How it works, and why it has to. See a science post you want explained? Tag @thewholewhy. Every number sourced. Full episodes on YouTube.
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The Whole Why: one question per episode, answered all the way down. How a thing works, and why it has to work that way. Every number sourced.
Full episodes on YouTube: youtube.com/@thewholewhy
ALT The Whole Why logo, a drawing callout with a W above a question mark, beside the words: Not just how it works. Why it has to. One question per episode, answered all the way down. Every number sourced.
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F1's biggest wings of the year, and its least downforce. Welcome to Mexico City. The track is over 2,200 m up, where the air is about a fifth thinner. A wing shoves air up, so the air shoves the car down. A fifth less air, a fifth less push. Same wing. Just less air to lean on.
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That white film on chocolate isn't mold: it's the chocolate's own fat.
Even at room temperature, about a quarter of the fat in a chocolate bar is liquid. Warm it, cool it, and some of that fat ends up on the outside.
Why chocolate turns white:
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That 3 a.m. smoke alarm chirp isn't bad luck. Your house got colder. Every 40 s or so the alarm loads its battery and checks the voltage against a line. Cold sags a battery under load, and homes are coolest 2–6 a.m. A nearly flat battery dips under first. Your alarm didn't choose 3 a.m. The cold did.
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Why only one of your mirrors warns that objects are closer: In the US the driver's mirror must be flat. The passenger mirror may curve: about 3× the view, but a car 10 m back shows up a third the size, like one ~30 m back. A wider view costs you true size. The warning is the receipt.
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Turn up the heat on a blue firework, and it stops being blue.
Red and green get brighter. Blue washes out. One lab tested ten blue firework pellets: the brightest was barely 30 % pure blue.
Why blue fireworks can't take the heat:
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Every number is sourced in the YouTube description: youtu.be/_9JECk3D7o8
Also inside: what a gas stove's blue flame has in common with a firework's, how a trace of sodium turns a flame yellow, and why blue was the last colour anyone got right.
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December 2000, London's Millennium Bridge: with 156 people walking on one span, the deck barely moved. With 166, it began to sway.
Not a hundred more people. Ten.
Why ten more people made a bridge sway:
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If nothing sticks to non-stick, how does the coating stick to the pan?
Not glue. Rough metal, a primer that sorts itself, and a bake that fuses PTFE to PTFE.
Almost nothing sticks to it, except more of itself.
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This rocket is already moving. It hasn't left the pad, but seen from space it's doing about 400 metres a second, heading east.
The ground's push is about 4 % of the speed to orbit, and worth about a fifth of the payload.
Why rockets would rather launch east:
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Every number is sourced in the YouTube description: youtu.be/IfrL-lEZjPY
Also inside: why Florida was plan B, the one launch of 2025 that went mostly west, and why the space station is tilted 51.6°.
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Your microwave isn't tuned to water. If it were, it would scorch a thin skin on your dinner and leave the middle cold.
It runs at 2.45 GHz, about a quarter of the way up to water's peak. On purpose.
Why microwaves aren't tuned to water:
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Every number is sourced in the YouTube description: youtu.be/58vcVc5TAW4
Also inside: the 1946 order that gave the oven 2,450, two companies that wanted different numbers, a chocolate bar that measures the speed of light, and a radio telescope fooled by a kitchen microwave.
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Every plane window you've looked out of has round corners. That isn't styling.
Cut a hole in a sheet of metal and pull on it: the edge carries three times the load, however small the hole (flat-plate theory). Tight corners: far worse.
Why plane windows can't have corners:
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Every number is sourced in the YouTube description: youtu.be/wIku60dOGzU
Also inside: the water tank at Farnborough where a Comet was broken on purpose, the bolt hole near a roof cut-out where the Elba break-up most probably began, and why the best window shape is an upright oval, not a circle.
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There's a sliver of quartz in almost every watch, bending back and forth 32,768 times a second.
The usual reason given: that's too high to hear. But the first quartz watches ran at 8,192, well inside human hearing.
The real reason quartz watches use 32,768. Full episode:
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Every number is sourced in the YouTube description: youtu.be/7r54cW-aGow
Also inside: the 1927 quartz clock that needed a spinning motor to count, the watches that throw vibrations away on purpose, and the earliest written hearing story we could find (a 2012 Wikipedia edit).
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Every GPS satellite carries an atomic clock that is deliberately set wrong.
In orbit it would run 38 µs a day fast, and light covers 11 km in that time. So it's built to tick slow: 10.22999999543 MHz, not 10.23.
Why GPS only works because of Einstein. Full episode:
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Every number is sourced in the YouTube description: youtube.com/watch?v=Uhd3zoVx…
Also inside: the 1977 satellite launched with its relativity correction off, the spec clause that sets the offset, and why "GPS would drift 10 km a day" answers a different question.
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