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pierredv : physics   109

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Schrödinger’s kittens: New thought experiment breaks quantum theory | New Scientist, issue 3222, Mar 2019
"A twist on the famous Schrödinger’s cat thought experiment could undermine quantum physics – or provide a path to a deeper understanding of how the world works"
physics  quantum-mechanics  measurement  paradoxes  NewScientist 
5 days ago by pierredv
What do you want on your tombstone?
"I've come across a few mathematicians or scientists who have been so proud of their scholarly achievements that they've asked for them to be put on their headstone when they die (or have had their achievements placed on their headstones by someone else)."
history  obituary  physics  memory 
4 weeks ago by pierredv
The Dirac Equation
Good explanation of derivation and consequence
Dirac  physics  quantum-mechanics 
5 weeks ago by pierredv
Boltzmann's Grave
"Physicist’s epitaph provides final confirmation to a career of turmoil."
Vienna  physics  history  travel  Austria  people  stories 
5 weeks ago by pierredv
Life’s secret ingredient: A radical theory of what makes things alive | New Scientist, issue 3215, Feb 2019
I couldn't figure out what he was on about.
Lots of "arguments by ethos" i.e. citing big name people to support his arguments
See also

maxwell demons

"Physicists and chemists use the language of material objects, and concepts such as energy, entropy, molecular shapes and binding forces. These enable them to explain, for example, how cells are powered or how proteins fold: how the hardware of life works, so to speak. Biologists, on the other hand, frame their descriptions in the language of information and computation, using concepts such as coded instructions, signalling and control: the language not of hardware, but of software."
physics  biology  NewScientist  entropy  Maxwell-demons  thermodynamics 
10 weeks ago by pierredv
From Stories to Scientific Models and Back: Narrative framing in modern macroscopic physics: International Journal of Science Education: Vol 37, No 5-6

Narrative in science learning has become an important field of inquiry. Most applications of narrative are extrinsic to science—such as when they are used for creating affect and context. Where they are intrinsic, they are often limited to special cases and uses. To extend the reach of narrative in science, a hypothesis of narrative framing of natural and technical scenes is formulated. The term narrative framing is used in a double sense, to represent (1) the enlisting of narrative intelligence in the perception of phenomena and (2) the telling of stories that contain conceptual elements used in the creation of scientific models of these phenomena. The concrete case for narrative framing is made by conceptual analyses of simple stories of natural phenomena and of products related to modern continuum thermodynamics that reveal particular figurative structures. Importantly, there is evidence for a medium-scale perceptual gestalt called force of nature that is structured metaphorically and narratively. The resulting figurative conceptual structure gives rise to the notion of natural agents acting and suffering in storyworlds. In order to show that formal scientific models are deeply related to these storyworlds, a link between using (i.e. simulating) models and storytelling is employed. This link has recently been postulated in studies of narrative in computational science and economics.
science  physics  narrative  stories  education 
12 weeks ago by pierredv
A quantum experiment suggests there’s no such thing as objective reality - MIT Technology Review apr 2019
Via John Helm

"Physicists have long suspected that quantum mechanics allows two observers to experience different, conflicting realities. Now they’ve performed the first experiment that proves it."

"last year Caslav Brukner, at the University of Vienna in Austria, came up with a way to re-create the Wigner’s Friend experiment in the lab by means of techniques involving the entanglement of many particles at the same time. The breakthrough that Proietti and co have made is to carry this out."

"The idea that observers can ultimately reconcile their measurements of some kind of fundamental reality is based on several assumptions."

<list follows>

"Proietti and co’s result suggests that objective reality does not exist. In other words, the experiment suggests that one or more of the assumptions—the idea that there is a reality we can agree on, the idea that we have freedom of choice, or the idea of locality—must be wrong."
MIT-Technology-Review  physics  quantum-mechanics  reality 
april 2019 by pierredv
Confirmed: New phase of matter is solid and liquid at same time - National Geographic Apr 2019
Via Linda Chang

"a team has used a type of artificial intelligence to confirm the existence of a bizarre new state of matter, one in which potassium atoms exhibit properties of both a solid and a liquid at the same time. If you were somehow able to pull out a chunk of such material, it would probably look like a solid block leaking molten potassium that eventually all dissolved away."
NationalGeographic  science  solid-state  physics 
april 2019 by pierredv
Exclusive: Grave doubts over LIGO's discovery of gravitational waves | New Scientist Nov 2018
“We believe that LIGO has failed to make a convincing case for the detection of any gravitational wave event,” says Andrew Jackson, the group’s spokesperson. According to them, the breakthrough was nothing of the sort: it was all an illusion.
LIGO  gravity  cosmology  experiment  NewScientist  physics 
april 2019 by pierredv
(66) Physics Professors Be Like - YouTube
"I've made joke videos about physics students, now it's time for the professors."
physics  education  humor  video  YouTube 
april 2019 by pierredv
Famous Experiment Dooms Pilot-Wave Alternative to Quantum Weirdness | Quanta Magazine
"There and in bouncing-droplet labs that soon sprang up at the Massachusetts Institute of Technology and elsewhere, droplets were seen to tunnel through barriers and perform other acts previously thought to be uniquely quantum. In reproducing quantum phenomena without any of the mystery, the bouncing-droplet experiments rekindled in some physicists de Broglie’s old dream of a reality at the quantum scale that consists of pilot waves and particles instead of probability waves and conundrums.

But a series of bouncing-droplet findings since 2015 has crushed this dream."
quantum-mechanics  physics 
october 2018 by pierredv
Quantum Amplitudes, Classical Ignorance & Quantum Information Processing | Saturday Mornings of Theoretical Physics, June 2018
Saturday, June 30, 2018 - 10:30
Martin Wood Lecture Theatre, Clarendon Laboratory

A major theme in current theoretical physics is understanding the implications of quantum mechanics for the dynamics of composite systems. When sub-systems interact, they naturally become correlated. In the 1980s it was realised that by exploiting the correlations between quantum sub-systems it should be possible to (i) break current cryptographic systems by rapidly decomposing large numbers into their prime factors, and (ii) exchange confidential information in the secure knowledge that messages have not been intercepted. As we have become ever more dependent on the internet these explosive implications of quantum mechanics for cryptography have driven efforts to build quantum communication channels and quantum computers.

On June 30, to mark the completion of the Beecroft Building, the members of the Rudolf Peierls Centre for Theoretical Physics, who occupy the building above ground, and the members of the Quantum Information Technology hub (NQIT), who are installing kit in many of its subterranean laboratories, will join forces to explain the basic principles underlying the quantum dynamics of composite systems and to describe the challenge of implementing quantum computation and cryptography practically.

In the afternoon there will be three talks from NQIT, which is led by Oxford University. A general introduction to the programme will be followed by two talks about using ion traps and photonics to build a quantum computer. There will also have a chance to see the new labs via exclusive video and an opportunity to questions NQIT researchers.
Oxford  physics  quantum-mechanics  lectures 
july 2018 by pierredv
This physicist's ideas of time will blow your mind — Quartz May 2018
via Adriana Shum
Feature on Carlo Rovelli's ideas
"Rovelli’s new book, The Order of Time, published in April, is about our experience of time’s passage as humans, and the fact of its absence at minuscule and vast scales. He makes a compelling argument that chronology and continuity are just a story we tell ourselves in order to make sense of our existence."
time  physics  Carlo-Rovelli  Quartz 
may 2018 by pierredv
Richard Feynman at 100 - Nature May 2018
Paul Halpern celebrates the oeuvre of the brilliant, unconventional scientist.
physics  quantum-mechanics  Richard-Feynman  people  biography  NatureJournal 
may 2018 by pierredv
Stephen Hawking Asked To Have This Equation On His Tombstone. Here's What It Means | IFLScience - 2018
His most famous formula, describing the entropy of a black hole, might even adorn his tombstone. He declared his wishes for this in 2002, during a workshop on the future of theoretical physics and cosmology held to mark his 60th birthday.
physics  epitaphs  death 
may 2018 by pierredv
Fourier’s transformational thinking - Nature Mar 2018
Via Dale Hatfield

"The mathematics of Joseph Fourier, born 250 years ago this week, shows the value of intellectual boldness."
physics  history  profile  NatureJournal  maths 
march 2018 by pierredv
‘Wavelet revolution’ pioneer scoops top maths award : Nature News & Comment - Mar 2017
"French mathematician Yves Meyer has won the 2017 Abel Prize for his “pivotal role” in establishing the theory of wavelets — data-analysis tools used in everything from pinpointing gravitational waves to compressing digital films."
physics  NatureJournal  maths 
march 2018 by pierredv
The geometry that could reveal the true nature of space-time | New Scientist issue 3136, 29 Jul 2017
"The discovery of an exquisite geometric structure is forcing a radical rethink of reality, and could clear the way to a quantum theory of gravity"

[Andrew Hodges, one of Penrose’s colleagues at Oxford] "showed that the various terms used in the BCFW method could be interpreted as the volumes of tetrahedrons in twistor space, and that summing them up led to the volume of a polyhedron."

"So why invoke virtual particles at all? ... The first is that dealing with them rather than with fields makes the maths more tractable. The other great advantage is that they help physicists visualise everything as the well-defined interactions between point-like particles, as opposed to the hazy goings-on between particles and fields. This fits nicely with the intuitive principle of locality, which holds that only things in the same spot in space and time can interact. Finally, the technique also helps enforce the principle of unitarity, which says that the probability of all outcomes should add up to 1."

Gluon interactions seemed to complex, but "In 1986, Stephen Parke and Tomasz Taylor from Fermilab near Batavia, Illinois, used Feynman diagrams and supercomputers to calculate the likelihoods of different outcomes for interactions involving a total of six gluons. A few months later, they made an educated guess at a one-line formula to calculate the same thing. It was spot on. More than 200 Feynman diagrams and many pages of algebra had been reduced to one equation, and the researchers had no idea why."

"In 2005, Ruth Britto, Freddy Cachazo, Bo Feng and Edward Witten [BCFW] were able to calculate scattering amplitudes without recourse to a single virtual particle and derived the equation Parke and Taylor had intuited for that six-gluon interaction"

[Nima Arkani-Hamed and his team at IAS] "arrived at a mind-boggling conclusion: the scattering amplitude calculated with the BCFW technique corresponds beautifully to the volume of a new mathematical object. They gave a name to this multi-dimensional concatenation of polyhedrons: the amplituhedron."

"It may transform physics, too ... because the amplituhedron does not embody unitarity and locality, those core principles baked into reality as described by Feynman diagrams. ... If so, locality is not a fundamental feature of space-time but an emergent one."
NewScientist  geometry  physics  gravity  field-theory  quantum-mechanics  twistors  Roger-Penrose  Richard-Feynman  Ed-Witten  maths 
december 2017 by pierredv
Gel-like ice is the lightest form of water ever discovered | New Scientist, Sep 2017
via John Helm

"The frosty cubes we pull from our freezers are just one of 17 possible types of ice, and an 18th type isn’t far from being made real. A team of researchers has now discovered a type of porous, lightweight “aeroice” – the aerogel of ice, if you will – that can tell us more about how water works under extreme conditions."
NewScientist  water  physics  chemistry 
september 2017 by pierredv
Reality check: The hidden connections behind quantum weirdness | New Scientist, April 2017
Love the physical analogy to a QM pilot wave in the bouncing oil droplet experiment

"Bohm proposed there was a hidden reality to quantum theory, meaning its crazy predictions of a world that doesn’t exist until you choose to look at it are just that: crazy."

As an alternative to the Copenhagen interpretation, "De Broglie suggested another: that particles are real and have equally real waves associated with them. In this picture, when a particle goes through one of the double slits, its “pilot” wave goes through both, interferes with itself, and then guides the particle to a location on the screen. . . . Bohm’s ideas made de Broglie revisit and revise his own pilot-wave theory. He developed a two-wave theory in which every particle rides a pilot wave, which in turn interacts with another wave that behaves like a wave function."

Also explains entanglement: "In the alternative picture, though, if particles are entangled, a common pilot wave guides them, and any change in the position or momentum of one particle instantly changes the pilot wave, thus influencing all the other particles."

" In 2005, Yves Couder and Emmanuel Fort at Denis Diderot University in Paris stumbled upon a physical analogue of pilot waves. . . . The interesting thing was what happened when this wave-particle system encountered a barrier, a fraction of a millimetre below the surface, with two gaps in it: a double slit. The walking droplet went over one or the other slit, while its pilot wave went over both, and the wave pattern that emerged on the other side guided the droplet on. "

Improved experiment: Pucci, ... and Bush, "Non-specular reflection of walking droplets" (Journal of Fluid Mechanics, DOI: 10.1017/jfm.2016.537,

1. "Bohmian mechanics is formulated to replicate the predictions of standard quantum mechanics: experimentally, it’s almost impossible to tell them apart"
2. not relativistic
NewScientist  quantum-mechanics  physics 
august 2017 by pierredv
No-fly zone: Exploring the uncharted layers of our atmosphere | New Scientist issue 3087, 20 Aug 2016
"This unknown zone increasingly matters to us. We are sending up ever more satellites, which are vulnerable to flare-ups in the ignorosphere. Electrical disturbances in this region can scramble GPS signals and other communications. And its influence may even stretch down to ground level and alter our weather. So we need to understand this rarefied air – and to do so, we must go and explore it.

"The ignorosphere encompasses those in-between altitudes that we find extremely hard to navigate. Above about 50 kilometres – where the stratosphere ends – the air becomes too thin to support research balloons. And below 300 km, it is too thick for satellites to survive the drag forces for more than a few months.

"Within this zone are two starkly different layers. Lower down is the icy mesosphere, ... Above the mesosphere is the thermosphere, heated to thousands of degrees by ultraviolet light."

"The QB50 project will see a fleet of CubeSats, each 20 by 10 by 10 centimetres, entering the ignorosphere. "

From the sidebar, "Save our Satellites"

"The solar storms that create the aurora inject heat and ionised plasma into the upper atmosphere, causing it to puff up and thus increase the drag on satellites in low Earth orbit. Sometimes this is so sudden that space agencies can lose track of their expensive property. “After intense solar activity, NASA has lost hundreds of satellites,” says Jan Thoemel at the von Karman Institute in Sint-Genesius-Rode, Belgium. Even small solar storms can throw their trajectories off a little. That’s no mere inconvenience: the ISS and other satellites must already navigate with care to avoid space junk, and collisions will become more of a risk as low Earth orbit gets more crowded."

"During the major solar storm of October 2003, GPS positions were thrown off by hundreds of metres."
NewScientist  atmosphere  CubeSats  physics  solar-storms  NASA 
april 2017 by pierredv
Fleet of CubeSats launches to study the neglected 'ignorosphere' | New Scientist April 2017
The 28 boxy satellites are part of QB50, an international mission to explore Earth’s lower thermosphere. Stretching from about 90 to 300 kilometres above ground level, this turbulent region is stirred from above by solar storms and flares, and from below by terrestrial weather. In its unpredictable moods it can scatter satellites and scramble GPS, so scientists would love to learn more about the gas and plasma up there.

But this upper air is far too thin to support research planes or balloons, while still thick enough to drag down spacecraft in a matter of months. Ground-based observations are no substitute for measurements in situ. Although a few satellites have taken measurements on their way back down to Earth, “these are sparse data, with no continuity”, says QB50 project manager Davide Masutti at the von Karman Institute in Sint-Genesius-Rode, Belgium. This lack of information has given this region its nickname: the ignorosphere.
NewScientist  atmosphere  CubeSats  physics 
april 2017 by pierredv
A Recreation of a Supernova Using Ink and Water by Thomas Vanz
"A fantastic recreation of a supernova using only an aquarium filled with ink and water by independent film maker and motion designer Thomas Vanz based in Magny, France. "
Faith-is-Torment  physics  astronomy  video  vimeo  art 
november 2016 by pierredv
The Case Against Reality - The Atlantic
"Donald D. Hoffman, a professor of cognitive science at the University of California, Irvine. Hoffman has spent the past three decades studying perception, artificial intelligence, evolutionary game theory and the brain, and his conclusion is a dramatic one: The world presented to us by our perceptions is nothing like reality. What’s more, he says, we have evolution itself to thank for this magnificent illusion, as it maximizes evolutionary fitness by driving truth to extinction."
"So while neuroscientists struggle to understand how there can be such a thing as a first-person reality, quantum physicists have to grapple with the mystery of how there can be anything but a first-person reality. In short, all roads lead back to the observer. And that’s where you can find Hoffman—straddling the boundaries, attempting a mathematical model of the observer, trying to get at the reality behind the illusion."
"Gefter: So everything we see is one big illusion?
Hoffman: We’ve been shaped to have perceptions that keep us alive, so we have to take them seriously. If I see something that I think of as a snake, I don’t pick it up. If I see a train, I don’t step in front of it. I’ve evolved these symbols to keep me alive, so I have to take them seriously. But it’s a logical flaw to think that if we have to take it seriously, we also have to take it literally."
reality  perception  physics  philosophy  TheAtlantic  cognition 
september 2016 by pierredv
The snarXiv « David Simmons-Duffin
The snarXiv is a random high-energy theory paper generator incorporating all the latest trends, entropic reasoning, and exciting moduli spaces. The arXiv is similar, but occasionally less random
physics  humor 
september 2016 by pierredv
Albert Einstein and Henri Bergson’s Great Showdown About the Nature of Time
"What Einstein said next that evening was even more controversial: “There remains only a psychological time that differs from the physicist’s.” At that very moment, Einstein laid down the gauntlet by considering as valid only two ways of understanding time: physical and psychological. "
"Einstein’s and Bergson’s contributions appeared to their contemporaries forcefully at odds, representing two competing strands of modern times. Bergson was associated with metaphysics, antirationalism, and vitalism, the idea that life permeates everything. Einstein with their opposites: with physics, rationality, and the idea that the universe (and our knowledge of it) could stand just as well without us. "
"The theory of relativity broke with classical physics in three main respects: first, it redefined concepts of time and space by claiming that they were no longer universal; second, it showed that time and space were completely related; and third, the theory did away with the concept of the ether, a substance that allegedly filled empty space and that scientists hoped would provide a stable background to both the universe and their theories of classical mechanics."
"Bergson found Einstein’s definition of time in terms of clocks completely aberrant. The philosopher did not understand why one would opt to describe the timing of a significant event, such as the arrival of a train, in terms of how that event matched against a watch. He did not understand why Einstein tried to establish this particular procedure as a privileged way to determine simultaneity. Bergson searched for a more basic definition of simultaneity, one that would not stop at the watch but that would explain why clocks were used in the first place."
Einstein  Bergson  philosophy  Nautilus  physics  relativity 
june 2016 by pierredv
A New Thermodynamics Theory Of The Origin Of Life | Quanta Magazine
Interview with Jeremy England
"From the standpoint of physics, there is one essential difference between living things and inanimate clumps of carbon atoms: The former tend to be much better at capturing energy from their environment and dissipating that energy as heat. Jeremy England, a 31-year-old assistant professor at the Massachusetts Institute of Technology, has derived a mathematical formula that he believes explains this capacity. The formula, based on established physics, indicates that when a group of atoms is driven by an external source of energy (like the sun or chemical fuel) and surrounded by a heat bath (like the ocean or atmosphere), it will often gradually restructure itself in order to dissipate increasingly more energy. This could mean that under certain conditions, matter inexorably acquires the key physical attribute associated with life."
"Life does not violate the second law of thermodynamics, but until recently, physicists were unable to use thermodynamics to explain why it should arise in the first place. ... In the 1960s, the Belgian physicist Ilya Prigogine made progress on predicting the behavior of open systems weakly driven by external energy sources (for which he won the 1977 Nobel Prize in chemistry). But the behavior of systems that are far from equilibrium, which are connected to the outside environment and strongly driven by external sources of energy, could not be predicted.... Jarzynski and Crooks showed that the entropy produced by a thermodynamic process, such as the cooling of a cup of coffee, corresponds to a simple ratio: the probability that the atoms will undergo that process divided by their probability of undergoing the reverse process (that is, spontaneously interacting in such a way that the coffee warms up). As entropy production increases, so does this ratio: A system’s behavior becomes more and more “irreversible.”"
"Using Jarzynski and Crooks’ formulation, [England] derived a generalization of the second law of thermodynamics that holds for systems of particles with certain characteristics: The systems are strongly driven by an external energy source such as an electromagnetic wave, and they can dump heat into a surrounding bath. This class of systems includes all living things."
“It is very tempting to speculate about what phenomena in nature we can now fit under this big tent of dissipation-driven adaptive organization,” England said. “Many examples could just be right under our nose, but because we haven’t been looking for them we haven’t noticed them.”
<examples of self-replication in non-living systems: vortices in turbulent fluids; specially coated microspheres
physics  biology  life  evolution  information-theory  QuantaMagazine  interviews 
may 2016 by pierredv
Quantum Bayesianism Explained By Its Founder | Quanta Magazine
Interview with Christopher Fuchs
"Those interpretations [Copenhagen, many worlds, Bohmian] all have something in common: They treat the wave function as a description of an objective reality shared by multiple observers. QBism, on the other hand, treats the wave function as a description of a single observer’s subjective knowledge. It resolves all of the quantum paradoxes, but at the not insignificant cost of anything we might call “reality.” Then again, maybe that’s what quantum mechanics has been trying to tell us all along — that a single objective reality is an illusion."
Q. How does QBism get you around those limits?
A. "One way to look at it is that the laws of physics aren’t about the stuff “out there.” Rather, they are our best expressions, our most inclusive statements, of what our own limitations are. When we say the speed of light is the ultimate speed limit, we’re saying that we can’t go beyond the speed of light."
"I’ve become fascinated by these beautiful mathematical structures called SICs, symmetric informationally complete measurements — horrible name, almost as bad as bettabilitarianism. They can be used to rewrite the Born rule [the mathematical procedure that generates probabilities in quantum mechanics] in a different language, in which it appears that the Born rule is somehow deeply about analyzing the real in terms of hypotheticals."
QuantaMagazine  QBism  Bayesian  physics  quantum-mechanics  philosophy  interviews 
may 2016 by pierredv
The Relation between Mathematics and Physics by Paul Adrien Maurice Dirac
Lecture delivered on presentation of the JAMES SCOTT prize, February 6, 1939
Published in: Proceedings of the Royal Society (Edinburgh) Vol. 59, 1938-39, Part II pp. 122-129
physics  beauty  Paul-Dirac  maths 
march 2016 by pierredv
Quantum purity: How the big picture banishes weirdness - New Scientist 11 April 2015
Based on work started by Lucien Hardy. “When I look at quantum theory, I see something that’s akin to the ad hoc nature of Kepler’s laws of planetary motion and of Lorentz transformations,” says Hardy. “What we need is some deeper set of principles.” Could it be that all the messy uncertainty of the quantum world simply stems from lack of information: making a measurement of a mixed state without having access to the larger pure state of which it is part? “The idea is not to get rid of the weirdness, but to explain it as a logical consequence of basic principles,” Chiribella says. "Fivefold way" per D’Ariano, Chiribella, Perinotti: five fundamental principles that must apply to any physical system to make a sensible measurement of it 1 Causality 2 Distinguishability 3 Composition 4 Compression 5 Tomography
NewScientist  explanation  quantum-mechanics  physics  *  information-theory 
august 2015 by pierredv
Kitchen-table physics lets you do big science at home - physics-math - 26 February 2015 - Control - New Scientist
Great stuff, e.g. Jam jar detector of time reversal symmetry - mirror magnetometer: Gravitational wave detector with laser pointer - Michelson interferometer:
science  experiment  NewScientist  fun  DIY  physics  * 
july 2015 by pierredv
25Sep14: Multiverse me: Should I care about my other selves? New Scientist #2988
Very well written discussion of moral-philosophical implications of multiple universes, quoting Tegmark and Deutsch
NewScientist  cosmology  quantum-mechanics  philosophy  physics  religion  morality  parallel.universes  multiverse  probability  risk  *  ethics 
november 2014 by pierredv
The asymmetric Universe | Royal Society - Frank Close
"Modern scientific theory describes a perfectly symmetrical Universe. A Universe in which matter is destroyed within an instant of its appearance and where nothing we now know could ever have happened. Human life itself seems to be lopsided, as the spherical embryo is transformed into a highly structured being with its internal organs mirrored asymmetrically. This talk explores the profound role of asymmetry in nature, and the role of its agent - the Higgs Boson - in creating a Universe fit for life. The Royal Society Michael Faraday Prize is awarded annually to the scientist or engineer whose expertise in communicating scientific ideas in lay terms is exemplary. Professor Frank Close OBE was presented the award for his excellence in science communication."
RoyalSociety  video  physics  cosmology  lectures 
july 2014 by pierredv
The mirror crack'd: Why physics is lopsided - Frank Close, NewScientist May 2014
"Forget symmetry, it's asymmetry that could be the key to life, the universe and almost everything" Survey of symmetry, symm breaking etc. "Even the simplest atom is cockeyed: its protons are complex, yet its electrons are simple. That their charges conspire so beautifully suggests that some deeper symmetry relates electrons to quarks, but as yet we do not know what it is." "The mystery of the missing antimatter – this fundamental asymmetry of the universe – is a great unsolved question." "In such a situation nature chooses stability over symmetry. A symmetric but unstable situation will hide symmetry to attain stability."
physics  stability  symmetry  asymmetry  Frank  Close  wonder  mystery  NewScientist 
july 2014 by pierredv
Carbon, Avogadro's Constant and the Importance of the Number 12
"Materials scientists have decided to define, rather than measure, Avogadro’s constant, triggering a lengthy debate over what number to choose. Now one physicist thinks he has the answer."
arxiv  carbon  chemistry  MITtechnologyreview  physics 
may 2014 by pierredv
Physics: Quantum quest : Nature News & Comment
The lesson, says Fuchs, isn't that Spekkens's model is realistic — it was never meant to be — but that entanglement and all the other strange phenomena of quantum theory are not a completely new form of physics. They could just as easily arise from a theory of knowledge and its limits. To get a better sense of how, Fuchs has rewritten standard quantum theory into a form that closely resembles a branch of classical probability theory known as Bayesian inference “It turns out that many principles lead to a whole class of probabilistic theories, and not specifically quantum theory,” says Schlosshauer.
Bayesian  physics  quantum-mechanics  NatureJournal 
september 2013 by pierredv
Quantum weirdness: The battle for the basis of reality - physics-math - 05 August 2013 - New Scientist
Discussion of explanations of quantum entanglement, with the upshot shot that of the 4, reality, relativity, cause & effect and free will can't all be true at the same time.

"Reality, relativity, causality or free will? Take quantum theory at face value and at least one of them is an illusion – but which?"
free-will  quantum-mechanics  causality  NewScientist  reality  relativity  physics  * 
august 2013 by pierredv
50 years of Revolutions: A classic revisited - opinion - 26 October 2012 - New Scientist
"Normal science, then, is characterised by a paradigm, which legitimises the puzzles and problems on which the community works. All is well until the methods legitimised by that paradigm cannot cope with the anomalies that emerge; a crisis results and persists until a new achievement redirects research and serves as a new paradigm. This is a paradigm shift."
physics  philosophy  opinion  NewScientist  science 
february 2013 by pierredv
Poll Reveals Quantum Physicists' Disagreement About the Nature of Reality | MIT Technology Review
"For example, in answer to the question “Do you believe that physical objects have their properties well defined prior to and independent of measurement?”, 48 per cent replied “no”, while 52 per cent replied “yes, in some cases”. A further 3 per cent said “yes in all cases”   and 9 per cent were undecided (respondents were able to select more than one answer). "
physics  philosophy  quantum-computing  x:mittechnologyreview  polls 
january 2013 by pierredv
The surprise theory of everything -Vlatko Vedral -October 2012 -
"The question is whether we can express the whole of physics simply by enumerating possible and impossible processes in a given situation. This is very different from how physics is usually phrased, in both the classical and quantum regimes, in terms of states of systems and equations that describe how those states change in time. . . ." "Apply this logic more generally, and time ceases to exist as an independent, fundamental entity, but one whose flow is determined purely in terms of allowed and disallowed processes. With it go problems such as that I alluded to earlier, of why the universe started in a state of low entropy. If states and their dynamical evolution over time cease to be the question, then anything that does not break any transformational rules becomes a valid answer."
*  NewScientist  science  thermodynamics  physics  gravity 
november 2012 by pierredv
Physicist Derives Laws of Thermodynamics For Life Itself - Technology Review
"How likely is it that these molecules will arrange themselves into fully-fledged living thing, a bacterium, for example? That's a tough question but Jeremy England at the Massachusetts Institute of Technology in Cambridge has worked out how to calculate an answer, at least in theory."
thermodynamics  physics  life  biology  x:technologyreview 
september 2012 by pierredv
Sometimes science must give way to religion : Nature News & Comment
"Science advocates have been keen to claim that the Higgs discovery is important for everyone. Yet in practical terms, the Higgs is an incomprehensible abstraction, a partial solution to an extraordinarily rarified and perhaps always-incomplete intellectual puzzle. By contrast, the Angkor temples demonstrate how religion can offer an authentic personal encounter with the unknown. At Angkor, the genius of a long-vanished civilization, expressed across the centuries through its monuments, allows visitors to connect with things that lie beyond their knowing in a way that no journalistic or popular scientific account of the Higgs boson can. Put another way, if, in a thousand years, someone visited the ruins of the Large Hadron Collider, where the Higgs experiment was conducted, it is doubtful that they would get from the relics of the detectors and super­conducting magnets a sense of the subatomic world that its scientists say it revealed."
opinion  Angkor  physics  particle-physics  religion  philosophy  NatureJournal 
august 2012 by pierredv
Quantum minds: Why we think like quarks - life - 05 September 2011 - New Scientist
Strapline: "The fuzziness and weird logic of the way particles behave applies surprisingly well to how humans think" Application of Hilbert space theory ("quantum logic") to behavior "We make systematic errors when reasoning with probabilities, for example. Physicist Diederik Aerts of the Free University of Brussels, Belgium, has shown that these errors actually make sense within a wider logic based on quantum mathematics. The same logic also seems to fit naturally with how people link concepts together, often on the basis of loose associations and blurred boundaries. That means search algorithms based on quantum logic could uncover meanings in masses of text more efficiently than classical algorithms." Cites research by Aerts; Tversky & Shafir; Busemeyer & Pothos; Widdows, Cohen; etc.
physics  behavior  maths  NewScientist  quarks  quantum-mechanics 
november 2011 by pierredv
Physicists Recreate 'End Of Time' in Lab - Technology Review
"One of the most exciting areas of science is the emerging field of spacetime analogues. This is the discipline in which physicists play around with systems that have a formal mathematical link with general relativity.
"For example, changes in the way electrons move in graphene as it is cooled are identical to the changes that may have occurred in the universe soon after the big bang. So physicists can use cool graph to test theories about the universe's earliest behaviour. "
Work reported: Igor Smolyaninov at the University of Maryland - created an experiment that models the end of time
physics  x:MITtechnologyreview  x:arXivBlog  time 
august 2011 by pierredv
A Physicist Turns the City Into an Equation -
“This remarkable equation is why people move to the big city,” West says. “Because you can take the same person, and if you just move them to a city that’s twice as big, then all of a sudden they’ll do 15 percent more of everything that we can measure.” But also: "After a city doubles in size, it also experiences a 15 percent per capita increase in violent crimes, traffic and AIDS cases."
via:mindhacks  cities  urbanism  math  physics  NYTimes 
february 2011 by pierredv
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