light table

Veritasium explains why the one-way speed of light has never been measured, only the round-trip speed, since measuring it requires synchronized clocks that assume the answer. It explores the implications for relativity.

A PBS clip in which Richard Feynman explains the strange nature of light and electromagnetic radiation. He conveys how little of it we actually see and how radio waves are present everywhere.

An 8-minute explainer on the Lightning Network and how it relates to Segwit, Bitcoin and Litecoin. It covers how off-chain payment channels route payments to scale blockchain transactions.

Technology Connections complains about the harsh, overly blue color of modern LED Christmas lights and tries more fixes for them. It follows earlier videos by the same creator on holiday lighting.

Technology Connections explains how LED traffic lights, which do not melt snow, drew complaints and were blamed for accidents. He uses it to illustrate the 'but sometimes' fallacy against new technology.

Professor Mike Merrifield of Nottingham explains in a mostly uncut conversation why light travels slower in glass. He treats light as a wave and describes how the material's electrons produce secondary waves that combine to slow it.

PBS Space Time argues that the speed of light is better understood as the speed of causality, the universal limit on how fast cause and effect propagate. Light travels at that speed because it is massless, but the limit itself is a property of spacetime.

Technology Connections explains why single-hose portable air conditioners are inefficient and often a poor choice compared with window units. It details how the single hose pulls in warm outside air and wastes energy.

Mathologer shows how times table diagrams on a circle produce cardioids and other curves connected to the Mandelbrot set. He explains the patterns and links to a tool for making your own diagrams.

Fermilab's Don Lincoln explains why light travels slower in water and glass. He knocks down common wrong explanations such as absorption and re-emission, then gives the wave-mechanics reason tied to refractive index.

ScienceClic explains why nothing can go faster than light by treating motion through space and time together, so everything moves at the speed of light through spacetime. It uses animated visuals to cover relativity basics in 12 minutes.

Half as Interesting explains why airlines flew empty 'ghost flights' out of Heathrow to keep their landing slots under use-it-or-lose-it rules.

A BBC Earth clip from Super Powered Owls in which the team uses sensitive sound equipment to compare owl flight with other birds. It shows why owls fly almost silently.

Not Just Bikes explains how Dutch traffic lights use early detection, transit priority and conflict-free design to cut waiting. The aim is to move as many people as possible rather than as many cars.

Asianometry explains the EUV light source inside ASML's lithography machines, where lasers hit falling tin droplets twice to produce 13.5 nm light. It walks through the engineering of the droplet generator, the pre-pulse and main laser, and the plasma that results.

Wendover Productions explains why Boeing's efficient 787 beat Airbus's giant A380, contrasting hub-and-spoke with point-to-point routes. It covers the economics of long-haul flights.

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.

Numberphile's James Grime explains Cantor's result that some infinities are bigger than others, including why the reals outnumber the integers. It is a short, accessible introduction to countable and uncountable infinity.

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.

Astrophysicist David Kipping presents the halo drive, a proposed way to propel a starship to a good fraction of light speed by gaining energy from a black hole. The video is based on his peer-reviewed paper and explains why energy is the main obstacle to interstellar flight.

PBS Space Time examines the interstellar object 'Oumuamua and the popular theories about it, including the light-sail hypothesis. It argues that a natural rock is the likeliest explanation.

AVweb's Paul Bertorelli explains why general aviation has failed to replace leaded avgas, blaming industry inertia, bureaucratic delay and an exemption that removes the incentive. This is part one of two.

SuperfastMatt looks at how the Tesla Model S retracting door handles were redesigned over time, from many parts to a motor plus sensor, with a focus on engineering and reliability.

AVweb's Paul Bertorelli explains in part two of a series why general aviation has not replaced leaded avgas. He covers industry inertia, bureaucratic delays and the exemption that lets the industry keep using lead.

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.

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.

A PBS Space Time episode explaining why faster-than-light travel is equivalent to travelling back in time, using relativity and Minkowski diagrams for different observers.

Technology Connections explains why North American tail light rules, which allow red turn signals and flashing brake lights, make signals ambiguous. He argues for amber signals and cites studies showing a safety benefit.

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.

Matt Parker of Stand-up Maths explains single-pile Nim and the trick that wins it, using Dr NIM, a 1960s mechanical plastic computer that plays perfectly. He teaches the strategy so viewers can beat friends.

Kurzgesagt explores the idea that life might have arisen shortly after the Big Bang, when the whole universe was warm enough to be habitable. It discusses what that would mean for the origin and spread of life.

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.

Technology Connections explains how analog television produced moving images without computers, covering scanning, CRTs and standards like NTSC and PAL. It is part of a series on analog TV.

Scott Manley explains the plumbing of rocket engines, including pressure-fed, gas generator, expander and staged combustion cycles. He shows why more complex designs exist and what they gain.

PBS Space Time introduces Miguel Alcubierre's warp drive, explaining how spacetime itself could be warped rather than moving a ship through it, and whether it is physically possible.

Smarter Every Day shares a binaural audio recording of the SpaceX Falcon Heavy launch made by Trevor Mahlmann, with explanations of the sounds including the sonic booms of the landing boosters. It is meant to be heard with headphones.

Eager Space examines the practicality of putting data centers in orbit, walking through three scenarios with cost calculations and the launch cost reductions that would be required.

Scott Manley surveys the research on whether people can adapt to rotating artificial gravity, from early Soviet centrifuge tests to modern studies. He concludes it is an engineering problem and discusses Coriolis effects and station radius.

Scott Manley explains the nuclear salt water rocket, Robert Zubrin's concept of a rocket fueled by a rapid nuclear reaction in uranium salt dissolved in water. He covers its extraordinary performance and the dangers of managing it.

Kurzgesagt explains the skyhook, a rotating cable with a counterweight that could catapult spacecraft from Earth orbit toward deep space. It covers why it would make space travel cheaper and more efficient.