FROM THE STAFF ROOM

The blog.

Notes on focus, friction and forgetting — how the quizzes are built, and what actually makes knowledge stick.

LEARNING 5 min read

How a cell responds to a message from another cell it never physically touches

Cell signalling lets one cell change another cell's behaviour from a distance, using a chemical messenger and a receptor built specifically to recognise it.

#biology#cellbiology#signalling

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LEARNING 6 min read

How a cell copies a three-billion-letter book

DNA replication copies three billion base pairs with about one mistake per billion — and even that low error rate is doing more work than it looks like.

#biology#genetics#dna

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LEARNING 5 min read

For the first six weeks, a human embryo hasn't decided if it's male or female

A single gene switch tells the body which set of ducts to keep, and which to let regress.

#medicine#anatomy#embryology

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LEARNING 6 min read

Every decision your phone makes is a pile of true-false switches

Autocomplete, face unlock, this quiz question loading — all of it is the same primitive, repeated billions of times.

#engineering#digitallogic#booleanalgebra

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LEARNING 6 min read

Cancer isn't one disease growing out of control — it's your own cells winning a contest

A tumour is a lineage of cells that, one small advantage at a time, outcompeted everything around it.

#medicine#pathology#cancerbiology

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LEARNING 5 min read

The machine that turns spinning into electricity, and the one that turns electricity back into spinning

A generator and an electric motor rely on essentially the same electromagnetic principle running in opposite directions: a generator converts mechanical rotation into electrical current, while a motor converts electrical current back into mechanical rotation.

#engineering#electricalengineering#powersystemselectricalmachines

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LEARNING 5 min read

The sociologist's question about religion that has nothing to do with whether any of it is true

Sociology studies religion as a social institution: how it organises communities, transmits norms and provides shared ritual and meaning, a question entirely separate from whether any of a given religion's theological claims are actually correct.

#sociology#culture#religionasculturalinstitution

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LEARNING 5 min read

The same note played loud, soft, sharp or smooth is four different musical statements

A written note only fixes pitch and rhythm. Dynamics, how loud or soft, and articulation, how a note is attacked and connected to the next one, are where a performer's own interpretive choices actually live, turning the same notes into different statements.

#music#performance#dynamicsarticulationexpression

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LEARNING 5 min read

The question every product launch is secretly betting an answer to before asking a single customer

Every product launch embeds assumptions about what customers actually want, whether or not anyone wrote those assumptions down. Market research exists to test those assumptions against real customer behaviour before a company commits serious resources to them.

#business#marketing#marketresearchconsumerbehaviou

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LEARNING 5 min read

The answer to an integral that actually has infinitely many correct answers

An indefinite integral finds a whole family of antiderivative functions at once, not a single function, because adding any constant to an antiderivative doesn't change its derivative, which is why every indefinite integral carries a plus-C.

#mathematics#calculus#indefiniteintegralsantiderivat

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LEARNING 5 min read

The map in your head that isn't actually shaped like a map

A cognitive map is your internal mental representation of a familiar space, and it doesn't preserve real-world distance and angle the way a physical map does. It distorts, compresses and reorganises information around landmarks and familiar routes instead.

#psychology#cognitive#cognitivemaps

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LEARNING 5 min read

Capitalism isn't just an economy, to a sociologist it's an institution with its own rules

Economists mostly study capitalism as a system of prices, incentives and exchange. Sociologists study it as a social institution: a set of norms, roles and legitimating beliefs that people are socialised into and that shapes behaviour well beyond the market.

#sociology#institutions#capitalism

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LEARNING 5 min read

The species that can't simply walk to a cooler climate

As climate zones shift, many species could in principle track them by moving toward the poles or higher elevation. Species with poor dispersal ability, or nowhere left to move to, don't have that option, and climate change ecology studies exactly what happens to them.

#biology#ecology#climatechange

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LEARNING 5 min read

The bonding model where electrons belong to the whole molecule and not to any one atom

The simpler valence bond picture treats a chemical bond as an electron pair shared between two specific atoms. Molecular orbital theory instead treats electrons as belonging to the molecule as a whole, and it predicts things the simpler picture can't.

#chemistry#physicalchemistry#molecularorbitals

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LEARNING 5 min read

The force with gravity's exact shape, and a strength gravity could never match

Coulomb's law shares gravity's inverse-square shape, but the electric force is vastly stronger, which is why it dominates atoms while gravity dominates planets.

#physics#electromagnetism#coulombslaw

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LEARNING 5 min read

The conditioning that shapes behavior after it happens, not before

Operant conditioning shapes voluntary behaviour through what happens after it, rewarding or punishing an action to make it more or less likely next time.

#psychology#behavioralpsychology#operantconditioning

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LEARNING 5 min read

The literary form named after being new, that isn't nearly as old as you'd think

Epic poetry and drama go back thousands of years. The novel is a comparatively recent invention, and its name literally means new because it once genuinely was.

#literature#fiction#novel

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LEARNING 5 min read

The bacteria in your gut that are harmless there and dangerous almost anywhere else

Whether a microbe causes disease often depends less on the microbe itself than on where in the body it ends up.

#medicine#pathology#infectiousdisease

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LEARNING 5 min read

Why you can only really hold about four things in your head at once

Decades of research have revised working memory's capacity downward — from a magic number of seven to about four.

#psychology#cognitivepsychology#workingmemory

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LEARNING 5 min read

The painters who stopped mixing colour on the palette and started mixing it in your eye

Instead of blending paint before it touched the canvas, they placed pure colour side by side.

#art#painting#impressionism

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LEARNING 5 min read

How a cell turns a gene into a protein using a messenger that gets destroyed after one use

Your DNA never leaves the nucleus. Every protein starts with a disposable copy of one gene, read once, then broken down.

#biology#cellbiology#genetics

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ENGINEERING 6 min read

The button that replays an intro it can't see

The hero intro is seven CSS animations on a fixed timeline. The replay button doesn't know their names, their count, or their timing — it asks the browser for all of them.

#animation#reducedmotion#webanimations

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LEARNING 5 min read

The narrator who is lying to you on purpose

An unreliable narrator isn't a mistake the author made. It's a gap left on purpose, between what you're told and what happened.

#literature#fiction#narrativevoice

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PRODUCT 5 min read

The mascot that notices when you're skimming

He doesn't know what you're reading. He knows how fast the page moved under your thumb, and that turns out to say more than you'd think.

#design#interaction#scrolling

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PRODUCT 5 min read

The teacher who watches your cursor

His mood on the landing page isn't random — it's a distance calculation run on every mouse move, with a deliberate escape hatch for anyone who can't see it move at all.

#design#interaction#accessibility

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PRODUCT 5 min read

Why we chose quizzes over push-ups

Physical friction costs you the room. Cognitive friction costs you a few minutes and pays you back three facts you keep.

#friction#design#screentime

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LEARNING 7 min read

Spacing, streaks and the forgetting curve

How the question scheduler decides what Mr. Grummel asks next — and when he asks it again.

#spacedrepetition#memory#curriculum

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ENGINEERING 9 min read

Building a classroom that loads in 300ms

Notes on animating a teacher who has to appear twenty times a day without ever feeling slow.

#animation#reactnative#performance

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FOCUS 8 min read

The psychology of an unlock

Why a three-question gate changes behaviour more than a hard block — and where it stops working.

#habits#attention#psychology

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PRODUCT 4 min read

Writing questions a stranger can answer

Our editorial rules for question banks: one fact, one skill, no trick wording, no trivia for its own sake.

#writing#questions#quality

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LEARNING 5 min read

The accounting that a company's outside investors never actually get to see

Cost and managerial accounting produce detailed internal reports built for a company's own managers to make operating decisions with, unlike financial accounting's standardised statements, which exist specifically for outside investors and regulators.

#business#accounting#costaccountingmanagerialaccoun

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LEARNING 5 min read

The handful of mechanical parts that show up inside almost every machine ever built

Gears, bearings, springs, fasteners and shafts are called machine elements because nearly every mechanical machine, however different its purpose, is actually assembled from some combination of this same small, reusable set of standardised components.

#engineering#mechanicalengineering#machinedesignmechanicalelement

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LEARNING 5 min read

The difference between a rhythm that's correct and a rhythm that actually grooves

A rhythm can be played with mathematically exact timing and still feel stiff, while groove comes from small, deliberate deviations from that exact timing, placing certain notes slightly ahead of or behind the strict beat in a way listeners feel as momentum.

#music#composition#rhythmiccompositiongroove

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LEARNING 5 min read

The ethics question underneath all the other ethics questions

Metaethics doesn't ask which specific actions are right or wrong, it asks a more fundamental question first: whether moral claims can be objectively true at all, and if so, what actually makes them true, before any particular ethical theory can even get started.

#philosophy#ethics#metaethicsthenatureofmoralfact

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LEARNING 5 min read

The ethical debate over whether "wrong" means wrong everywhere or just wrong around here

Moral realism holds that at least some moral claims are objectively true regardless of what any culture or individual believes, while moral relativism holds that a moral claim's truth depends on the standards of the culture or individual making it, and the two views disagree about what moral disagreement itself even means.

#philosophy#ethics#moralrelativismvsmoralrealism

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LEARNING 5 min read

The two curves that quietly set the price of almost everything you buy

Supply and demand models a market as two opposing forces, buyers wanting more at lower prices and sellers offering more at higher prices, meeting at the single price and quantity where the amount buyers want to buy exactly equals the amount sellers want to sell.

#economics#microeconomics#supplydemand

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LEARNING 5 min read

The paint that dries in minutes and the paint that stays workable for days

Oil, acrylic, watercolour and gouache differ mainly in what actually binds their pigment together and how that binder behaves as it dries, and that single difference in drying time and reworkability shapes almost everything about how a painter working in each medium actually has to plan and paint.

#art#painting#paintmediaoilacrylicwatercolou

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LEARNING 5 min read

The single equation that links how fast, how tall and how often a wave actually is

A wave is described by its wavelength, frequency and amplitude, and the wave equation links wave speed to wavelength and frequency with one simple relationship, wave speed equals wavelength times frequency, that holds for sound, light and water waves alike, however different the underlying medium.

#physics#wavesoptics#wavepropertiesthewaveequation

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LEARNING 5 min read

The two forces whose crossing point is supposed to explain a whole economy

Aggregate demand totals everything a whole economy wants to spend at each overall price level, and aggregate supply totals everything the economy is willing to produce at each price level, and the model extends supply and demand from a single market to a country's entire output and price level at once.

#economics#macroeconomics#aggregatedemandaggregatesupply

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LEARNING 5 min read

The liquid tissue that spends its whole life moving and still counts as an organ

The cardiovascular system moves blood, itself a genuine connective tissue rather than simply a fluid, through a closed loop of vessels driven by the heart's pumping, and blood does real, distinct jobs at once, carrying oxygen and nutrients, removing waste, fighting infection and helping the body clot.

#biology#humanbiology#cardiovascularsystemblood

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LEARNING 5 min read

The reaction that's addition run backward: a molecule losing atoms instead of gaining them

Elimination reactions remove two atoms or groups from adjacent carbons and form a new double bond in their place, the structural opposite of an addition reaction, which breaks a double bond open and adds atoms on, and the same starting material can often be pushed toward either outcome depending on the conditions.

#chemistry#organicchemistry#eliminationreactions

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LEARNING 5 min read

The two decades when a quarter of the world's population stopped being colonies

Decolonisation saw dozens of former colonies across Asia and Africa gain formal independence within roughly two decades after the Second World War, driven by a combination of local independence movements, weakened colonial powers and a shifting international climate that made continued colonial rule far harder to sustain or justify.

#history#contemporaryhistory#decolonisationindependencemove

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LEARNING 5 min read

The counting numbers that came before negative numbers were even allowed to exist

Natural numbers, the counting numbers starting at one or zero depending on convention, form the most basic number system mathematics builds on, and every richer number system, integers, rationals, reals, was constructed later specifically to answer a question the natural numbers alone couldn't.

#mathematics#arithmetic#naturalnumbersampnumbersystems

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LEARNING 5 min read

The protocol that decides which of a thousand paths your data actually takes

A routing protocol lets network routers automatically share information about available paths and agree on the best route for data to actually travel, and different protocols like OSPF and BGP exist because routing inside one organisation's network and routing between separate, mutually distrustful networks are genuinely different problems.

#computerscience#networking#routingprotocolsospfbgp

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LEARNING 5 min read

The two wars the Cold War's two superpowers fought without ever fighting each other

The Korean War and the Vietnam War were both fought between communist and anti-communist forces backed respectively by the Soviet Union and China on one side and the United States on the other, and both became genuine proxy wars precisely because neither superpower was willing to risk direct nuclear confrontation with the other.

#history#contemporaryhistory#thekoreanampvietnamwars

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LEARNING 5 min read

The evolutionary mechanism that changes a population's genetics without any advantage at all

Natural selection isn't the only mechanism that changes a population's genetic makeup over time, genetic drift, random chance in which individuals happen to survive and reproduce, can shift allele frequencies with no relation to fitness whatsoever, and gene flow, individuals moving between populations and interbreeding, can introduce or remove genetic variation regardless of whether it helps anyone survive.

#biology#evolution#mechanismsofevolutiongeneticdr

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LEARNING 5 min read

The database family that gave up shared table structure to get something else instead

NoSQL databases deliberately give up the relational model's fixed, shared table structure, and in exchange get a data model chosen to fit a specific kind of problem instead, document databases store each record as a flexible, self-contained document, key-value stores retrieve data through nothing but a single lookup key, and graph databases represent relationships between records as the primary thing being stored, not an afterthought.

#computerscience#databases#nosqlmodelsdocumentkeyvaluegra

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Latest notes.

LEARNING 5 min read

How a cell responds to a message from another cell it never physically touches

LEARNING 6 min read

How a cell copies a three-billion-letter book

LEARNING 5 min read

For the first six weeks, a human embryo hasn't decided if it's male or female

LEARNING 6 min read

Every decision your phone makes is a pile of true-false switches

LEARNING 6 min read

Cancer isn't one disease growing out of control — it's your own cells winning a contest

LEARNING 5 min read

The machine that turns spinning into electricity, and the one that turns electricity back into spinning

LEARNING 5 min read

The sociologist's question about religion that has nothing to do with whether any of it is true

LEARNING 5 min read

The same note played loud, soft, sharp or smooth is four different musical statements

LEARNING 5 min read

The question every product launch is secretly betting an answer to before asking a single customer

LEARNING 5 min read

The answer to an integral that actually has infinitely many correct answers

LEARNING 5 min read

The map in your head that isn't actually shaped like a map

LEARNING 5 min read

Capitalism isn't just an economy, to a sociologist it's an institution with its own rules

LEARNING 5 min read

The species that can't simply walk to a cooler climate

LEARNING 5 min read

The bonding model where electrons belong to the whole molecule and not to any one atom

LEARNING 5 min read

The force with gravity's exact shape, and a strength gravity could never match

LEARNING 5 min read

The conditioning that shapes behavior after it happens, not before

LEARNING 5 min read

The literary form named after being new, that isn't nearly as old as you'd think

LEARNING 5 min read

The bacteria in your gut that are harmless there and dangerous almost anywhere else

LEARNING 5 min read

Why you can only really hold about four things in your head at once

LEARNING 5 min read

The painters who stopped mixing colour on the palette and started mixing it in your eye

LEARNING 5 min read

How a cell turns a gene into a protein using a messenger that gets destroyed after one use

ENGINEERING 6 min read

The button that replays an intro it can't see

LEARNING 5 min read

The narrator who is lying to you on purpose

PRODUCT 5 min read

The mascot that notices when you're skimming

PRODUCT 5 min read

The teacher who watches your cursor

PRODUCT 5 min read

Why we chose quizzes over push-ups

LEARNING 7 min read

Spacing, streaks and the forgetting curve

ENGINEERING 9 min read

Building a classroom that loads in 300ms

FOCUS 8 min read

The psychology of an unlock

PRODUCT 4 min read

Writing questions a stranger can answer

LEARNING 5 min read

The accounting that a company's outside investors never actually get to see

LEARNING 5 min read

The handful of mechanical parts that show up inside almost every machine ever built

LEARNING 5 min read

The difference between a rhythm that's correct and a rhythm that actually grooves

LEARNING 5 min read

The ethics question underneath all the other ethics questions

LEARNING 5 min read

The ethical debate over whether "wrong" means wrong everywhere or just wrong around here

LEARNING 5 min read

The two curves that quietly set the price of almost everything you buy

LEARNING 5 min read

The paint that dries in minutes and the paint that stays workable for days

LEARNING 5 min read

The single equation that links how fast, how tall and how often a wave actually is

LEARNING 5 min read

The two forces whose crossing point is supposed to explain a whole economy

LEARNING 5 min read

The liquid tissue that spends its whole life moving and still counts as an organ

LEARNING 5 min read

The reaction that's addition run backward: a molecule losing atoms instead of gaining them

LEARNING 5 min read

The two decades when a quarter of the world's population stopped being colonies

LEARNING 5 min read

The counting numbers that came before negative numbers were even allowed to exist

LEARNING 5 min read

The protocol that decides which of a thousand paths your data actually takes

LEARNING 5 min read

The two wars the Cold War's two superpowers fought without ever fighting each other

LEARNING 5 min read

The evolutionary mechanism that changes a population's genetics without any advantage at all

LEARNING 5 min read

The database family that gave up shared table structure to get something else instead