if you’ve succeeded!

Ferdinando Catalano

Drawing by: Michela Frare

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