ABCD
Disclaimer

You say no human would reply to a forum thread about Tom Bombadil by writing and editing hundreds of words of text, complete with formatting, fancy punctuation, and two separate uses of the word 'delve'. Unfortunately for both of us, you are wrong.
Snake-in-the-Box Problem

Chemistry grad students have been spotted trying to lure campus squirrels into laundry hampers in the hope that it sparks inspiration.
Grounded

We should have you at the gate in just under two hours--two and a half if we get pulled over.
Canon

Achilles was a mighty warrior, but his Achilles' heel was his heel.
Bad Map Projection: Interrupted Spheres

During the most recent glacial maximum, it's believed that land bridges extended from the surfaces and connected several of the spheres together.
Kite Incident

Detectives say the key to tracking down the source of the kites was a large wall map covered in thumbtacks and string. 'It's the first time that method has ever actually worked,' said a spokesperson.
Geologic Periods

Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.
Flettner Rotor

"And in maritime news, the Coast Guard is on the scene today after an apparent collision between two lighthouses."
iNaturalist Animals and Plants

Washington, DC: Eastern gray squirrel, Amur honeysuckle. Puerto Rico: Crested anole, sea grape. US as a whole: Mallard, eastern poison ivy.
Replication Crisis

Maybe encouraging the publication of null results isn't enough--maybe we need a journal devoted to publishing results the study authors find personally annoying.
Echo Chamber

This is almost as bad as the time I signed up for a purely partisan fishing expedition.
Unsolved Physics Problems

'Tin pest' makes more sense to me. Tin just doesn't want to be locked down in a shape like that. I get it. But why would any metal want to grow hair??
Building a Fire

That was quicker than usual! The cabin's sprinkler system often makes it really hard to keep anything lit.
Fix This Sign

We're building on our earlier success getting web developers to pay to change the backslashes in our displayed payment URL to forward slashes.
Geology Murder

After determining that his body was full of pipes carrying iron-rich fluid, our current theory is that the dagger-shaped object precipitated within the wound.
Artificial Gravity

Low gravity can cause bone loss, so we're pleased to report that, since we initiated capsule motion, the number of bones in each crew member has been steadily increasing.
Global Ranking

Starting a meta-leaderboard for tracking who holds the record for ranking behind the most distinct people on an online leaderboard.
Dehumidifier

It's important for devices to have internet connectivity so the manufacturer can patch remote exploits.
Laser Danger

To combat the threat, many airlines are installing wing-mounted spray bottles.
Weather Balloons

Once you add the balloons into the model, it makes forecasting easier overall--the forecast is always 'cold and dark, with minimal solar-driven convection.'
Farads

'This HAZMAT container contains radioactive material with activity of one becquerel.' 'So, like, a single banana slice?'
Interoperability

We're getting a lot of complaints from commuters who were routed onto a coaster, but the theme park patrons who spent hours stuck on an intercity line are also not happy.
Tukey

Numbers can be tricky. On the day of my 110th birthday, I'll be one day younger than John Tukey was on his.
Exoplanet System

Sure, this exoplanet we discovered may seem hostile to life, but our calculations suggest it's actually in the accretion disc's habitable zone.
Reading a Big Number
![[desperately] Maybe this is from some country where they use commas as decimal points, and also as digit separators after the decimal, and also use random other characters for decoration???](https://imgs.xkcd.com/comics/reading_a_big_number.png)
[desperately] Maybe this is from some country where they use commas as decimal points, and also as digit separators after the decimal, and also use random other characters for decoration???
Good Science

If you think curiosity without rigor is bad, you should see rigor without curiosity.
Alert Sound

With a good battery, the device can easily last for 5 or 10 years, although the walls probably won't.
Neighbor-Source Heat Pump

The installation of the pipes on the inside of the insulation can be challenging, especially when the neighbor could come home at any minute.
Trojan Horse

Ultimately, history would imperfectly record the story of the Foal of Troy.
Bridge Types

Pontoon bridges are just linear open-sided waterbeds.
Check Engine

They say it's probably safe to keep orbiting for a while, but if it stays on or starts flashing we might have to call someone.
Archaea

Under the two-domain system, anyone who punches you is technically an Archaean pathogen.
Mass Spec

Patients at least found it to be an improvement over Millikan's incredibly messy and unpleasant oil drop suspension procedure.
Drafting

A 5% efficiency gain at the cost of a 99% efficiency loss
Baker's Units

169 is a baker's gross.
Renormalization

Applying renormalization to bullies successfully transformed Pete & Pete's Endless Mike into Finite Mike.
Sail Physics

Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.
Modern

Scholars are still debating whether the current period is post-postmodern or neo-contemporary.
Deposition

P.S. If you have time travel, come to my birthday party Saturday!
Pascal's Law

Reductio ad absurdum fails when reality is absurd.
Globe Safety

Frankly, given their extreme gravitational fields and general instability, even 12-inch globes should probably be banned.
About 20 Pounds

In addition to gravity, burritos interact through the strong, weak, and electromagnetic forces, which is believed to be a major contributor to their popularity.
Unstoppable Force and Immovable Object

Unstoppable force-carrying particles can't interact with immovable matter by definition.
Jupiter Core

Juno mission data suggests that Jupiter actually contains Matryoshka doll-style nested copies of every other planet in the Solar System.
Chess Position

It's important to learn the moves that take you into the vortex, but it's best not to study vortex itself too closely. Even grandmasters who have built up a tolerance lose the ability to play for a few hours after studying it.
PhD Timeline

Rümeysa Öztürk was grabbed off the street in my town one month ago.
Tennis Balls

After initial tests created a series of large holes in the wall of the lab, the higher-power Scanning Tunneling Tennis Ball Microscope project was quickly shut down.
Air Fact

'Wow, that must be why you swallow so many of them per year!' 'No, that's spiders. You swallow WAY more ants.'
Anchor Bolts

The biggest expense was installing the mantle ducts to keep the carbonate-silicate cycle operating.
de Sitter

Our anti-de Sitter club is small at the moment, but I've started corresponding with the conformal field theory people.
The Roads Both Taken

When you worry that you're missing out on something by not making both choices simultaneously by quantum superposition, that's called phomo.
Anachronym Challenge

I have to pay with paper money.
Push Notifications

NOTIFICATION: Now dismissing a head of the Notification Hydra… NOTIFICATION: Success! You have dismissed a head of the Notification Hydra!
Tariffs
![[later] I don't get why our pizza slices have such terrible reviews; the geotextile-infused sauce gives the toppings incredible slope stability!](https://imgs.xkcd.com/comics/tariffs.png)
[later] I don't get why our pizza slices have such terrible reviews; the geotextile-infused sauce gives the toppings incredible slope stability!
Stargazing 4

We haven't actually seen a star fall in since we invented telescopes, but I have a list of ones I'm really hoping are next.
Decay Chain

If you have an old phone in a drawer, and you listen very carefully, you can occasionally hear the occasional tap of an emitted SIM card hitting the side of the drawer as the phone transmutes to a lower-end model.
Orogeny

Most properties can only boast INDOOR heated floors.
Terror Bird

There has long been debate about Big Bird's species, with some experts claiming he was a canary, but recent genetic analysis places him firmly in Cariamiformes.
Rock Identification

'Is it worth anything?' 'I dunno, is the answer to that question worth another $5?'
SawStart

Unfortunately, SawStart is one-use-only. Once started, the blade cannot be stopped, and must be replaced with a fresh blade while the running one is carefully disposed of.
Cosmic Distance Calibration

This is the biggest breakthrough since astronomers noticed that the little crosshairs around red giant stars starting to burn helium are all the same size.
Square Units

The biggest I've seen in a published source in the wild is an 80-fold error in a reported distance, which I think came from a series of at least three unit conversions and area/length misinterpretations.
Lungfish

I know having so many base pairs makes rebasing complicated, but you're in Bilateria, so shouldn't you at LEAST be better at using git head?
Planet Definitions

Under the 'has cleared its orbital neighborhood' and 'fuses hydrogen into helium' definitions, thanks to human activities Earth technically no longer qualifies as a planet but DOES count as a star.
Off By One

It does come at the small cost of a LOT more off-by-40-or-50 errors.
Water Balloons

Update: The physics department has recruited an astronomer who studies meteor fireballs.
Omniroll

It seems wrong that Fruit by the Foot is only sold by weight or by number of rolls.
Water Damage

Your homeowner's insurance might cover it, but be sure to check the subductible.
Tall Structures

Briefly set a new record for tallest human-made structure by getting my knit sweater snagged on the skydiving plane door as I jumped and not noticing until I'd landed.
Excusing Yourself

The most awkward part is when you have to pause to put on your shoes before you continue rolling out the door.
RNA

2040s: RNA formed the basis for life each of the five known times it arose on the early Earth.
Giants

I can't get over the suspicion that all those viral pictures are photoshopped and 'Flemish' belongs in the lower right circle.
Scream Cipher

AAAAAA A ÃA̧AȂA̦ ǍÅÂÃĀÁȂ AAAAAAA!
KM3NeT

Unfortunately, KM3NeT led to the discovery of the Pauli anglerfish, which emits Cherenkov radiation to prey on neutrino researchers.
Archive Request

They just want researchers in the enclosure to feel enriched and stimulated. ('The Enclosure' is what archivists call the shadowy world outside their archives in which so many people are trapped.)
Hardwood

They may technically have been softwoods at some point, but they definitely aren't now.
Atom

What's weirder is that muons turned out to be INCREDIBLY cute.
Incoming Asteroid

The bottom ones are also potentially bad news for any other planets in our solar system that have been counting on Earth having a stable orbit.
Suspension Bridge

As a first step, they can put in a secondary deck, to help drivers try it out and find out how fun the jumps are. After a while no one will use the old flat deck and they can remove it.
Rotary Tool

It was great until my thumb slipped and I accidentally launched my telescope into the air at Mach 8.
Stromatolites

If only my ancestors had been fortunate enough to marry into the branch of the bacteria family that could photosynthesize, like all my little green cousins here.
AlphaMove

It struggles a little with complex positions, like when there are an even number of moves and it has to round down, but when run against itself it's capable of finding some novelties. At one point I saw six knights on the board at once; Stockfish rarely exceeds four.
Humidifier Review

They should add a little sticker that certifies that the humidifier supports water conservation, but in the sense of energy conservation or momentum conservation.
Muons

Update: I've been banned from the physics department for the way I pronounce "Doppler effect."
T. Rex Evolution

Unfortunately, body size and bite force continue to increase.
Unit Circle

They're continuing to search for a square with the same area as the circle, as efforts to construct one have run into difficulties.
Chemical Formulas

Can you pass the nackle?
Human Altitude

I wonder what surviving human held the record before balloons (excluding edge cases like jumping gaps on a mountain bridge). Probably it was someone falling from a cliff into snow or water, but maybe it involved something weird like a gunpowder explosion or volcano.
Uncanceled Units

Speed limit c arcminutes^2 per steradian
Radon

A good ²³⁸Umbrella policy should cover it.
Chess Zoo

The zoo takes special care to keep kings separated from opposite-color pieces as part of their conservation program to prevent mating in captivity.
Trimix

You don't want the nitrogen percentage to be too high or you run the risk of eutrophication.
Features of Adulthood

I don't dig pit traps and cover them with sticks and a thin layer of leaves nearly as much as I expected; I find a chance to do it barely once a month.
Origami Black Hole

You may notice the first half of these instructions are similar to the instructions for a working nuclear fusion device. After the first few dozen steps, be sure to press down firmly and fold quickly to overcome fusion pressure.
Skew-T Log-P

The most important quantity for meteorologists is of course the product of latent pressure and temperostrophic enthalpy, though 'how nice the weather is' is a close second.
Time Capsule Instructions

Inside is a third box, labeled DO NOT OPEN UNLESS YOU ARE IN THE TIME ZONE WHERE YOU OPENED BOTH PREVIOUS BOXES.
Lasering Incidents

I still don't know how the police found my compound where I ran an illegal searchlight depot/covert blimp airfield/fireworks testing range.
Sun Avoidance

C'mon, ESA Solar Orbiter team, just give the Parker probe a LITTLE nudge at aphelion. Crash it into the sun. Fulfill the dream of Icarus. It is your destiny.
D Roll

Under some circumstances, if you throw a D8 and then a D12 at an enemy, thanks to the D8's greater pointiness you actually have to roll a D12 and D8 respectively to determine damage.
Exclusion Principle

Fermions are weird about each other in a standoffish way. Integer-spin particles are weird about each other in a 'stand uncomfortably close while talking' kind of way.