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CGP Grey walks through the odd history and quirks of the US-Canada border, including how it was surveyed and its irregularities such as exclaves.

WonderWhy surveys complex international borders, including enclaves like Vatican City, San Marino and Lesotho, the enclave-within-enclave town of Baarle, and the India-Bangladesh Cooch Behar region.

A Vox Borders episode with Johnny Harris explaining how China is gradually erasing the line between mainland China and Hong Kong since the 1997 handover. It describes the one country, two systems arrangement and its expiration date.

3Blue1Brown walks through a very hard Putnam competition problem and its elegant solution, emphasizing the visual intuition and the thought process behind solving it.

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.

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

An animated map showing the borders and populations of European countries for every year since 400 BC. Vassal states and colonies are excluded from population counts.

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.

A short film from the Competitive Enterprise Institute adapting Leonard Read's 1958 essay I, Pencil, showing how no one person knows how to make a pencil and how many people cooperate without central planning.

A short CGP Grey explainer about how countries are defined, why recognition by others matters, and the oddities of places like Taiwan and Vatican City. It shows that statehood is partly a matter of diplomacy rather than fact.

Technology Connections praises a 1940s-50s Sunbeam toaster and explains what makes a toaster well designed, drawing on a vintage Sunbeam video.

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.

NFPA video in which wildfire researcher Jack Cohen explains that embers (firebrands), not the flame front, are the main cause of homes igniting in wildfires. He shows how landscaping and removing debris around the home reduce risk.

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.

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.

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.

Ben Felix explains how to compare renting and buying a home by looking at unrecoverable costs, and distills it into the 5% rule of thumb. It is framed for a Canadian audience but broadly applicable.

An RSA Animate video that illustrates a talk by geographer David Harvey on the crises of capitalism. It covers creative destruction, wage stagnation masked by credit, and the search for a more just economic order.

Vox explains the Berlin and Kay research showing that languages around the world tend to invent color words in the same order. It walks through the hierarchy and the debate around it.

PBS Space Time explains the Hubble constant tension, in which two precise, independent methods of measuring the universe's expansion rate disagree. It covers why this calls some standard cosmology into question.

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.

Kurzgesagt examines how AI-generated content is flooding the internet, from video and music to news and books. It looks at how this makes verifying what is real harder.

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.

PBS Space Time, together with It's Okay to be Smart and PBS Eons, asks how a universe drifting toward disorder produced something as complex as life. It presents the idea that the laws of physics, through thermodynamics, may actually favor the emergence of life.

Vsauce explores math through card tricks and big numbers, including an animation of how enormous 52 factorial, the number of deck orderings, really is.

Kurzgesagt's animated overview of human origins and the vast prehistory before recorded history. It covers how modern humans emerged and spread.

A Veritasium explainer on how the brain works and how we learn. It is inspired by Kahneman's Thinking, Fast and Slow and covers System 1 and System 2 thinking and why harder learning builds skill.

A Vox Borders explainer on Hong Kong's housing crisis, the least affordable market in the world, and the tiny cage homes and subdivided flats people squeeze into. It looks at why prices keep climbing and how land policy contributes.