Physics

From Phys.org: Physicists have implemented the first experimental demonstration of everlasting quantum coherence—the phenomenon that occurs when a quantum system exists in a superposition of two or more states at once. Typically, quantum coherence lasts for only a fraction of a second before decoherence destroys the effect due to interactions between the quantum system and its surrounding environment. The collaboration of physicists, led by Gerardo Adesso at The University of Nottingham and with members from the UK, Brazil, Italy, and Germany, have published a paper on the demonstration of the extreme resilience of quantum coherence in a recent issue of Physical Review Letters. “Quantum properties can be exploited for disruptive technologies but are typically very fragile,” Adesso told Phys.org. “Here Read More ›

Over in this thread, a number of us have been having a discussion with daveS regarding the alleged possibility of an actually infinite past. DaveS seems to think that an infinite past is a perfectly viable model that does not entail any logical contradictions.  Various arguments for the necessary finitude of the past were offered in that thread by myself and others, however, in comment #187 I offered the following argument for the finitude of the past that did not rely on the impossibility of an actual infinite existing in the world: 1) The past consists of moments that were once the present 2) If the past is infinite, then for any given moment there were infinitely many moments that Read More ›

MathematicianRoger Penrose recently published Fashion, Faith, and Fantasy in the New Physics of the Universe, reviewed by Richard Dawid in Nature. Dawid is peeved: There are similar issues with Penrose’s claim that fashion is the main reason for string theory’s influential position. His analysis of its problems is not up to the task of debunking proponents’ physics-based reasons for confidence. Penrose’s main complaint about string theory is that it lacks a clear specification of its number of degrees of freedom. He tries to show this in several contexts. However, he tends to omit information that could make the situation less confusing than he takes it to be. For example, he expresses unease about ‘gauge–gravity duality’, the claim that string theory Read More ›

From Hugh Ross at Salvo: With access to gravitational waves emanating from both medium-sized and supermassive black hole binaries, astronomers will be able to explore new properties of gravity and general relativity. They will be able to determine in much more detail the formation histories of both stars and galaxies in the universe. These advances will lead to a more precise understanding of the cosmic creation event and the subsequent development of the universe. Inevitably, worldviews will come into play, but scientific testing can and should overcome preconceived ideas. How did our universe come to exist? Was it by chance? For a fair-minded person, the understanding to be gained by these advances promises to remove any remaining doubts about the Read More ›

From Charles Q. Choi at Inside Science News: Now researchers examining 153 galaxies find that by looking solely at where stars and gases in those galaxies are located, they could precisely predict the anomalous ways in which they moved. This may hint that dark matter is more strongly coupled to normal matter than currently thought. It could also indicate that dark matter does not exist and that another explanation is needed for the discrepancies that dark matter models were invoked to solve, said study lead author Stacy McGaugh, an astrophysicist and chair of astronomy at Case Western Reserve University in Cleveland. Previous analyses of the orbital velocities of the stars in galaxies often depended on visible wavelengths of light. However, Read More ›

From ScienceDaily, re UC Berkeley’s Richard Muller’s new book NOW: The Physics of Time (W. W. Norton) Ever since the Big Bang explosively set off the expansion of the universe 13.8 billion years ago, the cosmos has been growing, something physicists can measure as the Hubble expansion. They don’t think of it as stars flying away from one another, however, but as stars embedded in space and space continually expanding. Muller takes his lead from Albert Einstein, who built his theory of general relativity — the theory that explains everything from black holes to cosmic evolution — on the idea of a four-dimensional spacetime. Space is not the only thing expanding, Muller says; spacetime is expanding. And we are surfing Read More ›

From Avery Thompson at Popular Mechanics: The Second Law of Thermodynamics is the reason you can’t go back to the past. The universe, like an unmixed cup of coffee, started in an extremely ordered state. Over time, the universe mixed together and became less ordered, like what happens when you stir the coffee. Going back in time is unmixing; it can’t be done. The universe can’t be ‘unmixed’. What this means, ultimately, is that time only exists because the Big Bang created a universe that started out ordered. More. There is also a law of conservation of information that would be worth looking out. Biologist Peter Medawar used it in the 1980s to refer to mathematical and computational systems that Read More ›

From Jeff Hecht at Nature: Most of the Universe is missing. The motion of the stars and galaxies allows astronomers to weigh it, and when they do, they see a major discrepancy in cosmological accounting. For every gram of ordinary matter that emits and absorbs light, the Universe contains around five grams of matter that responds to gravity, but is invisible to light. Physicists call this stuff dark matter, and as the search to identify it is now in its fourth decade, things are starting to get a little desperate.More. Actually, they are better off than the Darwinists. At last they realize they have a problem. See also: Dark matter: Skeptics wanted Follow UD News at Twitter!

From Wayne Rossiter,, author of Shadow of Oz: Theistic Evolution and the Absent God, on the recent claim that time is all in our heads: 1) Don’t a series of events have to pass in order to arrive at a state of the universe in which observers can exist? On atheistic naturalism, doesn’t intelligent life emerge from non-life at one or more places in the cosmos, after some cosmic evolution? If the passage of time is directly related to the experience of the observer, how could time pass leading up to the first observer (or was there no time back there)? 2) What qualifies as an observer? Sure, us (humans). But what/who else? 3) Okay, a third one: If an observer is Read More ›

From Huw Price and Ken Wharton at Aeon: Over the past forty years, a lot of ingenuity has gone into designing experiments to test the quantum predictions on which Bell’s result depends. Quantum mechanics has passed them all with flying colours. Just last year, three new experiments claimed to close almost all the remaining loopholes. ‘The most rigorous test of quantum theory ever carried out has confirmed that the “spooky action-at-a-distance” that [Einstein] famously hated… is an inherent part of the quantum world,’ as Nature put it. Our authors propose another solution: Retrcausality, or the present an future can shape the past: Some readers may raise a more global objection to retrocausality. Ordinarily, we think that the past is fixed Read More ›

Adam Frank confronts the question at NPR: One difference, he says, is data: There are literally thousands of studies now of those rotating-too-fast galaxies out there — and they all get the same, quite noticeable result. In other words, data for the existence of dark matter is prevalent. It’s not like you see the effect once in a while but then it disappears. The magnitude of the result — meaning its strength — also stays pretty consistent from one study to the next. The same holds true for studies of dark energy. No such luck with ghosts. Sure, but a true believer in ghosts would be sure to point out that ghosts are considered intelligent, not inanimate. So seeing them Read More ›

So reports Andrea Taroni at New Scientist: Chances are, too, you’re nowhere near the vision of particles painted by our best picture of how they work, quantum theory. This says that despite making up stuff that definitely has a size – ourselves, the paper or screen you’re reading this on – particles occupy a point in space precisely zero metres across. While you’re chewing that one over, you might consider how quantum theory also allows these size-zero particles to occupy multiple places at once, or be “entangled” so the state of one becomes inextricably bound up with the state of another. But even that doesn’t prepare you for the latest assault on any common-sense conception of a particle that physicists Read More ›

From Dan Falk at Quanta, Many physicists have made peace with the idea of a block universe, arguing that the task of the physicist is to describe how the universe appears from the point of view of individual observers. To understand the distinction between past, present and future, you have to “plunge into this block universe and ask: ‘How is an observer perceiving time?’” said Andreas Albrecht, a physicist at the University of California, Davis, and one of the founders of the theory ofcosmic inflation. Others vehemently disagree, arguing that the task of physics is to explain not just how time appears to pass, but why. For them, the universe is not static. The passage of time is physical. “I’m Read More ›

From Emily Conover at ScienceNews: A beautiful but unproved theory of particle physics is withering in the harsh light of data. For decades, many particle physicists have devoted themselves to the beloved theory, known as supersymmetry. But it’s beginning to seem that the zoo of new particles that the theory predicts —the heavier cousins of known particles — may live only in physicists’ imaginations. Or if such particles, known as superpartners, do exist, they’re not what physicists expected. New data from the world’s most powerful particle accelerator — the Large Hadron Collider, now operating at higher energies than ever before — show no traces of superpartners. More. Will we accept that or move toward throwing out falsifiability? See also: Supersymmetry Read More ›

From Ross Pomeroy at RealClearScience: Recently, Nir Lahav, a physicist at Bar-Ilan University in Israel, went searching for this nucleus of conscious activity. He and his interdisciplinary team, which also included neuroscientists and mathematicians, used detailed scans of six brains to assemble an information map of the human cortex, the brain’s outer layer of neural tissue. With the map, they observed and recorded how certain parts of the cortex were connected to other parts. They charted regions of high connectivity and regions of low connectivity. The map approximated how information “flows” within the cortex, and showed where that flow is concentrated. The region with the highest traffic may very well be the seat of consciousness.More. But what about those people Read More ›