explain xkcd:Sandbox

Welcome to the explain xkcd wiki!
We have an explanation for all 3187 xkcd comics, and only 51 (1.6%) are incomplete. Help us finish them!

Latest comic

Go to this comic explanation

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.

|< < Prev Random Explanation

Explanation

This is incomplete: This page was created BY A STAR WITH THE MASS OF A SQUIRREL. Don't remove this notice too soon. If you can fix this issue, edit the page!

Miss Lenhart is teaching a class, a recurring theme on xkcd. She correctly describes two of the three pillars of physics: general relativity, concerning very large objects, and quantum mechanics, concerning very small objects. The third pillar is thermodynamics, but she replaces this with the fictional hyperacute interdynamics, which supposedly specifically covers objects 10 – 30 cm (~4" – ~12") in size and 200 – 700 g (0.44 lb – 1.54 lb) in mass.

When a student points out that the application of hyperacute interdynamics is quite limited, Miss Lenhart responds by stating that this is made up for by the fact that it is apparently very accurate and precise, and states that it is able to perfectly describe squirrels and grapefruit, two objects which fit the necessary size and weight specifications (though see below). Her comment that there are hopes to unify this system with the other two reflects the efforts of physicists to unify general relativity with quantum mechanics, so far without success.

While there is no actual field called hyperacute interdynamics, there is one of mesoscopic physics, described as the study of materials of an "intermediate size". The upper end of mesoscopic physics studies objects whose length is measured in micrometers — much smaller and lighter than what hyperacute interdynamics would study, so the analogy is not perfect. On the other hand, it happens fairly frequently in science that two separate length scales may be studied by different fields with no overlap. In this situation, innovations are, in principle, possible by trying to fill in this gap. An example is that structural biology is concerned with proteins and protein-sized objects, while cell biology is concerned with organelles; experimental techniques for studying phenomena between these two scales were less well-established until the development, in the 2010s, of cryo-electron microscopy.

The title text extends the riff on unification, noting that, under the current system, measurements which require elements from all three pillars are impossible. The example given — when a nanometer-sized squirrel (suggesting an understanding of equivalence across both quantum mechanics and hyperacute interdynamics) eats a grapefruit with the mass of the Sun (similarly, general relativity meshing with hyperacute interdynamics) — would cover all three domains. Such objects are not known to occur in real life, so it is unknown how or why scientists would be trying to measure them. A black hole with the mass of the Sun would have a Schwarzschild radius of 2.95 km, so it would take some significant revisions to theory to accommodate a grapefruit-sized object with that mass, before even considering how a squirrel of that small size (but of more normal mass) could exist and eat the former object.

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 — outside the range of sizes given for hyperacute interdynamics to apply. It does, however, weigh between 400 and 600 grams — within the weight range. Whether hyperacute interdynamics would apply, then, would appear to depend on whether the 'and' in Miss Lenhart's statement is inclusive (a union of candidates from the two separately applicable ranges) or exclusive (only items within the intersection of both stipulations), though the title text suggests that the former is the more logical.

Individually, the head-and-body size and the tail size of the eastern gray squirrel are each within the hyperacute effective size (though potentially not mass). If they were modelled individually, or if the squirrel curled up, then they may become able to be effectively modelled by hyperacute interdynamics, even if the entire, stretched out squirrel cannot. This shows the absurdity of hyperacute physics, with such a strict cut-off making it easy for objects to enter and exit the hyperacute effective size. By contrast, relativity and quantum mechanics slowly become worse at describing reality as size increases/decreases.

Some squirrels, such as the Borneo black-banded squirrel do entirely fit into the hyperacute effective size and mass.

Transcript

[Miss Lenhart is teaching a classroom holding a finger up in front of the class. Two students can be seen sitting at desks in front of her, a Cueball like boy is on the first row and Jill, taking notes, is in the second row.]

Miss Lenhart: Modern physics rests on three main pillars:

General relativity, which describes very massive objects,

[Close up of Miss Lenhart.]

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

[In a frame-less panel the view zooms back out, but shows only Miss Lenhart.]

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

[The panel zooms back in to a close up of Miss Lenhart.]

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.

  Add comment        Create topic (use sparingly)       Refresh 

Discussion

Make changes, try things out, or just have fun with the wiki here! Just leave everything above the line alone, please.

---

This is a test. PoolloverNathan^{[stalk the blue seas]} 20:48, 16 March 2021 (UTC)

This is not. —While False (museum | talk | contributions | logs | rights | printable version | page information | what links there | related changes | Google search | current time: 20:40) 18:38, 17 November 2022 (UTC)

A foreign student asked me to help fight against his math teacher. That was unusual. He was in that class for just a couple of weeks. The teacher's phone number was sent to me. The student asked me to spam-call the teacher. 172.71.155.55 22:58, 18 September 2023 (UTC)

here i'm just messing around in html, ignore this

^furhhfghure _{guyrburgryhuyvfr} "rvhru"

interesting way of writing quotations xd

hmmm this one of putting "<p>" in a line break will come in handy for when i want it to start at the same place than the first line

Please beware that <p> on mediawiki also disables automatic paragraph breaks, so you need a closing </p> or you'll break automatic paragraph formatting for the rest of the page. Zmatt (talk) 22:06, 31 July 2024 (UTC)

edit: da hek did that "</div>" come from An user who has no account yet (talk) 14:14, 13 October 2023 (UTC)

hi uh its hard to get here. is this a reference to undocumented feature??? hmm... this is interesting.
108.162.241.216 02:05, 23 November 2023 (UTC)

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

	Soup

yum yum [citation needed]

Hiuiedeixgeyceiyedhcdiedcve {{trout}}

This is the leaderboard:

Last 7 days (Top 50)

Rank Score Pages Changes Username 1 5,671 5,648 5,786 DollarStoreBa'al 2 1,631 1,616 1,675 Victoria 3 22 18 22 TheusafBOT 4 13 4 25 Trimutius 5 10 7 10 R128 6 10 6 10 Utdtutyabthsc 7 7 4 7 Lp0 on fire 8 7 1 11 Sturmovik 9 7 1 9 SammyChips 10 6 3 6 Kivi Shapiro 11 6 4 5 BunsenH 12 6 3 5 Kynde 13 5 3 4 Headphones the stickman 14 4 4 4 KelOfTheStars! 15 4 1 3 Magtei 16 3 1 2 Fephisto 17 3 1 2 Paul 18 3 3 3 Batbrain55 19 3 1 2 Beechmere 20 3 1 2 Stephan Leeds 21 3 1 2 Logalex8369 22 3 1 2 Questioner 23 2 2 2 Theusaf 24 2 2 2 boB 25 2 2 2 ISaveXKCDpapers 26 2 2 2 Starnote 27 2 2 2 AgentMuffin 28 2 2 2 Qoiuoiuoiu 29 2 2 2 first last 30 1 1 1 Michael Valler 31 1 1 1 Cobl703 32 1 1 1 DKMell 33 1 1 1 David Garfield 34 1 1 1 Daniel Griscom 35 1 1 1 CalibansCreations 36 1 1 1 August Fuller 37 1 1 1 I’m gonna fix this 38 1 1 1 Heleatunda 39 1 1 1 XkUjlmoh 40 1 1 1 mister tinkles 41 1 1 1 Darth Vader 42 1 1 1 Planer28 43 1 1 1 Sean McDonough 44 1 1 1 Dosbears 45 1 1 1 Ictlogist 46 1 1 1 EpicRedhead13 47 1 1 1 Rory O’Kane 48 1 1 1 1234231587678 49 1 1 1 SqueakSquawk4

<a href=" [AT THE JULY 28TH MEETING][tab] "Cancel the meeting! Our cover is blown.">
        Add comment

Is this out of date? .

New here?

Last 7 days (Top 10)

Rank Score Pages Changes Username 1 5,671 5,648 5,786 DollarStoreBa'al 2 1,631 1,616 1,675 Victoria 3 22 18 22 TheusafBOT 4 13 4 25 Trimutius 5 10 7 10 R128 6 10 6 10 Utdtutyabthsc 7 7 4 7 Lp0 on fire 8 7 1 11 Sturmovik 9 7 1 9 SammyChips 10 6 4 5 BunsenH

Lots of people contribute to make this wiki a success. Many of the recent contributors, listed above, have just joined. You can do it too! Create your account here.

You can read a brief introduction about this wiki at explain xkcd. Feel free to sign up for an account and contribute to the wiki! We need explanations for comics, characters, themes and everything in between. If it is referenced in an xkcd web comic, it should be here.

• If you're new to wiki editing, see the explain xkcd:Editor FAQ for a specific guidance to this Wiki and the more general help on how to edit wiki pages. There's also a handy wikicode cheatsheet.

• Discussion about the wiki itself happens at the Community portal.

• You can browse the comics from List of all comics or by navigating the category tree at Category:Comics.

• There are incomplete explanations listed here. Feel free to help out by expanding them!

Rules

Don't be a jerk!

There are a lot of comics that don't have set-in-stone explanations; feel free to put multiple interpretations in the wiki page for each comic.

If you want to talk about a specific comic, use its discussion page.

Please only submit material directly related to (and helping everyone better understand) xkcd... and of course only submit material that can legally be posted (and freely edited). Off-topic or other inappropriate content is subject to removal or modification at admin discretion, and users who repeatedly post such content will be blocked.

If you need assistance from an admin, post a message to the Admin requests board.

Category:Root category