While it would be awesome for people to be able to live in space, a “weightless” environment poses some serious challenges. Humans function best on Earth’s surface, where they are affected by a constant gravitational force. Without it, there are well-known consequences of long-term exposure to microgravity, including bone mass loss and muscle atrophy. So […]
Read MoreMcDuff and Schlenk had been trying to figure out when they could fit a symplectic ellipsoid—an elongated blob—inside a ball. This type of problem, known as an embedding problem, is pretty easy in Euclidean geometry, where shapes don’t bend at all. It’s also straightforward in other subfields of geometry, where shapes can bend as much […]
Read MoreBut you don’t have to be a superhero to experience this kind of flight. If you have a set of carbon-fiber wings and four engines, you can fly like Yves Rossy, also known as “Jetman.” Flying Like a Rocket Photograph: Moviestore Collection/Alamy Illustration: Rhett Allain Iron Man doesn’t have wings. He doesn’t need them. Instead, […]
Read MorePutting a percentage on the likelihood of a nuclear disaster can feel icky—like you’re boiling down the immensity of human suffering into a spreadsheet. “I think what people dislike about this is that people are thinking about the unthinkable,” says Spieghalter. But confronting the unthinkable is unavoidable if we want to reduce the risk of […]
Read MoreA few minutes into a 2018 talk at the University of Michigan, Ian Tobasco picked up a large piece of paper and crumpled it into a seemingly disordered ball of chaos. He held it up for the audience to see, squeezed it for good measure, then spread it out again. “I get a wild mass […]
Read MoreIn addition, the second law of thermodynamics signifies the statistical nature of the universe. Its building blocks are not stars, planets, humans, or bacteria—they’re the atoms and molecules that make us up. You can think of the atoms in the universe as a deck of cards, constantly being shuffled and reshuffled. By the end of […]
Read MoreThere are a couple of things to notice. First, after the collision DART is moving backwards, because it bounced. Since velocity is a vector, that means that it will have a negative momentum in this one-dimensional example. Second, the kinetic energy equation deals with the square of the velocity. This means that even though DART […]
Read MoreNow, what if I move outside this sphere? It turns out that the gravitational field due to a spherical distribution produces the same gravitational field as if all the mass was concentrated into a single point at the center of the sphere. This is kind of nice, as it allows us to easily calculate the […]
Read MoreFor a decade now, many of the most impressive artificial intelligence systems have been taught using a huge inventory of labeled data. An image might be labeled “tabby cat” or “tiger cat,” for example, to “train” an artificial neural network to correctly distinguish a tabby from a tiger. The strategy has been both spectacularly successful […]
Read MoreIn a physics lab in Amsterdam, there’s a wheel that can spontaneously roll uphill by wiggling. This “odd wheel” looks simple: just six small motors linked together by plastic arms and rubber bands to form a ring about 6 inches in diameter. When the motors are powered on, it starts writhing, executing complicated squashing and […]
Read MoreReally, the only difference is that this is a downward-curving path with the center of this circular curve below the slide instead of above. (Once again, the gray C-shape represents the path of the rider on the slide and the circular trajectory of their body, and the dot is the center of the circle.) That […]
Read MoreI was first just reading about how MRIs have got really big magnets in them, and thinking: I know that the magnetic field extends out away from them. It can’t extend out forever, because when I drop my keys, they don’t go flying off to the nearest MRI. So the first question is: How far […]
Read MoreThe one thing that all human civilizations have in common is that they end. For 10,000 years or so, that’s been the common factor. You can make an argument that civilizations tend not to last very long once they get to a certain level of tech. When they get to the point where they would […]
Read MoreLet’s consider an example with an imaginary planet. In this solar system, the planet completes one orbit around its sun in 8.6 solar days, instead of 365 days, as the Earth does. (I’m using a shorter year because it magnifies the difference between solar and stellar days, so you can see it more easily.) Here […]
Read MoreOther Asian innovations, like paper and gunpowder, have a clear record of dissemination to Europe, with artifacts and record-keeping that trace their travel westward along routes of trade and conquest. Printing doesn’t have that kind of paper trail, says Valerie Hansen, a professor of Chinese history at Yale University. There is no evidence that European […]
Read MoreMost of the quantum fields that fill our universe have one, and only one, preferred state, in which they’ll remain for eternity. Most, but not all. True and False Vacuums In the 1970s, physicists came to appreciate the significance of a different class of quantum fields whose values prefer not to be zero, even on […]
Read MoreGamma rays from this supernova remnant have been seen by telescopes since 2007, but exceptionally energetic light wasn’t detected until 2020, when it was picked up by the HAWC Observatory in Mexico, piquing the interest of scientists hunting for galactic PeVatrons. When gamma rays reach our atmosphere, they can produce showers of charged particles that […]
Read MoreIn 1963, the mathematician Roy Kerr found a solution to Einstein’s equations that precisely described the spacetime outside what we now call a rotating black hole. (The term wouldn’t be coined for a few more years.) In the nearly six decades since his achievement, researchers have tried to show that these so-called Kerr black holes […]
Read MoreSuperheroes do superhero things: They jump, punch stuff, run fast, and sometimes shoot beams out of their eyes. These activities require energy, just like normal human activities. When you get up in the morning, that takes energy. Walking around takes energy. Running a mile requires even more energy—but not nearly as much as it would […]
Read MoreA hidden link between two seemingly unrelated particle collision outcomes shows a mysterious web of mathematical connections between disparate theories.
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