Physics

You read the title right. Recently, some astronomers thought they had spotted an “exomoon,” a moon orbiting an exoplanet. There are, of course, bound to be some. But now Gizmodo introduces us to the concept of the moonmoon, a submoon orbiting a moon. One research team is taking on the possibility: The team’s short analysis found that small submoons, perhaps 10 kilometers in radius, could only survive around large moons (such as the ones we see in our Solar System) far away from the host planet, according to the paper published on the arXiv preprint server. Moons that are too close to their host planets or too small might lose their submoons to tidal forces from the planet—shredding the submoon Read More ›

The Standard Model of physics holds that electrons should be almost perfectly round. As it happens, The electron gets its shape from the way that positive and negative charges are distributed inside the particle. The best theory for how particles behave, called the standard model of particle physics, holds that the electron should keep its rotund figure almost perfectly. But some theories suggest that an entourage of hypothetical subatomic particles outside the electron could create a slight separation between the positive and negative charges, giving the electron a pear shape. Now, the Advanced Cold Molecule Electron Electric Dipole Moment, or ACME, search, based at Harvard University, has probed the electron’s EDM with the most precision ever — and still found Read More ›

Recent cosmic ray activity in Antartica is  provoking question and speculation: Physicists don’t know what it is exactly. But they do know it’s some sort of cosmic ray — a high-energy particle that’s blasted its way through space, into the Earth, and back out again. But the particles physicists know about — the collection of particles that make up what scientists call the Standard Model (SM) of particle physics — shouldn’t be able to do that. Sure, there are low-energy neutrinos that can pierce through miles upon miles of rock unaffected. But high-energy neutrinos, as well as other high-energy particles, have “large cross-sections.” That means that they’ll almost always crash into something soon after zipping into the Earth and never make it Read More ›

French physicist Louis de Broglie (1892-1987) hoped that quantum mechanics could be brought within the same frame as classical physics via pilot wave theory, which envisioned “concrete particles, always with definite locations, that are guided through space by real pilot waves.” Apparently not. But a series of bouncing-droplet findings since 2015 has crushed this dream. The results indicate that Couder’s most striking demonstration of quantum-like phenomena, back in 2006 — “the experiment that got me hooked on this problem,” the fluid dynamicist Paul Milewski said — was in error. Repeat runs of the experiment, called the “double-slit experiment,” have contradicted Couder’s initial results and revealed the double-slit experiment to be the breaking point of both the bouncing-droplet analogy and de Read More ›

Uniting gravitation with the other forces of nature still eludes us: What we have done recently is to discover a gap in the mathematics that led to the idea that black holes are totally bald. In 2016, Stephen, Andy and I found that black holes have an infinite collection of what we call “soft hair”. This discovery allows us to question the idea that black holes lead to a breakdown in the laws of physics. Stephen kept working with us up to the end of his life, and we have now published a paper that describes our current thoughts on the matter. In this paper, we describe a way of calculating the entropy of black holes. The entropy is basically Read More ›

From the Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences The world of quantum phenomena is full of paradoxes incomprehensible to human intuition and inexplicable to classical physics. This is the thesis we almost always hear when it comes to quantum mechanics. Here are some examples of phenomena that are commonly considered to be typically quantum: a single electron generating interference fringes behind two slits, as if it were passing through both at the same time; particles that are in different states at the same time, only to appear “magically” in one selected state at the moment of observation; measurements without interactions; erasing the past by means of a quantum eraser; or finally, nonlocality, which gives Read More ›

Rob Sheldon mentioned a story going the rounds earlier today, about whether dark energy was “even allowed.” Here’s the story, from ScienceDaily: In string theory, a paradigm shift could be imminent. In June, a team of string theorists from Harvard and Caltech published a conjecture which sounded revolutionary: String theory is said to be fundamentally incompatible with our current understanding of “dark energy” — but only with “dark energy” can we explain the accelerated expansion of our current universe. Timm Wrase of the Vienna University of Technology quickly realized something odd about this conjecture: it seemed to be incompatible with the existence of the Higgs particle. His calculations, which he carried out together with theorists from Columbia University in New Read More ›

Our physics color commentator Rob Sheldon, occasioned by the social sciences’ war on empirical fact and objectivity: — Duke University professor John Staddon’s Quillette article is particularly relevant in light of the recent 20-paper hoax on the “grievance studies” division of sociology. As John Ioannidis has observed, many areas of science are suffering from “non-reproducibility.” Nor is this limited to the areas of liberal arts and medicine. Sabine Hossenfelder’s book, Lost in Math: How Beauty Leads Physics Astray, details the “non-empirical” nature of the devolution in theoretical particle physics. Just today, I noticed a link to an article, “Is dark energy even allowed?” that details the theory wars between string theorists, dark energy theorists, and experimental particle physicists. It demonstrates that Read More ›

Quantum theory specifies that information is never lost but what happens to the information when a black hole vanishes? In the latest paper, Hawking (1942-2018) and his colleagues show how some information 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. They call this sheen of photons “soft hair”. Read More ›

One must hope that Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray, isn’t too worried about the people who criticize her: Let us leave aside for a moment that you have to skip half the book to not notice I question myself on every other page. Heck, if you ask me to sign the book, I’m afraid I’ll misspell my own name. I’m a walking-talking bag of self-doubt. Indeed that was the reason I ended up writing this book. … Needless to say, making a case against a community of some thousands of the biggest brains on the planet has not been conducive to my self-confidence. But I have tried to find a scientific reason for the Read More ›

According to astrophysicist Ethan Siegel: Personally, I don’t expect these direct detection attempts to be successful; we’re stabbing in the dark hoping we hit something, and there are little-to-no good reasons for dark matter to be in these ranges. But it’s what we could see, so we go for it. If we find it, Nobel Prizes and new physics discoveries for everyone, and if we don’t, we know a little more about where the new physics isn’t. But just as you shouldn’t fall for the hyper-sensationalized claims that dark matter has been directly detected, you shouldn’t fall for the ones that say “there’s no dark matter” because a direct detection experiment failed. We are after the most fundamental stuff in Read More ›

At Horizons EU we are told, “New efforts to figure out just how fast the universe has expanded since the Big Bang, a speed known as the Hubble constant, could upend current theories of physics , according to some scientists. If current theories were upended, who would know. Consider these stories from this month alone: Discover: Even the best dark matter theories “are crumbling” Is there a crisis in the physics of our time? The cat is back: Is quantum theory dead, alive, AND contradicting itself? “Perhaps physics has slipped into a post-empirical era…” That’s a lot of fundamental uncertainty, as opposed to the endless quibbles of any scholarly discipline. Ultimately, more accurate measurements would establish the correct value of Read More ›

Because the best theories have not identified dark matter after decades: Having been fooled once, scientists have to ask: Is dark matter the new ether? For decades, a few rogue scientists have stood hopefully at the edge of respectability, offering their theory called Modified Newtonian Dynamics, or MOND. Essentially, it says that physics doesn’t work as we know it at the largest scales. It says we’ve been drawing the wrong conclusions, and dark matter isn’t required to explain the universe. No one has managed to develop a theory of MOND that adequately explains the universe around us, but it occasionally gains converts simply because the competing theory of dark matter has a glaring flaw: we can’t find it. Perhaps we’re Read More ›

Did Carlo Rovelli, start a fashion for debunking time with The Order of Time? Here’s science writer Marcia Bartusiak, author of Dispatches from Planet 3, asking whether it is time to just get rid of time: You might say that quantum mechanics introduced a fuzziness into physics: You can pinpoint the precise position of a particle, but at a trade-off; its velocity cannot then be measured very well. Conversely, if you know how fast a particle is going, you won’t be able to know exactly where it is. Werner Heisenberg best summarized this strange and exotic situation with his famous uncertainty principle. But all this action, uncertain as it is, occurs on a fixed stage of space and time, a Read More ›

Better known as Big Bang cosmology, it is not very popular in some quarters: Developed in the 1960s and ’70s, the standard model has some sizable holes: It can’t explain dark matter — an ethereal substance so far detected only by its gravitational effects — or dark energy, a mysterious oomph that causes the cosmos to expand at an increasing rate. The theory also can’t explain why the universe is made mostly of matter, while antimatter is rare (SN: 9/2/17, p. 15). So physicists are on a quest to revamp particle physics by probing the standard model’s weak points. Major facilities like the Large Hadron Collider — the gargantuan accelerator located at CERN near Geneva — haven’t yet found where Read More ›