hot ones

Huygens Optics shows through a laser interference experiment that the question of a photon's size is really about coherence length. It argues that photons exist as energy exchanges between radiation and matter, not as little particles in free space.

Huygens Optics shows how DIY photon sieves shape a laser's wave front, explaining how they differ from zone plates and how aperture count affects the focal point, with time-resolved visualizations of the diffraction.

Tom Scott explains for Computerphile why handling time and timezones in code is so hard, walking through a simple web app that computes how long ago something happened. It covers the quirks of timezones and calendars and ends in an exasperated rant.

An RSA Animate adaptation of a Dan Ariely lecture on dishonesty. It explores when ordinary people lie or cheat and how they rationalize small acts of dishonesty.

Half as Interesting explains why the Eiffel Tower's night-time lighting is under copyright, which makes publishing photos of it at night legally problematic.

Veritasium shows how Hilbert's infinite hotel can still run out of room, using infinite buses of guests. It explains the surprising answer in a short animated segment.

Branch Education's animated deep dive into ASML's EUV photolithography machine and how it prints nanometer-scale transistors onto chips. It covers the system's components and the process of chip manufacturing.

LGR looks at the 1988 Canon Xap Shot, a still video camera that records photos to a floppy disk as analog NTSC signal rather than digital data.

Veritasium asks people where a tree's mass comes from, then explains that most of a dry tree's mass originates from carbon dioxide in the air. It combines street interviews with a short explanation of photosynthesis.

Real Engineering explains how Zipline built a drone delivery network for medical supplies in Rwanda. It covers the fixed-wing drones, catapult launch, parachute drop and the logistics behind the service.

Andrew Huang explains the harmonic series, which he calls the foundation of almost all music. He builds the idea up step by step, with demonstrations of overtones and how harmonies derive from them.

Tom Scott explains why Britain historically has separate hot and cold taps rather than mixer taps, tracing it to how water was stored in tanks. He notes why the hot tap is not safe to drink from.

Sciencium examines the Mpemba effect, the claim that hot water freezes faster than cold water. It walks through experiments and a published paper questioning the effect.

LegalEagle analyzes Katko v. Briney, the Iowa case about a homeowner whose shotgun booby trap injured a burglar, and the limits on deadly force in defending property.

Vsauce explores whether people in past decades really looked older than people of the same age today, or whether photographic and cultural factors make them seem so. It draws on old photos, yearbooks and perception research.

Wendover Productions explains why drone delivery has not become the future once promised. It covers no-fly zones, costs and the difficulty of the final drop-off.

A short animated TED-Ed lesson in which two competing ice cream vendors on a beach illustrate why rival shops cluster together. It introduces game theory and the Nash equilibrium through the Hotelling model.

PBS Space Time explains what happens as you approach and cross a black hole's event horizon, using Penrose diagrams and light cones as the tool for understanding spacetime there.

Smarter Every Day uses high-speed and Schlieren photography to show how a whip crack is a supersonic shockwave formed at the tip. It references academic papers on whip physics.

PBS Space Time explains how spacetime geometry and light cones determine the order of events and what can cause what. It visualizes causality in special relativity.

An episode of Coding Secrets by Jon Burton on retro copy protection, in particular physically damaging a disk with a laser so copies fail. It explains how this defeated hackers and pirates.

A Two Minute Papers episode on NVIDIA's recurrent denoising autoencoder, which cleans up noisy Monte Carlo path-traced image sequences. It shows how a neural network can produce usable renders from very few samples.

A short explainer from Nat and Friends on where Google Earth's 3D imagery comes from, how it is stitched together, and how often it is updated. It describes aircraft carrying camera rigs and photogrammetry that turns the photos into 3D models.

Professor Brailsford of the University of Nottingham describes how the university set out to print its own mathematics exam papers in the 1980s. The story centers on getting a Mergenthaler Linotron 202 typesetter to work with their own software.

A five-minute CGP Grey explainer arguing that a phone is effectively an extension of your mind, and that any backdoor or master key into encrypted devices will inevitably be abused or leaked. It frames the encryption debate as locks that are either unbreakable or absent.

Veritasium shows what the world looks like through a UV camera. It covers how pigments absorb UV, how fluorescence works, and how UV imaging reveals sunscreen effectiveness and skin damage.

CGP Grey explains the mess of Daylight Saving Time, including its dubious energy savings and the odd cases like Arizona that opt out. It is a short, simple explainer.

A short Techquickie explainer on why laptop webcams are much worse than phone cameras. It covers sensor size, image processing, and the interface differences between laptops and phones, with input from a Logitech engineer.

Nature video showing MIT researchers flying the first plane with no moving parts, powered by an ion drive that creates an ionic wind from high-powered electrodes. The 5m-wide craft flies across a sports hall.

Every Frame a Painting analyzes how Jackie Chan stages action comedy, with nine principles such as starting from a disadvantage, using the environment, clear shots, and keeping action and reaction in the same frame.

Sabine Hossenfelder explains how close nuclear fusion really is to break-even, and why headlines about ITER and lab milestones are misleading. She distinguishes plasma gain (Q plasma) from whole-system gain (Q total) and shows the latter is still far below one.

A short animated simulation comparing how Multics and Unix were developed, showing why Unix's small composable programs and pipes gave it a efficiency advantage. It frames Unix as a moonshot achievable by a small team.

Tom Scott explains for Computerphile why electronic voting is a bad idea, arguing that paper ballots are transparent, auditable and hard to tamper with at scale. He covers why moving voting to phones, tablets or computers undermines trust and verifiability.

Mathologer examines how identities like 1+2+3+... = -1/12 arise in Ramanujan's work, starting from his 1913 letter to Hardy. The video explains the rules for summing infinite series and why such results are meaningful but not naive sums.

Veritasium traces analog computers from the Antikythera mechanism and Kelvin's tide-predicting machines to fire control and modern analog approaches. It explains how these machines computed continuously rather than digitally.

Mick West analyzes the Navy's Gimbal UFO video and gives four checkable observations suggesting it is an infrared glare that appears to rotate because the camera rotates while tracking. He argues the object is likely a hot craft hidden behind the glare.

A clip from the 1983 BBC series Fun to Imagine in which Richard Feynman explains heat as the jiggling of atoms and how we perceive it as hot and cold.

Veritasium explores planned obsolescence, from the Phoebus lightbulb cartel to printers and phones. It explains how companies deliberately shortened product lifetimes and why products aren't better.

Technology Connections explains why humidity matters and compares the main types of humidifiers, including evaporative and ultrasonic designs. It covers how and why you would add moisture to indoor air.

A video essay from Every Frame a Painting about Vancouver, a major film production city that almost never appears onscreen as itself. It shows clips of films and TV shot there that pass the city off as somewhere else.