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A short clip from Carl Sagan's Cosmos in which he explains how Eratosthenes measured the circumference of the Earth using shadows in two Egyptian cities. It is a clear, visual account of an ancient scientific feat.

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.

Isaac Arthur examines the Dark Forest theory, Cixin Liu's proposed solution to the Fermi Paradox in which civilizations stay silent and may destroy any that reveal themselves. He tests the theory's underlying assumptions and arguments.

David and Ben Crystal introduce the Original Pronunciation production of Shakespeare and show what it reveals about the history of English, including puns and rhymes lost in modern speech.

Mark Handley of UCL explains, with simulation visualizations, how early Starlink satellites without inter-satellite links could still give low-latency wide-area communication by hopping via ground relays. He shows it can beat fibre on many long paths.

Destin Sandlin of Smarter Every Day explores how grain bins work and the engineering and know-how involved in farming. His point is that farmers are exceptionally capable.

A 10-minute 3Blue1Brown chapter explaining the determinant as the factor by which a linear transformation scales area or volume. It builds the idea geometrically with animations before any formulas.

CGP Grey compares airplane boarding methods, based on an arXiv paper, and shows why the intuitive back-to-front approach is slow while random or outside-in boarding does better.

Practical Engineering explains why connecting solar and other inverter-based generation to the grid is hard. It covers grid stability, load balancing and the behind-the-scenes engineering challenges of renewables.

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.

The first episode of a Cities: Skylines series on urban politics and planning, focused on parking. It uses the game to show how parking minimums shape cities, drawing on Donald Shoup's book The High Cost of Free Parking.

Kurzgesagt compares how many people nuclear accidents have killed against other energy sources. It walks through the worst nuclear accidents and puts their death tolls in context per unit of energy.

Kurzgesagt explains stellar engines such as the Shkadov thruster and Caplan thruster, which could move the Sun and solar system across the galaxy over millions of years to avoid hazards and reach new regions.

Vox Earworm explains why John Coltrane's Giant Steps is so hard to improvise over: it is fast and moves through three keys. Musicians Braxton Cook and Adam Neely walk the host through the underlying music theory.

FortNine explains how Harley-Davidson ended up in decline, from a narrow lifestyle niche and an aging customer base to the pandemic hitting a company already in trouble.

Veritasium's Derek Muller visits NASA JPL to see the Mars helicopter Ingenuity before it was mounted on the rover. He explains how it can fly in Mars's thin atmosphere with large, fast-spinning contra-rotating rotors and low mass, and covers power and cold.

Guitarist Jim Lill methodically tests what in an electric guitar affects its tone, swapping parts on a partscaster and even trying a 2x4 body. He finds that wood and construction matter far less than people assume.

Real Engineering looks at why Africa's abundant solar potential is hard to turn into usable power, especially for Europe. It covers the transmission, infrastructure and economic obstacles, and the pivot from concentrated solar to photovoltaics.

Real Engineering explains why SpaceX is building Starlink, including the economics of satellite internet. It covers the latency advantage of light in vacuum over fiber for long-distance links.

A Kurzgesagt animation walking through how a Mars base could be built and why it would be punishing, covering radiation, temperature extremes, toxic dust and the need for shielding.

Robert Miles explains reward modelling, in which an AI learns what humans want from their preference comparisons instead of a hand-written reward function. He walks through the 2017 paper on deep reinforcement learning from human preferences.

NASA's animated explanation of the Curiosity rover's Mars landing, which relied on a complex automated sequence taking about seven minutes. It features NASA engineers discussing the risks before the 2012 landing.

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.

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.

Veritasium tells how Kodak film was fogged by radioactive fallout from the first atomic tests, letting the company detect nuclear testing before anyone announced it. The video also covers the deal to keep it quiet and how fallout contaminated packaging.

Matt Parker of Stand-up Maths asks whether a country's reported land area accounts for hills and mountains, working through how surface area depends on the resolution of elevation data. It follows up on a question from a viewer and work by researchers who measured it.

Not Just Bikes looks at the tiny microcars such as the Canta seen around Amsterdam. It discusses how they serve people with mobility issues, can use bike paths under certain rules, and where they fit in a 21st century city.

Wendover Productions explains how the US military moves people and materiel worldwide, including prepositioned equipment, sealift and airlift. It shows the scale of the logistics system behind US force projection.

Kurzgesagt introduces the Fermi paradox: with so many stars and planets, why do we see no sign of aliens? It sets up the question and what it might imply for our own future. It is part 1 of 2.

Sabine Hossenfelder explains how her opinion on dark matter has shifted, weighing the evidence for and against it and the case for modified gravity. It runs through what dark matter is and why it has not been detected.

Kyle Hill explains what nuclear waste actually is and how it is stored, arguing that the problem was effectively solved decades ago. It covers solid shielded waste and deep geological storage.

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.

PBS Space Time explains the Standard Model Lagrangian, the single equation encapsulating the particle physics theory, and visualizes what its terms mean.

Matt Parker of Stand-up Maths demonstrates MENACE, Donald Michie's 1961 machine made of matchboxes that learns to play noughts and crosses through reinforcement. He builds and trains a physical version.

Real Engineering looks at why nuclear power plants are expensive and how their economics compare with fossil and renewable alternatives. It is based on a video from the Illinois Energy Professors.

Kurzgesagt explains black hole stars, a hypothesized kind of giant star with a black hole at its core that could be a route to early supermassive black holes.

Medlife Crisis examines why some elite endurance athletes die in their sleep, covering extremely slow heart rates and the effects of performance-enhancing drugs that thicken blood. It uses cyclist Marco Pantani as an example.

Asianometry examines why Japan's software industry has lagged despite its hardware strengths. It looks at dependence on US software and the low prestige of programming.

John Green explains why the US spends far more on health care than other countries, going through insurers, drug companies, hospitals and lawyers. He argues the causes are complicated rather than a simple blame game.

Not Just Bikes explains how an electric bakfiets (Dutch cargo bike) replaced the family car after a move back to Canada, saving thousands of dollars. It shows how much it can carry, including kids and groceries.