European Space Agency (Esa) member states have decided to select a mission to Jupiter and its icy moons as their next great venture. Juice, as the spacecraft is currently known, will leave Earth in 2022 on a long journey that should see it returning science from the outer Solar System in the 2030s. The champagne… [Read more…]
May 3, 2012
Incompatibility with special relativity and momentum conservation Masud Mansuripur The Lorentz law of force is the fifth pillar of classical electrodynamics, the other four being Maxwell’s macroscopic equations. The Lorentz law is the universal expression of the force exerted by electromagnetic fields on a volume containing a distribution of electrical charges and currents. If electric… [Read more…]
April 26, 2012
Vasant Natarajan The accepted resolution of the twin paradox in relativity states that the age of the inertial twin `jumps’ when the traveling twin undergoes his turn-around acceleration. This resolution is based on the use of the equivalent gravitational shift in the frame of the accelerating twin. We use the same analysis to propose a… [Read more…]
April 16, 2012
… a lesson for quantum gravity Stefano Finazzi, Stefano Liberati, Lorenzo Sindoni For almost a century, the cosmological constant has been a mysterious object, in relation to both its origin and its very small value. By using a Bose-Einstein condensate analogue model for gravitational dynamics, we address here the cosmological constant issue from an analogue… [Read more…]
April 12, 2012
Panagiota Kanti We review the current results for the emission of Hawking radiation by a higher-dimensional black hole during the Schwarzschild and the spin-down phases. We discuss particularly the role of the angular variation of the emitted radiation on the brane during the latter phase, the radiation spectra for gravitons in the bulk, and the… [Read more…]
March 28, 2012
Read more: physicsworld.com/cws/article/news/49135 Global Positioning System Test of the Local Position Invariance of Planck’s Constant J. Kentosh and M. Mohageg Phys. Rev. Lett. 108, 110801 (2012) Published March 15, 2012 Pinpointing Planck’s Constant with GPS GPS is helping drivers find their way and parents track their kids and pets. But now a pair of researchers—reporting in Physical Review Letters—has used… [Read more…]
March 18, 2012
Einstein’s theory of gravity and quantum physics are expected to merge at the Planck-scale of extremely high energies and on very short distances. At this scale, new phenomena could arise. However, the Planck-scale is so remote from current experimental capabilities that tests of quantum gravity are widely believed to be nearly impossible. Now an international… [Read more…]
March 17, 2012
Dmitri Krioukov, Maksim Kitsak, Robert S. Sinkovits, David Rideout, David Meyer, Marian Boguna Causal sets are an approach to quantum gravity in which the causal structure of spacetime plays a fundamental role. The causal set is a quantum network which underlies the fabric of spacetime. The nodes in this network are tiny quanta of spacetime,… [Read more…]
March 12, 2012
Video: What it would look like to travel through a wormhole IT IS not every day that a piece of science fiction takes a step closer to nuts-and-bolts reality. But that is what seems to be happening to wormholes. Enter one of these tunnels through space-time, and a few short steps later you may emerge near… [Read more…]
January 30, 2012
Physicists have simulated two universes colliding inside a metamaterial One interesting way in which our cosmos may have formed is in a collision between two other universes with extra spatial dimensions called braneworlds. In this scenario, known as the ekpyrotic model of the universe, our cosmos is just a small four-dimensional corner of a much… [Read more…]
January 22, 2012
Claudio Germana ABSTRACT Recent results from the OPERA experiment reported a neutrino beam traveling faster than light. The experiment measured the neutrino time of flight (TOF) over a baseline from the CERN to the Gran Sasso site. The neutrino beam arrives 60 ns earlier than a light ray would do. Because the result has an… [Read more…]
January 18, 2012
Fotini Markopoulou The idea that the Universe is a program in a giant quantum computer is both fascinating and suffers from various problems. Nonetheless, it can provide a unified picture of physics and this can be very useful for the problem of Quantum Gravity where such a unification is necessary. In previous work we proposed… [Read more…]
January 16, 2012
A new telescope array could allow scientists to photograph a black hole for the first time – teaming up 50 radio telescopes around the world into a global telescope that will capture the ‘shadow’ of a black hole for the first time. Scientists will meet on Wednesday 18th to discuss the project, which will also… [Read more…]
January 14, 2012
Mihalis Dafermos It is shown that for small, spherically symmetric perturbations of asymptotically flat two-ended Reissner-Nordstrom data for the Einstein-Maxwell-real scalar field system, the boundary of the dynamic spacetime which evolves is globally represented by a bifurcate null hypersurface across which the metric extends continuously. Under additional assumptions, it is shown that the Hawking mass… [Read more…]
January 4, 2012
Shahar Hod Black-hole spacetimes with a “photonsphere”, a hypersurface on which massless particles can orbit the black hole on circular null geodesics, are studied. We prove that among all possible trajectories (both geodesic and non-geodesic) which circle the central black hole, the null circular geodesic is characterized by the shortest possible orbital period as measured… [Read more…]
January 2, 2012
Astronomer royal and master of Trinity College, Cambridge. Like Hawking, he studied under Dennis Sciama in the 1960s I first met Stephen in 1964. I was in my first week as a Cambridge graduate student. He was two years ahead of me in his studies – but already unsteady on his feet and speaking with… [Read more…]
December 18, 2011
Poincaré and Special Relativity Emily Adlam Henri Poincare’s work on mathematical features of the Lorentz transformations was an important precursor to the development of special relativity. In this paper I compare the approaches taken by Poincare and Einstein, aiming to come to an understanding of the philosophical ideas underlying their methods. In section (1) I… [Read more…]
December 9, 2011
Christoph Adami Information theory is a statistical theory dealing with the relative state of detectors and physical systems. Because of this physicality of information, the classical framework of Shannon needs to be extended to deal with quantum detectors, perhaps moving at relativistic speeds, or even within curved space-time. Considerable progress toward such a theory has… [Read more…]
December 3, 2011
Roberto B. Salgado We present visual calculations in special relativity using spacetime diagrams drawn on graph paper that has been rotated by 45 degrees. The rotated lines represent lightlike directions in Minkowski spacetime, and the boxes in the grid (called “light-clock diamonds”) represent units of measurement modeled on the ticks of an inertial observer’s lightclock.… [Read more…]
November 30, 2011
Harihar Behera, Gautam Mukhopadhyay The invariance of the speed of light in all inertial frames – the second postulate of special theory of relativity (STR) – is shown to be an inevitable consequence of the relativity principle of special theory of relativity taken in conjunction with the homogeneity of space and time in all inertial… [Read more…]
November 15, 2011
Superconducting metal bars could revolutionise the detection of gravitational waves, says physicists Gravitational waves are vibrations in the fabric of spacetime. They are among the most exciting phenomena in the universe because they are generated by exotic processes such as collisions between black holes and even in the moment of creation itself, the Big Bang.… [Read more…]
November 14, 2011
Timothy C. Ralph, Tony G. Downes Relativistic quantum information combines the informational approach to understanding and using quantum mechanics systems – quantum information – with the relativistic view of the universe. In this introductory review we examine key results to emerge from this new field of research in physics and discuss future directions. A particularly… [Read more…]
November 12, 2011
…. “German Scientists for the Preservation of Pure Science,” Relativity, and the Bad Nauheim Meeting Jeroen van Dongen Two important and unpleasant events occurred in Albert Einstein’s life in 1920: That August an antirelativity rally was held in the large auditorium of the Berlin Philharmonic, and a few weeks later Einstein was drawn into a… [Read more…]
November 5, 2011
On ‘Nothing’ Adam R. Brown and Alex Dahlen Abstract Nothing-the absence of spacetime-can be either an endpoint of tunneling, as in the bubble of nothing, or a starting point for tunneling, as in the quantum creation of a universe. We argue that these two tunnelings can be treated within a unified framework, and that, in… [Read more…]
November 2, 2011
Laws we know may be ‘like local by-laws’ say scientists Hints universe is bigger than we think – possibly infinite Other parts of the universe may be hostile to life By ROB WAUGH The laws of physics may not be as set in stone as previously imagined. One of the laws of nature seems to… [Read more…]
November 2, 2011
The daily rumblings from the supermassive black hole at the centre of our galaxy are the last throes of planets and asteroids plunging to their deaths, say astrophysicists At the centre of our galaxy sits a black hole about a million times more massive than our Sun. Called Sagittarius A* or Sgr A*, this supermassive… [Read more…]
October 25, 2011
Rainer Collier The classical Friedmann-Lemaitre equations are solved using a corrected version of Planck’s radiation law. The function curves of the scale parameter a(t) and the variations with temperature a(T) and t(T) are given. It is shown that a reasonable cosmological evolution is only possible in case of flat spatial slices (k=0). The initial singularity… [Read more…]
October 16, 2011
Ti-Pei Li The discovery of an accelerating cosmic expansion rate implies that, in addition to the attractive gravity of matter, there exist in our universe some other form of energy (dark energy or cosmological constant) producing a repulsive force. The natural interpretation of dark energy is the vacuum energy. However, the density of vacuum energy… [Read more…]
October 14, 2011
The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect, says physicist It’s now been three weeks since the extraordinary news that neutrinos travelling between France and Italy had been clocked moving faster than light. The experiment, known as OPERA, found that the particles produced at CERN near Geneva arrived… [Read more…]
October 10, 2011
Paul H. Cox, Benjamin C. Harms, Shaoqi Hou The statistical mechanics of a gas of Einstein-Kalb-Ramond wormholes is studied in this paper. The wormholes studied are the result of sewing together two Reissner-Nordstrom-type black hole metrics at their horizons. By requiring the stress-energy tensor associated with this geometry to be that of a Kalb-Ramond field,… [Read more…]
October 7, 2011
A new type of gyroscope based on interfering atoms has been developed that can determine the latitude where the instrument is located – and also measure true north and the Earth’s rate of rotation. The device has been developed by physicists in the US, who hope to scale it up so that it can test… [Read more…]
October 7, 2011
….but super-aliens may have already beaten us to it,’ claims Russian cosmologist Most advanced civilisation in the galaxy could already be living inside, claims Vyacheslav Dokuchaev Despite being considered the most destructive force in space and absolutely uninhabitable, the conditions for life exist inside supermassive black holes, a Russian cosmologist has theorised. Going out on… [Read more…]
October 6, 2011
– It’s been just two weeks since the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) team released its announcement claiming that they have been measuring muon neutrinos moving faster than the speed of light, causing an uproar in the physics community. Since that time, many papers (perhaps as many as 30 to the preprint server arXiv… [Read more…]
October 6, 2011
Hellmut Baumgärtel The note presents a classification of the relevant distinct types of solutions of the general Friedmann equation without assuming a priori restrictions for the parameters occurring in this equation. The emphasis is on the case of a non-vanishing cosmological constant. The classification uses algebraic criteria. The result is: There are four distinct basic… [Read more…]
October 3, 2011
Suresh Kumar …… Read more: http://arxiv.org
September 28, 2011
All observations in astronomy are based on light emitted from stars and galaxies and, according to the general theory of relativity, the light will be affected by gravity. At the same time all interpretations in astronomy are based on the correctness of the theory of relatively, but it has never before been possible to test… [Read more…]
September 28, 2011
Nothing can go faster than light, right? Einstein said so. But last week a group of researchers in Italy announced that they’d measured the speed of thousands of neutrinos (tiny, almost massless particles that were fired at their detector from the CERN particle physics lab 730 kilometers away) and found they were traveling slightly faster… [Read more…]
September 25, 2011
Suppose that the result of the OPERA experiment is right and neutrinos travelling faster than light…. This is the end of Einstein’s theory of special relativity and the Lorentz transformations? Is it possible the special relativity without the second postulation; The answer is yes. Read for example: “Simple derivation of the special theory of relativity… [Read more…]
September 24, 2011
Almost all theoretical oriented physicists including myself seem to feel almost certain that there is a mistake in the Opera paper and the claimed violation of the relativistic speed limit will go away. On the other hand, I think that many people who like technology etc. were impressed by the precision work that the Opera… [Read more…]
September 24, 2011
Those working in science are accustomed to receiving emails starting with “dear sir/madam, please look at the attached file where I’m proving einstein theory wrong”. This time it’s a tad more serious because the message comes from a genuine scientific collaboration… As everyone knows by now, the OPERA collaboration announced that muon neutrinos produced at… [Read more…]
September 23, 2011
EP Seminar “New results from OPERA on neutrino properties“ by Dario Autiero (Institut de Physique Nucleaire de Lyon) Friday, September 23, 2011 from 16:00 to 18:00 (Europe/Zurich)
September 23, 2011
The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km with much higher accuracy than previous studies conducted with accelerator neutrinos. The measurement is based on high-statistics data taken by OPERA in the years 2009, 2010 and… [Read more…]
September 22, 2011
Read also: A Six-Sigma Signal Of Superluminal Neutrinos From Opera! If it’s true, it will mark the biggest discovery in physics in the past half-century: Elusive, nearly massless subatomic particles called neutrinos appear to travel just faster than light, a team of physicists in Europe reports. If so, the observation would wreck Einstein’s theory of… [Read more…]
September 22, 2011
Strong long-scale gravitational waves can explain cosmic acceleration within the context of general relativity without resorting to the assumption of exotic forms of matter such as quintessence. The existence of these gravitational waves in sufficient strength to cause observed acceleration can be compatible with the cosmic microwave background under reasonable physical circumstances. An instance of… [Read more…]
September 21, 2011
“We know that about 25% of the matter in the universe is dark matter, but we don’t know what it is,” Michael Kesden tellsPhysOrg.com. “There are a number of different theories about what dark matter could be, but we think one alternative might be very small primordial black holes.” When many of us think about black… [Read more…]
September 13, 2011
Alternatives to Einstein’s general theory of relativity can be investigated by studying the Sun. That is the claim of a group of physicists in Portugal who have found that a variation of a theory put forward nearly a century ago by Arthur Eddington is constrained but not ruled out by observations of solar neutrinos and… [Read more…]
September 11, 2011
A quantum phenomenon allows detectors which sense oscillations of space-time to measure with 50 percent more accuracy. Measuring at the limits of the laws of nature – this is the challenge which researchers repeatedly take up in their search for gravitational waves. The interferometers they use here measure with such sensitivity that a particularquantum phenomenon of light… [Read more…]
September 7, 2011
The evidence is growing that some parts of the Universe are more special than others One of the cornerstones of modern astrophysics is the cosmological principle. This is the idea that observers on Earth have no privileged view of the Universe and that the laws of physics must be the same everywhere. Many observations back… [Read more…]
September 6, 2011
We know lots about gravity in a vacuum but very little about gravity inside extremely massive objects. But astrophysicists say the Sun could reveal all Einstein’s theory of general relativity is one of the cornerstones of modern physics. As such, it is unquestionably a towering achievement. And yet it also raises uncomfortable questions for physicists. The… [Read more…]
September 5, 2011
Watch this video and learn everything you’d ever want to know about spaghettification Now here’s an interesting thought to begin your work week: death by black hole. In this convergence between biology and astrophysics, Neil deGrasse Tyson, the director of the Hayden Planetarium at the American Museum of Natural History, talks about the process of… [Read more…]
September 5, 2011
Physical research looks for clues to quantum properties of the gravitational field. On the basis of the common Schr\”odinger theory, a simple model of the quantization of a Friedmann universe comprising dust and radiation is investigated. With regard to energy quantization, the result suggests a universal limitation of the energy spacing between neighbouring quantum states… [Read more…]
September 3, 2011
We examine the ability to test the black hole no-hair theorem at the 10% level in this decade using the binary black hole in OJ287. In the test we constrain the value of the dimensionless parameter q that relates the scaled quadrupole moment and spin of the primary black hole: q2 = −q χ^2. At the… [Read more…]
August 24, 2011
The way gravity effects quantum particles proves that it cannot be an emergent phenomenon, says physicist. One of the most exciting ideas in modern physics is that gravity is not a traditional force, like electromagnetic or nuclear forces. Instead, it is an emergent phenomenon that merely looks like a traditional force. This approach has been… [Read more…]
August 24, 2011
Who discovered that E = mc2? It’s not as easy a question as you might think. Scientists ranging from James Clerk Maxwell and Max von Laue to a string of now-obscure early 20th-century physicists have been proposed as the true discovers of the mass–energy equivalence now popularly credited to Einstein’s theory of special relativity. These… [Read more…]
August 21, 2011
We discuss the observable effects of enhanced black hole mass loss in a black hole-neutron star (BH-NS) binary, due to the presence of a warped extra spatial dimension of curvature radius L in the braneworld scenario. For some masses and orbital parameters in the expected ranges the binary components would outspiral—the opposite of the behavior due to… [Read more…]
August 20, 2011
Benjamin K. Tippett In light of the surge in popularity of electromagnetic cloaking devices, we consider whether it is possible to use general relativity to cloak a volume of spacetime through gravitational lensing. A metric for such a spacetime geometry is presented, and its geometric and physical implications are explained. In general relativity, there is… [Read more…]
August 15, 2011
A black hole’s event horizon is the ultimate last-chance saloon: beyond this boundary nothing, not even light, can escape. But does this “anything” include information itself? Physicists have spent the best part of four decades grappling with the “information paradox”, but now a group of researchers from the UK thinks it can offer a solution.… [Read more…]
August 13, 2011
In a paper published in the August 12 issue of the esteemed journal Physical Review Letters, researchers at the University of York made a monumental discovery, when they found that black holes tend to gulp up all the matter in their surroundings, but leak information. The new data adds to the growing database of knowledge we have… [Read more…]
August 8, 2011
A theory of reality beyond Einstein’s universe is taking shape – and a mysterious cosmic signal could soon fill in the blanks IT WASN’T so long ago we thought space and time were the absolute and unchanging scaffolding of the universe. Then along came Albert Einstein, who showed that different observers can disagree about the… [Read more…]
July 26, 2011
Extraordinary rays in a hyperbolic metamaterial behave as particle world lines in a three dimensional (2+1) Minkowski spacetime. We analyze electromagnetic field behavior at the boundaries of this effective spacetime depending on the boundary orientation. If the boundary is perpendicular to the space-like direction in the metamaterial, an effective Rindler horizon may be observed which produces… [Read more…]
July 25, 2011
Scientists prove nothing can travel faster than the speed of light No heading Back To The Future: Scientists have proved that a single photon obeys Einstein’s theory that nothing can travel faster than the speed of light and that time travel is therefore impossible For those that while away their days dreaming about travelling… [Read more…]
July 24, 2011
Lectures General Relativity 2010 G. ‘t Hooft, T. Prokopec http://www.staff.science.uu.nl/~hooft101/
July 15, 2011
According to the conclusions of a new study, it would appear that the gigantic mass our galaxy has may contribute to underlying the asymmetry in decay rates between matter and antimatter. This phenomenon, called charge-parity (C-P) violation, has remained mysterious for years. The Milky Way has a tremendously large mass, accounted for by both normal,… [Read more…]
July 14, 2011
A brilliant physicist João Magueijo asks the heretical question: What if the speed of light—now accepted as one of the unchanging foundations of modern physics—were not constant?“A number of surprising observations made at the threshold of the 21st century have left cosmologists confused and other physicists in doubt over the reliability of cosmology,” Magueijo says.… [Read more…]
June 30, 2011
One of the main strides in the field of physics is to unite the nature of space proposed by Albert Einstein’s Theory of General Relativity with the one proposed by quantum theory. Readings collected by a telescope in Earth’s orbit are now making this effort even harder. The INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a… [Read more…]
June 28, 2011
Using a vast array of radio telescopes, astronomers in North America are the first to make a direct measurement of the distance to Cygnus X-1, allowing them to conclude that the mass of its dark star is so great it can only be a black hole. They have also discovered that the black hole spins… [Read more…]
June 21, 2011
Space is festooned with vast “hyperclusters” of galaxies, a new cosmic map suggests. It could mean that gravity or dark energy – or perhaps something completely unknown – is behaving very strangely indeed. We know that the universe was smooth just after its birth. Measurements of the cosmic microwave background radiation (CMB), the light emitted… [Read more…]
June 21, 2011
M.R.S. Hawkins The aim of this paper is to present the case that stellar mass primordial black holes make up the dark matter component of the Universe. A near critical density of compact bodies implies that most lines of sight will be gravitationally microlensed, and the paper focuses on looking for the predicted effects on… [Read more…]
June 17, 2011
Einstein taught us that the speed of light was the traffic law of the universe—nothing could go faster. The development of media in which atomic gases can slow down or speed up the passage of light pulses initially caused a stir, at least until the difference between phase velocity and group velocity could be carefully… [Read more…]
June 14, 2011
In the next decade or two, extremely accurate tests of general relativity under extreme conditions are expected from gravitational wave observations of binary black hole mergers with a wide range of mass ratios. In addition, major improvements are planned in both strong and weak equivalence principle tests; clock measurements based on the ACES program on… [Read more…]
June 13, 2011
Matej Pavsic We start from the Einstein-Hilbert action for the gravitational field in the presence of a point particle source, and cast the action into the corresponding phase space form. The dynamical variables of such a system satisfy the point particle mass shell constraint, the Hamilton and the momentum constraints of the canonical gravity. In the… [Read more…]
June 12, 2011
In recent years, UC Santa Barbara scientists showed that they could reproduce a basic superconductor using Einstein’s general theory of relativity. Now, using the same theory, they have demonstrated that the Josephson junction could be reproduced. The results are explained in a recent issue of the journal Physical Review Letters. The Josephson junction, a device… [Read more…]
June 10, 2011
David L. Wiltshire “The problems of coarse-graining and averaging of inhomogeneous cosmologies, and their backreaction on average cosmic evolution, are reviewed from a physical viewpoint. A particular focus is placed on comparing different notions of average spatial homogeneity, and on the interpretation of observational results. Among the physical questions we consider are: the nature of… [Read more…]
May 28, 2011
German researchers from the Albert Einstein Institute (AEI) say that the likelihood of detecting proposed universal patterns called gravitational waves from Earth could increase significantly if just a single new detector is installed on Earth. Thus far, these structures were not identified, but detectors are being built to do so. The expected rate of detection… [Read more…]
May 18, 2011
Scattering of black holes in 5 dimensions It may be widely believed that probing short-distance physics is limited by the presence of the Planck energy scale above which scale any information is cloaked behind a horizon. If this hypothesis is correct, we could observe quantum behavior of gravity only through a black hole of Planck mass. We… [Read more…]
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