Free Republic

Wigner sharpened the paradox by imagining a (human) friend of his shut in a lab, measuring a quantum system. He argued it was absurd to say his friend exists in a superposition of having seen and not seen a decay unless and until Wigner opens the lab door. [Nora] Tischler and her colleagues have carried out a version of the Wigner’s friend test. By combining the classic thought experiment with another quantum head-scratcher called entanglement—a phenomenon that links particles across vast distances—they have also derived a new theorem, which they claim puts the strongest constraints yet on the fundamental nature...

University of Chicago's Pritzker School of Molecular Engineering announced the discovery of a simple modification that allows quantum systems to stay operational—or "coherent"—10,000 times longer than before. Though the scientists tested their technique on a particular class of quantum systems called solid-state qubits, they think it should be applicable to many other kinds of quantum systems and could thus revolutionize quantum communication, computing and sensing. Quantum states need an extremely quiet, stable space to operate, as they are easily disturbed by background noise coming from vibrations, temperature changes or stray electromagnetic fields. Thus, scientists try to find ways to keep...

Scientists have produced the firmest evidence yet of so-called sterile neutrinos, mysterious particles that pass through matter without interacting with it at all. The first hints these elusive particles turned up decades ago. But after years of dedicated searches, scientists have been unable to find any other evidence for them, with many experiments contradicting those old results. These new results now leave scientists with two robust experiments that seem to demonstrate the existence of sterile neutrinos, even as other experiments continue to suggest sterile neutrinos don't exist at all. That means there's something strange happening in the universe that is...

Ron Cowen 3-22-2016 In tunnels deep inside a granite mountain at Daya Bay, a nuclear reactor facility some 55 kilometers from Hong Kong, sensitive detectors are hinting at the existence of a new form of neutrino, one of nature’s most ghostly and abundant elementary particles.Neutrinos, electrically neutral particles that sense only gravity and the weak nuclear force, interact so feebly with matter that 100 trillion zip unimpeded through your body every second. They come in three known types: electron, muon and tau. The Daya Bay results suggest the possibility that a fourth, even more ghostly type of neutrino exists —...

In the fall of 2019, Betelgeuse began dimming significantly, losing about two-thirds of its brightness by February. This dramatic dip spurred speculation that the star's demise may have been imminent — perhaps just weeks away. But the dramatic sky show didn't happen: Betelgeuse powered through the dimming episode and returned to its normal brightness by May of this year. The recovery sparked a new round of speculation, this time about the dimming's cause. Some scientists attributed the doldrums to a light-blocking dust cloud, for example, whereas others said big starspots on Betelgeuse's surface were likely to blame. A new study...

Most FRBs originate hundreds of millions of light-years away. This one came from inside the Milky Way. Thirty thousand years ago, a dead star on the other side of the Milky Way belched out a powerful mixture of radio and X-ray energy. On April 28, 2020, that belch swept over Earth, triggering alarms at observatories around the world. The signal was there and gone in half a second, but that's all scientists needed to confirm they had detected something remarkable: the first ever "fast radio burst" (FRB) to emanate from a known star within the Milky Way, according to a...

Metrology is the science of estimations and measurements. We are used to dealing with probabilities that range from 0% (never happens) to 100% (always happens). To explain results from the quantum world however, the concept of probability needs to be expanded to include a so-called quasi-probability, which can be negative. This quasi-probability allows quantum concepts such as Einstein's 'spooky action at a distance' and wave-particle duality to be explained in an intuitive mathematical language. An experiment whose explanation requires negative probabilities is said to possess 'quantum negativity.' In state-of-the-art metrology however, the probes are quantum particles, which can be controlled...

Last year, scientists detected the most energetic gamma ray burst we've ever seen. A distant galaxy spat out a colossal flare in the range of a trillion electron volts (TeV), providing invaluable new insight into the physics of these incredibly energetic events. That was pretty amazing on its own - but now astrophysicists have used the burst to perform a new, precise test of the theory of general relativity. And - quelle surprise! - this test found that the speed of light is constant in a vacuum. Relativity, once again, has passed with flying colours. The test hinges on a...

Artist's conception. Image: Caltech/R. Hurt (IPAC) Astronomers from Caltech have reported that they’ve observed a collision between two black holes. Normally such an event is invisible, but this time a more massive black hole sitting nearby helped illuminate the other two as they collided. If confirmed, the findings, published in Physical Review Letters, would be the first optical observations ever made of a black hole merger. What happened: First detected in May 2019 and dubbed S190521g, the merger happened about 4 billion light-years away, within the vicinity of a supermassive black hole called J1249+3449. This object is 100 million times...

A small team of researchers at Purdue University has found the strongest evidence yet of the existence of abelian anyons. They have written a paper describing experiments they conducted designed to reveal the existence of the quasiparticles and have uploaded it to the arXiv preprint server while they await peer review. Anyons are neither bosons nor fermions—in fact, they are not elementary particles at all. Instead, they are classified as quasiparticles that exist in two dimensions. They can be observed, theoretically speaking, when they appear as disturbances in two-dimensional sheets of materials. Theoretical physicists have suggested their existence since the...

All tetraquarks and pentaquarks that have been discovered so far contain two charm quarks, which are relatively heavy, and two or three light quarks – up, down or strange. This particular configuration is indeed the easiest to discover in experiments. But the latest tetraquark discovered by LHCb, which has been dubbed X(6900), is composed of four charm quarks. Produced in high-energy proton collisions at the Large Hadron Collider, the new tetraquark was observed via its decay into pairs of well-known particles called J/psi mesons, each made of a charm quark and a charm antiquark. This makes it particularly interesting as...

There's something unusual lurking out in the depths of space: Astronomers have discovered four faint objects that at radio wavelengths are highly circular and brighter along their edges. And they're unlike any class of astronomical object ever seen before. The objects, which look like distant ring-shaped islands, have been dubbed odd radio circles, or ORCs, for their shape and overall peculiarity. Astronomers don't yet know exactly how far away these ORCs are, but they could be linked to distant galaxies. All objects were found away from the Milky Way's galactic plane and are around 1 arcminute across (for comparison, the...

Could the Big Bang have created a hidden 'twin' Universe?

Big bounces may make the Universe able to support stars and life. A bouncing universe that expands and then shrinks every trillion years or so could explain one of the most puzzling problems in cosmology: how we can exist at all. If this explanation, proposed in Science1 by Paul Steinhardt at Princeton University, New Jersey, and Neil Turok at the University of Cambridge, UK, seems slightly preposterous, that can't really be held against it. Astronomical observations over the past decade have shown that "we live in a preposterous universe", says cosmologist Sean Carroll of the University of Chicago. "It's our...

Images from the Hubble Space Telescope have revealed a so-called "ring of dark matter" circling a galaxy cluster. Does dark matter exist? Or is electricity a better explanation for the structure of the universe? {Galaxy Cluster CL0024+17 with an overlay showing a supposed dark matter ring. Credit: NASA, ESA, M. J. Jee and H. Ford et al. (Johns Hopkins University)} In a recent announcement, NASA and the European Space Agency (ESA) reported the discovery of something in deep space that seems to confirm previously inferred observations of "dark matter." Although "dark matter" cannot be seen or detected by instruments, its...

Astronomers have been grappling with the mystery of dark matter for a long time, and I mean a looong time. The history of dark-matter investigations goes back at least to 1906, when physicist Henri Poincaré’s 1906 speculated about the amount of “matière obscure” in the Milky Way. Or really, it goes to back to 1846 and the first successful detection of dark matter: the discovery of the planet Neptune, whose existence had been inferred by its gravitational pull well before it was actually observed. Since then, scientists have identified many different dark components in space: collapsed stars, interstellar dust, hot...

(CNN)The fastest-growing black hole in the universe is 34 billion times the mass of our sun and feasts on a meal the equivalent of our sun each day, according to a new study. This massive, hungry black hole was first identified and studied by researchers in May 2018. Previously, they believed it consumed the mass equivalent to our sun every two days. Now, they have a better understanding of this monster black hole and its gluttonous behavior. The study published Wednesday in the journal Monthly Notices of the Royal Astronomical Society. The black hole is known as J2157 and exists...

Leonard Susskind interview - If the deep laws of the universe had been ever so slightly different, human beings wouldn't, and couldn't, exist. All explanations of this exquisite fine-tuning, obvious and not-so-obvious, have problems or complexities.

On Aug. 14, 2019, a gravitational wave -- a massive ripple through the fabric of space-time -- washed over the Earth. The signal was one of the strongest ever seen by the gravitational wave scientists at the Laser Interferometer Gravitational-wave Observatory and Italy's Virgo observatory. After an alert was sent out moments after detection, teams of astronomers across the world turned their telescopes to the point in space that the wave emanated from. But their searches came up empty. No light, no X-rays, no infrared, no gamma rays. On Tuesday, researchers from the LIGO and Virgo collaborations detail their full...

Europe’s preeminent particle-physics organization will need global help to fund the project, which is expected to cost at least €21 billion and would be a follow-up to the lab’s famed Large Hadron Collider. The new machine would collide electrons with their antimatter partners, positrons, by the middle of the century. The design—to be built in an underground tunnel near CERN’s location in Geneva, Switzerland—will enable physicists to study the properties of the Higgs boson and, later, to host an even more powerful machine that will collide protons well into the second half of the century. The approval is not yet...