speed limits

Not Just Bikes explains how North American speed limits are set and why posted limits matter far less than street design. It argues that drivers follow the road's cues, so safe speeds have to be built into the street.

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.

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.

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.

Matt Parker analyzes the Minecraft speedrunning controversy in which Dream was accused of cheating via improbably lucky drops. He walks through the probability and the statistical arguments in the original accusation and the reply.

Thunderf00t presents high-speed camera footage of alkali metals such as sodium and NaK reacting with water. The footage shows that the explosion is not caused by hydrogen ignition, as the usual explanation says. It is a Coulomb explosion driven by electrons leaving the metal.

A Vox explainer on why California's high-speed rail project is years late and far over budget, with only a few concrete structures built by 2022. It covers the political, legal and routing challenges behind the delays.

Kurzgesagt explains why, even with science-fiction technology, most of the universe is permanently out of reach because of cosmic expansion and finite resources.

Matthias Wandel tests old and new code on a range of PCs, including a new mini PC, to measure how much faster modern hardware really is. He also shows optimization techniques such as branchless code, with benchmark programs on GitHub.

Veritasium explores why time seems to speed up as we age, covering chronoception and several competing explanations beyond the common proportional-theory argument.

Numberphile's Ben Sparks works through the physics of a car crash, showing how kinetic energy grows with the square of speed and why stopping distance climbs so quickly as velocity increases.

AlphaPhoenix uses a custom high-speed measurement setup to watch voltage waves travel down wires and split at a fork. It answers how electricity knows where to go and how quickly that process happens.

Wes Bos breaks down the techniques behind the McMaster-Carr website's speed: server-rendered HTML, prefetching, CDN and service worker caching, preloading, critical CSS and fixed-size images. He also notes its old-school jQuery and YUI JavaScript.

A Wendover Productions explainer on how China built the world's largest high-speed rail network so quickly and why its rail strategy differs from America's. It covers politics, social benefits and the economics of unprofitable lines.

Destin of Smarter Every Day films a cat falling in high-speed slow motion to show how cats right themselves in midair, and introduces the physics behind it.

PBS Infinite Series explains how Shor's algorithm lets a quantum computer break RSA encryption, building on earlier episodes about cryptography and the math of quantum computers. It works through the idea step by step.

Sabine Hossenfelder explains why she thinks faster-than-light travel may not be ruled out. She argues that the standard objections from special relativity are inconclusive.

A speedrunner-made explanation of the Super Mario World credits warp, an arbitrary code execution glitch that jumps the game straight to the ending. It simplifies the underlying assembly and memory behavior with animations so non-experts can follow.

Tom Scott visits Peachtree City, Georgia, which has about a hundred miles of dedicated golf cart paths that serve as an alternative to driving. He explains how the network works as a quasi-transit system that keeps cars off the roads.

Pannenkoek2012's commentated tool-assisted Super Mario 64 run collecting the Watch for Rolling Rocks star with half an A press, using parallel universes and QPU movement. The video is marked outdated in favor of a newer version.

Wendover Productions explains why US passenger rail lags behind other countries. It covers freight companies owning most of the track, geography and population density, and the economics of competing with flying.

Pannenkoek explains how Super Mario 64 handles wall, floor and ceiling collisions, including triangles, normal vectors, quarter steps and out of bounds. It is a detailed 37-minute technical walkthrough of the game's physics.

Linkus7 explains how a community reverse-engineered The Wind Waker to predict its random number generator and beat the Sploosh Kaboom battleship minigame consistently. It includes d3 animations by Peter Schmidt-Nielsen.

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.

Alex O'Connor shows that ChatGPT cannot draw a wine glass filled to the brim, and ties the failure to David Hume's missing shade of blue. It asks what the failure says about how image models learn.

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.

A 1937 GM-produced film explaining how the automobile differential lets wheels turn at different speeds around a corner. It uses clear animations and cutaway demonstrations to build the idea from first principles.

Veritasium's explainer on Godel's incompleteness theorems and the limits of mathematical proof, tracing set theory, Hilbert's program and the road to Turing and modern computing.

CGP Grey explains how traffic jams come from human driving behavior such as tailgating and reaction delays, and how leaving gaps and smoothing speed would reduce congestion. It also touches on self-driving cars.

Veritasium explains why analog computing may suit AI workloads, covering old analog computers, The Analog Thing and Mythic's analog chips that use flash memory for neural network inference. It argues digital hardware is hitting limits.

Cody's Lab builds a 200-billionth-scale model to show how far away the nearest stars are, using parallax and light speed. A short astronomy explainer on interstellar distances.

Practical Engineering explains pumped storage hydropower, which makes up most grid-scale electricity storage. It covers how it works and why it fits only certain geographies.

Real Engineering analyzes whether electric planes are feasible, focusing on battery energy density limits compared with jet fuel. It concludes electric flight works mainly for short ranges.

A Wendover Productions explainer on why train tickets, especially Amtrak in the US, cost so much compared with flying. It breaks down staffing, speed and the cost components behind a ticket.

Wendover Productions explains why modern airliners fly no faster than they did decades ago, covering the economics of speed and fuel efficiency, and why supersonic travel faded.

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.

An Isaac Arthur episode on arcologies, self-sufficient habitats that could house whole cities, on Earth or on harsh worlds. It covers how such structures might work and what limits their size.

MinutePhysics explains Shor's algorithm, showing how a quantum computer factors large integers by finding the period of a number modulo N. It walks through the modular arithmetic and number theory that give the exponential speedup over classical factoring, and why this threatens encryption.

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.

A short cartoon explaining how language models like ChatGPT work, from autocomplete and conditional probabilities to neural networks, gradient descent and backpropagation. It shows how networks act as universal function approximators.