light

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.

Technology Connections examines why light bulbs have the lifespans they do, including the real history of the Phoebus cartel. He shows that bulb life trades off against brightness and efficiency rather than being simple planned obsolescence.

Technology Connections explains why American cars all had the same standardized sealed-beam headlights until 1957. It covers the regulations behind the design and the effect on night visibility.

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.

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.

3Blue1Brown visualizes Feynman's lecture on the refractive index, explaining why light appears to slow down in glass and why the effect depends on color. It builds the idea from waves produced by oscillating charges in the material.

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.

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.

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.

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.

Musician and audio engineer Benn Jordan tries Dolby Atmos as a consumer, covering the theory of immersive audio, its business model, and home theater and headphone listening. He concludes it often falls short of the pitch.

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.

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 the proposal to use the Sun's gravity as a giant lens, sending a train of small light-sail spacecraft to the focal point roughly 550 AU out. It covers how such a telescope could image exoplanets in surprising detail and the engineering challenges involved.

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 examines why SpaceX, Google and others are looking at orbital data centers. He walks through the economics, heat rejection and solar power arguments, with links to the Lumen/Starcloud and Google Suncatcher papers.

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.

Explains the proposed NASA JPL plan to use the Sun as a gravitational lens, sending solar sail craft to its focal region to image an exoplanet's surface. It covers the distances involved, how imaging with the Sun would work and the mission design.

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.

Not Just Bikes explains how SUVs and light trucks have grown in size and share of US sales, and why that is dangerous for pedestrians, cyclists and city life. He covers the regulatory loopholes, such as fuel economy rules and the chicken tax, that favored them.

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.

Kurzgesagt lays out a speculative plan to terraform Venus, covering its hostile atmosphere and how it might be made Earth-like, with a sources page linked.

A minutephysics explainer showing that the Moon's path around the Sun is not a spiral but closer to a 12-sided polygon with curved corners. It argues the Moon arguably orbits the Sun rather than the Earth.

Breaking Taps explains how the cryogenic mirror actuators on the James Webb Space Telescope achieve nanometer precision using flexures. It shows a 3D-printed replica and how one motor handles both coarse and fine motion.

Scott Manley covers how GPS works and how civilian accuracy went from a planned 100 meters to about one meter. He explains the technology and the removal of restrictions that made this possible.

Real Engineering explains the engineering behind the James Webb Space Telescope, including its folding mirror, sunshield, orbit and cooling systems, and why deployment was so difficult.

Tim Dodd's hour-long deep dive on how rocket engines start, from solid motors to liquid engines. It covers thermal conditioning, spin-up, ignition methods, starting in space, and a step-by-step RS-25 startup.

Scott Manley looks at SpinLaunch, which aims to throw launch vehicles out of a spinning launcher at hypersonic speed. He covers its recent Mach 1 test of a one-third scale launcher and the engineering problems that remain.

Scott Manley explains the thermal balance of spacecraft and how a satellite could be configured to radiate away the heat from datacenter-scale computing in space. His rough numbers suggest it is feasible.

Scott Manley analyzes the idea of putting data centers in orbit, prompted by Lumen Orbit's funding. He examines the claimed advantage of constant solar power against launch cost, cooling and mass.

Branch Education explains how Starlink works, from the ground dish and satellites to phased-array beam steering and data routing. Animations cover how a beam stays connected to a satellite moving at 27,000 km/h.

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

A Veritasium video on the asteroid threat, with UCLA's Dave Jewitt explaining detection efforts and how different asteroid sizes compare in damage.

Joe Scott takes a serious look at space sunshades as a climate fix, asking how big they would need to be, what they would cost and whether they would work. He draws on Roger Angel's paper and launch options.

Astrophysicist Dr. Becky explains the Hubble tension, the disagreement between expansion-rate measurements from the cosmic microwave background and the distance ladder, and what early JWST Cepheid observations add.

A 105-minute technical deep dive from Noise In Space evaluating whether Starlink satellites could work as synthetic aperture radar. It covers SAR signal-to-noise, amplifiers, antennas, duplexing, phased array beamforming and simulations of V2 Mini and V3 satellites.

A Veritasium video touring Relativity Space and explaining why 3D printing whole rockets cuts tooling costs, allows rapid iteration, reduces part count and enables new designs. It includes an interview with Scott Manley on aerospace engineering.

CGP Grey explains why airport codes are inconsistent and sometimes confusing, from their origins in old weather station codes to the quirks that cause mistakes. He builds the story around a single typo that sent a flight to the wrong continent.

Huygens Optics explores the idea that space is a non-linear elastic medium, and uses simulations to show how wave energy might be confined locally into particle-like objects. It touches on inertia, the Schwinger limit and the vacuum as a medium.