Video notes
Latest videos
Watch each video, then open its page for the math behind every number, the files and every source we used.
- Short · Oct 31, 2026How Does a Ceiling Fan Work? From Rope to MotorHow does a ceiling fan work?
- Short · Oct 30, 2026How Does a Borewell Pump Work? It Can't SuckWhy can't a pump suck water from deep underground?
- Short · Oct 29, 2026How Does a Washing Machine Work? Dirty Socks, a BucketHow does a washing machine spin water out of clothes?
- Short · Oct 28, 2026How Does a Refrigerator Work? Ice, Milk, Moving HeatHow does a refrigerator make things cold?
- Short · Oct 27, 2026How Does an Elevator Work? A Rope, a Tree, a PianoHow does an elevator work?
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- Short · Oct 27, 2026How Does a Well Find Water? (Borewell Explained)How does a well find water?
- Short · Oct 26, 2026How Does a Tower Crane Build Itself?How does a tower crane build itself?
- Short · Oct 25, 2026How Do They Build Underwater Tunnels?How do they build tunnels under the sea?
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- Short · Oct 19, 2026Do Satellites Collide in Space? Who Dodges, and Who Can'tYes, but rarely. We mapped 15,939 low-orbit satellites from CelesTrak's public list: most fly in a few height lanes. Trackers flag close passes, live satellites dodge (a Starlink dodge about every 76 seconds, our math), and in 2009 a dead one couldn't.
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- Short · Oct 17, 2026The Birthday Paradox: Why 23 People Is EnoughIn a room of just 23 people, there's a 50.73% chance that two share a birthday (our math, assuming 365 equally likely days). Why it feels wrong, the two presidents born on Nov 2, our million-room simulation, and every source.
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- Deep dive · Oct 15, 2026A hole through the Earth: our full simulationOur own fall simulation on two Earths: 42 min 10 s through a textbook Earth, 38 min 11 s through the real layered one. Plus where you'd come out from 10 US cities, Honolulu and Beijing, and the deepest hole ever dug, to scale.
- Short · Oct 14, 2026If Earth Was a Grain of Sand, How Big Would the Universe Be?Our scale model, 14 steps on one scale: the Sun is a softball, Betelgeuse a football field, the Milky Way half the real way to the Sun, and the universe we can see still about 7 light-years wide.
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- Short · Oct 14, 2026Is GPT-6 free? What OpenAI says, and our free-account testOpenAI says Free gets GPT-6 Luna. We asked a free ChatGPT account five everyday questions: 3 of 5 came back interactive. The five prompts included.
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- Short · Oct 12, 2026Super El Niño 2026: what it means for your winterOur chart of NOAA's own data: 2026 is the 4th El Niño since 1950 to pass +3.6°F (+2.0°C) on the classic index, and it got there earlier than 1982, 1997 or 2015.
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