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Hyperacute Interdynamics

|< < Prev #3178 (December 8, 2025)

Title text: Our models fall apart where the three theories overlap; we're unable to predict what happens when a nanometer-sized squirrel eats a grapefruit with the mass of the sun.

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Explanation

This comic depicts Miss Lenhart teaching a class, which has been a recent recurring theme on xkcd. She describes the three pillars of physics, those being General relativity concerning very large objects, Quantum mechanics concerning very small objects, and Thermodynamics. In the comic, Miss Lenhart replaces Thermodynamics with the fictional Hyperacute Interdynamics, which specifically covers objects 10-30cm (~4" - ~12") in size and 200-700g (0.44lb - 1.54lb) in mass. A student points out that the concept of Hyperacute Interdynamics is quite limited.

The teacher responds by stating that this is made up for by the fact that it is apparently very accurate and precise, and gives examples of how it is able to perfect squirrels and grapefruit, two objects which both fit the necessary size and weight specifications. She also states that there are hopes to unify this system with the other two.

The title text takes the joke further, giving reason to Miss Lenhart's remark about unification. She comments that, under the current system, measurements which require elements from all three pillars are impossible. The example she gives is equally absurd as the concept of Hyperacute Interdynamics itself, stating that it is unknown when a nanometer-sized squirrel (covering Quantum Mechanics and Hyperacute Interdynamics) eats a grapefruit with the mass of the sun (once again covering Hyperacute Interdynamics as well as General Relativity). This scenario would never occur in real life, so it is unknown why scientists would be willing to pursue it.

There is an inaccuracy in the comic: the Eastern Gray Squirrel, which is the most prevalent squirrel in Massachusetts (where Randall lives), measures 16-20 inches (approx. 40-50 centimeters) on average when fully grown, meaning that a fully-grown squirrel would be too big for Hyperacute Interdynamics to apply.

Transcript

[Miss Lenhart is teaching Cueball and Jill in a classroom. Both students are sitting at desks and Jill can be seen taking notes.]

[Miss Lenhart is talking to her students]

Miss Lenhart: Modern physics rests on three main pillars:

general relativity, which describes very massive objects,

[A zoom on Miss Lenhart's face]

Miss Lenhart: Quantum Mechanics, which describes very small objects,

[The view zooms back out. Miss Lenhart can be seen in the center of the panel near the bottom.]

Miss Lenhart: and Hyperacute Interdynamics, which describes objects 10-30cm in size and 200-700g in mass.

[The panel zooms back into Miss Lenhart's head. She is in the bottom-right corner of the panel.]

Student (off-panel): That last one seems kind of limited.

Miss Lenhart:Yeah, but over it's domain it's really precise. Absolutely nails squirrels and grapefruit.

Miss Lenhart:Someday we hope to unify it with the other two.

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