01Money

A profitable company goes bust when customers pay slower than suppliers demand

Under accrual accounting, a sale counts as revenue when you deliver and invoice it, not when the money lands. So a builder can book a 300,000 job as profit in March while the client pays in July. Wages, rent and materials still fall due in April. Run out of cash and the business stops, whatever the profit line says. This is why the cash flow statement exists at all.

It is the single most common way a business that looks healthy on paper fails in practice.

02Tech

A touchscreen finds your finger because your body drains charge from a grid

Under the glass sit two layers of a transparent conductor, laid as fine strips crossing each other like graph paper. Each crossing holds a tiny electrical charge. Your finger is mostly salty water, which conducts, so bringing it close pulls some of that charge away and the chip notices which crossings dropped. No pressure is involved, which is why glass is no obstacle and a feather-light tap works. It also explains why a wool glove or a fingernail does nothing, and why water spilled on the screen produces ghost taps.

Explains every touchscreen frustration you have had, from gloves in winter to a phone going haywire in the rain.

03Science

Lightning hits the same spots constantly; that is why lightning rods work

Tall, isolated, conductive things get struck over and over. The Empire State Building is hit roughly twenty times a year, and lightning rods exist precisely because a strike point is predictable. Even a single flash usually contains several strokes racing down the same ionised channel within a fraction of a second, which is why lightning flickers. The saying is about luck, and it was never about physics.

Changes how you judge shelter in a storm: avoid the tall lone object, don't assume it is spent.

04Money

The oldest company answer, Kongō Gumi, stopped being independent in 2006

Kongō Gumi was founded in 578 in Osaka to build the Shitennō-ji Buddhist temple, and stayed in the same family for dozens of generations. Debt forced it to be absorbed in 2006, so it now trades as a subsidiary of another construction firm rather than on its own. Quizzes wanting a continuously independent business often accept Stora Enso, the Finnish-Swedish paper and packaging group, which traces its origins to shares in a Swedish copper mine recorded in 1288.

Superlatives about age depend on whether a business surviving inside a bigger owner still counts as itself.

05Science

The sky is blue because air scatters blue light everywhere

Sunlight is a mixture of all the colours. When it hits the molecules of the air, the shorter wavelengths at the blue end get knocked sideways far more than the long red ones, so blue light ends up bouncing at you from every part of the sky. It has nothing to do with reflecting the ocean, which is why the sky is just as blue over Kansas. At sunset the light crosses much more air, the blue is scattered out of your line of sight, and red is what reaches you.

One mechanism explains blue midday skies, red sunsets, and why the moon's airless sky is black.

06Ideas

Equal protection lets states classify people, but only with a reason

The Fourteenth Amendment, added in 1868 after the Civil War, says no state may deny any person the equal protection of the laws. That has never meant every law treats everyone identically. Laws sort people constantly: driving ages, tax brackets, licensing rules. The question courts ask is whether the sorting is justified, and they demand far more explanation for a line drawn by race than for one drawn by age. Note the word is person, not citizen, so it reaches noncitizens living in the state.

It reframes discrimination claims as a question about the government's reason, not about whether a rule feels unfair.

07Science

A microwave heats food by flipping its water molecules billions of times a second

Water molecules are lopsided, slightly positive at one end and negative at the other. The oven fills the box with radio waves at 2.45 gigahertz, and their electric field reverses billions of times a second, so the molecules keep twisting to face it. That jostling is heat. The waves only reach a couple of centimetres in, so the centre of a big dish warms by conduction from the outside, not from the inside out.

Explains why food comes out scalding at the edges and cold in the middle, and why stirring halfway helps.

08Health

Sugar does not make children hyperactive; controlled trials keep finding nothing

Studies that hide which drink has sugar in it, so neither parent nor child knows, find no change in children's behaviour. In one such experiment, parents told their child had just had sugar rated the child as more hyperactive, even though the drink was sugar-free. The real culprits are the settings sugar shows up in: birthday parties, Christmas, late nights, crowds of excited kids. Sugar still rots teeth. It just does not cause the bouncing.

Changes what you blame when a room full of children goes wild, and where you actually intervene.

09Science

Weather is Tuesday, climate is the average of thousands of Tuesdays

Weather is the specific report: rain, 14 degrees, wind from the west. Climate is the statistics of weather over a long stretch, commonly averaged over 30 years, including how often extremes show up. That is why one brutal cold snap tells you nothing about long term warming, and why forecasters lose accuracy after roughly a week while still saying useful things about the 2050s.

Most arguments about a hot week or a freak blizzard are really confusion between a single day and an average.

10Ideas

A constitution is the law that ordinary laws cannot break

Congress passes statutes, and the next Congress can undo them. The Constitution sits a level above that traffic. Article VI calls it the supreme law of the land, which means a statute that conflicts with it is void even if it passed with huge majorities and the public loves it. The document also does the plumbing: it creates Congress, the presidency and the courts, sets terms of office, and lists what each may do. A few thousand words, doing both jobs.

Everything else in constitutional law follows from this one ranking: some rules outrank the winners of the last election.

11Money

A balance sheet balances because everything a company owns was paid for by someone

Two claims exist on every asset. Lenders and suppliers have first claim, which is liabilities. Whatever is left over belongs to the owners, which is equity. So assets always equal liabilities plus equity, by construction rather than by luck. A bakery with 500,000 of ovens and stock, and a 400,000 loan, has 100,000 of equity. If the ovens lose value, equity absorbs the hit.

Once you see assets as claims, you can tell instantly how much of a business the owners really hold.

12Ideas

A million seconds is 12 days. A billion seconds is 32 years.

Count one number per second, never sleeping. You reach a million in under two weeks. You reach a billion around your thirty second birthday. Same words, wildly different objects: a billion is a thousand millions, not a bit more than one. This is why a person with a billion dollars is not a slightly richer millionaire, and why a billion pound overspend is not a rounding error on a million pound budget.

Politicians and headlines use million and billion in the same sentence, counting on you to feel them as neighbours.