In 1920, the great Nikola Tesla patented this ingenious valve that allows fluid or gas to flow in one direction but not the other. And it does it based entirely on its geometry without any moving parts. Here is the US patent, number 1,329,559.

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This video captures a freight train engaging its emergency brake (about 2m in) and grinding slowly to a stop. Momentum is everything... until it's nothing. Read the rest

C4D4U's SOFTBODY TETRIS V16 is (as the name implies), the latest in a series of "softbody" simulations of Tetris, in which the tetronimoes are rubbery, jelly-like solids that glisten as they wobble into place. It's an incredibly soothing thing to watch (C4D4U calls them "ASMR for my eyes") and part of a wider genre of softbody sims. JWZ argues that this "becomes intolerable" upon the "realization that completed rows don't liquify" but if that's your thing, you need SOFTBODY TETRIS V9. Read the rest

This video depicts light speed in contexts where it appears to be slow. The moon is 1.2 light seconds from Earth; Mars several light minutes. This is, of course, why humans aren't moving out of this solar system any time soon. Read the rest

Sean Carroll is a physicist at JPL and the author of many popular, smart books about physics for a lay audience; his weekly Mindscape podcast is a treasure-trove of incredibly smart, fascinating discussions with people from a wide variety of backgrounds. Read the rest

Caltech theoretical physicist Sean Carroll, author of Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime, explains the concept of a "dimensions" at five different levels of complexity. Dr. Carroll sure has a big brane. Read the rest

Don't think his manager won't raise hell over their client working under these unsafe conditions. Read the rest

A favorite kitchen chemistry (and physics) experiment of kids (and adults), Ooblek is the weird result of mixing cornstarch with water. Now, MIT engineers have developed a mathematical model that can predict and simulate how the non-Newtonian fluid switches between liquid and solid depending on the pressure applied to it. From MIT News:

Aside from predicting what the stuff might do in the hands of toddlers, the new model can be useful in predicting how oobleck and other solutions of ultrafine particles might behave for military and industrial applications. Could an oobleck-like substance fill highway potholes and temporarily harden as a car drives over it? Or perhaps the slurry could pad the lining of bulletproof vests, morphing briefly into an added shield against sudden impacts. With the team’s new oobleck model, designers and engineers can start to explore such possibilities.

“It’s a simple material to make — you go to the grocery store, buy cornstarch, then turn on your faucet,” says Ken Kamrin, associate professor of mechanical engineering at MIT. “But it turns out the rules that govern how this material flows are very nuanced...”

Kamrin’s primary work focuses on characterizing the flow of granular material such as sand. Over the years, he’s developed a mathematical model that accurately predicts the flow of dry grains under a number of different conditions and environments. When (grad student Aaron) Baumgarten joined the group, the researchers started work on a model to describe how saturated wet sand moves. It was around this time that Kamrin and Baumgarten saw a scientific talk on oobleck.

Making a solar hot-dog oven is a science fair standby, but JohnW539's CNC-milled Sundogger Instructable really digs into the classroom portion, drawing on the creator's experience as a physics/astronomy/computer science prof at Middle Tennessee State University. Read the rest

Three basement levels of the Louvre are given over to the Centre de recherche et de restauration des musées de France (C2RMF), which provides research and restoration services to France's 1,200+ art museums and galleries. Read the rest

When I was very little, my big brother brought me in to school for show-and-tell. In the lunchroom, a kid fired a rubber band that hit me right in the face. I still remember the welt. This fascinating video uses high-speed footage to explain the physics behind this age-old form of weaponry. It also reminded me of the traumatic experience that forever made me a conscientious objector to the rubber band wars.

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In 1977, just a few months after Voyager 1 and 2 began their grand tour of the solar system, Carl Sagan gave the esteemed Christmas Lectures at the Royal Institution of Great Britain. You can watch them below via YouTube or at the Read the rest

Vantablack is a pigment made from carbon that is so black that anything painted with it looks like a hole in reality. It absorbs 99.965% of visible light. The Action Lab Man made something even blacker than Vantablack, then shines lights and lasers onto it to see if it visibly reflects the light. He uses marks made with a black Sharpie and a paint called Black 2 (which absorbs 95% of visible light) to compare how well his black square absorbs light. There's a surprising reveal at the end. Read the rest

The Action Lab Man demonstrates the physics of flowing air in several fun ways to explore Richard Feynman's "reverse sprinkler problem." A hypothetical reverse sprinkler (the sort that spins) is one that sucks in the fluid that surrounds it. Which direction does it turn? This question has led to lively debate among physics enthusiasts.

This question is also posed in a great physics puzzle book, called Thinking Physics. Read the rest

Stephen Hawking's final book, Brief Answers to the Big Questions, was released posthumously Tuesday by his children. Read the rest

Stephen Hawking's final paper that he and his colleagues completed just days before his death has now been published. It's titled "Black Hole Entropy and Soft Hair," co-authored with Sasha Haco, Malcolm J. Perry, and Andrew Strominger, about the black hole information paradox. Here is the abstract:

A set of infinitesimal VirasoroL⊗VirasoroR diffeomorphisms are presented which act non-trivially on the horizon of a generic Kerr black hole with spin J. The covariant phase space formalism provides a formula for the Virasoro charges as surface integrals on the horizon. Integrability and associativity of the charge algebra are shown to require the inclusion of `Wald-Zoupas' counterterms. A counterterm satisfying the known consistency requirement is constructed and yields central charges cL=cR=12J. Assuming the existence of a quantum Hilbert space on which these charges generate the symmetries, as well as the applicability of the Cardy formula, the central charges reproduce the macroscopic area-entropy law for generic Kerr black holes.

The Guardian has a translation:

In the latest paper, Hawking and his colleagues show how some information (contained in an object that falls into a black hole) at least may be preserved. Toss an object into a black hole and the black hole’s temperature ought to change. So too will a property called entropy, a measure of an object’s internal disorder, which rises the hotter it gets.

The physicists, including Sasha Haco at Cambridge and Andrew Strominger at Harvard, show that a black hole’s entropy may be recorded by photons that surround the black hole’s event horizon, the point at which light cannot escape the intense gravitational pull.

A metaphor for social media, courtesy of /u/imjustkidding on Reddit: "My breakfast sausages begged for their lives this morning. Listen to their cries for mercy." Read the rest