Physics

Commenting on recent theoretical physics debates in New York City, Columbia mathematician Peter Woit writes at Not even Wrong about what happens when multiverse theory is just assumed to be true: At 7 pm the American Museum of Natural History will host the 2016 Asimov Debate, with this year the topic Is the Universe a Simulation?. You can watch a livestream at that site. I confess that if this were a few days earlier, I would be convinced it was definitely a joke. But, it seems not, that instead this “has become a serious line of theoretical and experimental investigation among physicists, astrophysicists, and philosophers” and that it’s a “provocative and revolutionary idea”. One thing this is not is new. Read More ›

From Nature: The original claim comes from the DAMA collaboration, whose detector sits in a laboratory deep under the Gran Sasso Massif, east of Rome. For more than a decade, it has reported overwhelming evidence1 for dark matter, an invisible substance thought to bind galaxies together through its gravitational attraction. The first of the new detectors to go online, in South Korea, is due to start taking data in a few weeks. The others will follow over the next few years in Spain, Australia and, again, Gran Sasso. All will use sodium iodide crystals to detect dark matter, which no full-scale experiment apart from DAMA’s has done previously. Scientists have substantial evidence that dark matter exists and is at least Read More ›

From physics prof Philip Moriarity at Symptoms of the Universe: I’m going to put this as bluntly as I can; it’s been niggling and nagging at me for quite a while and it’s about time I got it off my chest. When it comes to publishing research, I have to come clean: I’m a hypocrite. I spend quite some time railing about the deficiencies in the traditional publishing system, and all the while I’m bolstering that self-same system by my selection of the “appropriate” journals to target. Despite bemoaning the statistical illiteracy of academia’s reliance on nonsensical metrics like impact factors, and despite regularly venting my spleen during talks at conferences about the too-slow evolution of academic publishing towards a Read More ›

From ScienceDaily: For decades, physicists have been working on the theory that dark matter is light and therefore interacts weakly with ordinary matter. This means that the particles are capable of being produced in colliders. This theory’s dark particles are called weakly-interacting massive particles (WIMPs), and they are theorized to have been created in an inconceivably large number shortly after the birth of the universe 13.7 billion years ago. “But since no experiments have ever seen even a trace of a WIMP, it could be that we should look for a heavier dark particle that interacts only by gravity and thus would be impossible to detect directly,” says Martin Sloth. Sloth and his colleagues call their version of such a Read More ›

Again? From NOVA:Today, there is wide scientific consensus that black holes are real. Even though they can’t be observed directly—by definition, they give off no light—astronomers can infer their hidden presence by watching how stars, gas, and dust swirl and glow around them. But what if they’re wrong? Could something else—massive, dense, all-but-invisible—be concealed in the darkness? A telescope as big as the Earth could tell a black hole from an exotic imposter. While black holes have gone mainstream, a handful of researchers are investigating exotic ultra-compact stars that, they argue, would look exactly like black holes from afar. Well, almost exactly. Though their ideas have been around for many years, researchers are now putting them to the most stringent Read More ›

But not support for supersymmetry. So says New Scientist: 2016 could go down as the year when a new picture of nature’s fundamental workings was unveiled. The hopes spring from two “bumps” that have appeared independently, in the same place, in the latest data from the LHC’s two big detectors, ATLAS and CMS. They point to the existence of a particle that dwarfs even the Higgs boson, the giver-of-mass particle discovered at CERN in July 2012. (paywall) From the paywalled portion: Strangely, the only thing we probably can rule out is that the particle is what many theorists, including Ellis, would like it to be: a supersymmetric particle. Supersymmetry is a theory that plugs many holes in the standard model Read More ›

From Brendon Brewer at Quillette: I first encountered the second law as a teenager, while reading an issue of the fundamentalist Christian magazine Creation, given to me by my grandmother. Since the article’s author wanted to argue against biological evolution, it claimed that the second law of thermodynamics implies evolution is impossible. Its definition of the second law was that disorder always increases with time. At first glance, this does seem incompatible with evolution by natural selection, which can lead to more complex, “better designed” organisms over time.3 At the time, I thought it was unlikely that mainstream biology would flagrantly contradict mainstream physics, so I remained sceptical of this argument, even though I couldn’t understand the counterarguments I found Read More ›

Further to Gravitational waves reliably detected – Updated IV, from Sean Carroll at the Atlantic: Einstein’s gravitational waves rest on a genuinely radical idea. … Einstein’s general relativity is a theory of gravity. It says that spacetime can be curved, and we feel the effects of that curvature as the gravitational force. According to relativity, the speed of light puts an absolute limit on how fast influences can travel through space. The Andromeda galaxy is two and a half million light years away, so it would take at the very least five million years to send a signal there and get a response back. We’ve all heard about this speed-of-light barrier, which applies to gravitational waves just as much as Read More ›

From Sabine Hossenfelder interviewed by John Horgan at Scientific American (blgs): Horgan: I have reasons to resent Sabine Hossenfelder. 1: She has criticized my end-of-science thesis. 2: She’s a free-will denier. 3: Scientists who write for non-scientists make it harder for mere journalists to make a buck. In December, she lectured at a physics conference in Germany, and then she reported on the conference in Forbes. Come on, how can journalists compete with that? (Um, you could, for example, try reporting on the genuine upheaval taking place in evolutionary biology. But you’d lose all your remaining friends … So let’s get back to work. ) Horgan: Nice! You recently said on your blog: “The biggest task of science bloggers–like Peter Read More ›

Paper. (open access) From MIT: LIGO signal reveals first observation of two massive black holes colliding, proves Einstein right. Now for the first time, scientists in the LIGO Scientific Collaboration — with a prominent role played by researchers at MIT and Caltech — have directly observed the ripples of gravitational waves in an instrument on Earth. In so doing, they have again dramatically confirmed Einstein’s theory of general relativity and opened up a new way in which to view the universe. But there’s more: The scientists have also decoded the gravitational wave signal and determined its source. According to their calculations, the gravitational wave is the product of a collision between two massive black holes, 1.3 billion light years away Read More ›

From Hawking’s second Reith lecture: The tranny From BBC: It was therefore very important to determine whether information really was lost in black holes, or whether in principle, it could be recovered. Many scientists felt that information should not be lost, but no one could suggest a mechanism by which it could be preserved. The arguments went on for years. Finally, I found what I think is the answer. It depends on the idea of Richard Feynman, that there isn’t a single history, but many different possible histories, each with their own probability. In this case, there are two kinds of history. In one, there is a black hole, into which particles can fall, but in the other kind there Read More ›

Prof asks. From ScienceDaily: In a paper published in the journal Proceedings of the Royal Society A, Associate Professor Joan Vaccaro challenges the long-held presumption that time evolution — the incessant unfolding of the universe over time — is an elemental part of Nature. In the paper, entitled “Quantum asymmetry between time and space,” she suggests there may be a deeper origin due to a difference between the two directions of time: to the future and to the past. … According to the paper, an asymmetry exists between time and space in the sense that physical systems inevitably evolve over time whereas there is no corresponding ubiquitous translation over space. This asymmetry, long presumed to be elemental, is represented by Read More ›

Physicist Rob Sheldon writes to respond to the claim that Jupiter does not shield Earth: Kevin Grazier, PhD, at the NASA Jet Propulsion Laboratory in Pasadena, describes the study in which he simulated the evolution of tens of thousands of particles in the gaps between the jovian planets for up to 100 million years. Based on the results, Dr. Grazier concludes that the widely reported shield role attributed to Jupiter is incorrect. More. Sheldon notes, While I have the greatest respect for people who run tens of Newtonian mechanics simulations of 10,000 bodies for 100 million years, the models only give results that were programmed into the simulation. If, for example, tomorrow someone were to find that the magnetized solar Read More ›

At Aeon, we are asked to consider the “superfluid universe.” Physicist Sabine Hossenfelder offers: Quantum effects are not just subatomic: they can be expressed across galaxies, and solve the puzzle of dark matter Most of the matter in the Universe is invisible, composed of some substance that leaves no mark as it breezes through us – and through all of the detectors the scientists have created to catch it. But this dark matter might not consist of unseen particle clouds, as most theorists have assumed. Instead, it might be something even stranger: a superfluid that condensed to puddles billions of years ago, seeding the galaxies we observe today. This new proposal has vast implications for cosmology and physics. Superfluid dark matter Read More ›

One can’t get a photo of a black hole but, from Wired: But thanks to a new telescope, Tim Johannsen, an astrophysicist at the Perimeter Institute and the University of Waterloo in Ontario, Canada, may be able to get a black hole pic after all. A loophole in physics means he might be able to see not the black hole itself, but its shadow. And, no big deal, but that photo just might overturn Albert Einstein’s theory of general relativity. What’s the loophole? … when astronomers look at a black hole, what they expect to see is a ring of bright light—the accretion disk—surrounding a circle of nothingness. That circle of nothingness is the shadow. (The black hole itself is Read More ›