negative ions

3Blue1Brown builds visual intuition for quaternions, showing how to think about this four-dimensional number system using stereographic projection and rotations in 3D space. It is part one of a two-part series with an interactive companion site.

Numberphile's James Grime introduces quaternions, a type of number beyond the complex numbers, building up from real and complex numbers and explaining why they are useful.

Mathologer uses continued fractions to show why the golden ratio is the most irrational number, comparing it with root 2, e and pi and pointing to where this shows up in nature.

The Thought Emporium tests so-called negative ion and anti-5G wellness products and finds they are radioactive, with some coated in powdered thorium.

Tom Scott explains phatic expressions such as hello, thank you and how are you, which carry social meaning rather than information, and why replies like no problem can seem rude to some people.

Extra Credits explains from a game developer's perspective why AAA games have stayed at $60 despite inflation, and how that pressure drives DLC, microtransactions and loot boxes.

Matt Parker on Numberphile explains the strange properties of spheres in higher dimensions, such as how they poke out of their bounding boxes. It uses Pythagoras to build intuition for 4D and beyond.

A PBS Space Time episode on how gravitational wave observations of a neutron star merger, GW170817, can limit the number of spacetime dimensions. It is based on a 2018 paper.

Kurzgesagt asks whether advanced civilizations could have existed on Earth in the deep past and left little evidence. It looks at time as a dimension for searching for alien civilizations and the limits of the geological record.

An Isaac Arthur episode on civilizations in the dark, post-stellar universe, including black hole farming, accretion disks and the Penrose process as energy sources.

Veritasium debunks common climate change myths in under seven minutes, with references to NASA and published research. Topics include CO2 sources, sea ice and 1970s predictions of cooling.

Robert Miles introduces the first of several videos on the paper 'Concrete Problems in AI Safety', focusing on how AI systems can cause accidental negative side effects. It explains the problem in accessible terms.

Engineering Explained compares the lifecycle emissions of keeping an old car with those of buying a new, more efficient one. It weighs manufacturing emissions against emissions from driving, and covers gas versus electric cars.

Engineering Explained compares the lifetime CO2 emissions of a Toyota RAV4 Prime plug-in hybrid with a Tesla Model Y, looking at break-even mileage and whether electric cars are worse for the environment.

The Thought Emporium follows up on his earlier video showing negative ion products are radioactive, reporting that Amazon pulled listings and companies shut down. He tests more radioactive quack products with a Geiger counter and cloud chamber.

Technology Connections spends 22 minutes on the humble can opener and what its design shows about products and why people don't know what to look for. It uses an everyday tool to draw broader lessons.

Everyday Astronaut's Tim Dodd runs an hour-long, data-driven analysis of what rockets actually emit and how that compares with airliners and other industries. It breaks down exhaust by propellant type, per-passenger and total emissions, and ways launches could be cleaner.

Engineering Explained works through whether electric cars are really worse for the environment than gasoline cars. It covers battery production emissions, the electricity mix used to charge, and how long an EV takes to break even on lifetime emissions.

An Isaac Arthur episode on civilizations in the far future, past the Black Hole Era. It covers iron stars, Boltzmann brains, reversible computing and the idea of reversing entropy.

Mark Handley of UCL looks at how SpaceX's November 2018 revisions to the Starlink constellation affect network behavior. The video visualizes the orbits and routing and estimates latencies, building on his earlier video and research paper.

AlphaPhoenix uses Monte Carlo simulation and annealing-style methods to draw North Carolina congressional district maps, both gerrymandered and fair. He focuses on the fascinating computational problem rather than the politics.

Engineering Explained examines new research suggesting corn ethanol in US gasoline may emit as much or more carbon than gasoline. It covers the Renewable Fuel Standard and why ethanol was assumed to be a green fuel.

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.

Kurzgesagt explains the black hole bomb and how far-future civilizations might extract energy from spinning black holes, including Dyson-sphere-style ideas.

Geoff Marshall explains a running gag about London Underground stair signs claiming that the climb equals 15 floors, regardless of how many steps there actually are.

Technology Connections explains how heat pumps work as reversed air conditioners and why they can deliver several times the heat of resistive heating per unit of energy. It also tackles common myths such as poor cold-weather performance.

Technology Connections takes apart a 1940s Sunbeam Radiant Control toaster. It senses the toast's own browning and lowers and raises it automatically using purely mechanical parts and no electronics.

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.

Technology Connections takes a long, detailed look at how a 1970s electromechanical pinball machine works, from relays to stepper motors and mechanical logic. It is the first part of a series.

A long Technology Connections video arguing that public understanding of renewable energy is distorted. It covers solar economics, land use compared with ethanol corn, and battery myths such as cobalt.

Technology Connections explains how the simple American drip coffee maker works, including the bimetal valve and bubble-pump heating, and compares the original Mr. Coffee with modern machines.

Technology Connections explains how dishwashers work and how to use them well, including detergent use, the prewash cycle and why pre-rinsing hurts. It follows his earlier dishwasher videos.

Technology Connections' hour-long guide to electric vehicles, covering costs, trade-offs and especially how little home charging power most drivers need.

Technology Connections explains the early history of analog color television, from the 1954 start of modern color broadcasting, and how shadow masks work in CRTs. It is the first in a series on how analog color TV works.

Technology Connections explains in 33 minutes why thermoelectric (Peltier) cooling is far less efficient than compressor-based refrigeration.

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.

Technology Connections explains what forced-air furnaces are, how they work and why they need electricity. He covers combustion, airflow and the parts of a modern furnace.

Technology Connections looks at why awnings disappeared from houses and how effective they are at cutting solar heat gain and cooling costs. It argues they are a simple, forgotten cooling technology.

Technology Connections explains why car turn signals appear to drift out of sync at stoplights and how thermal and other flasher designs work. It also covers how synchronization could be achieved.

Technology Connections explains how an ordinary tank water heater works, including twin-element designs, and why it is cleverer than it looks.