4Vote!
Arxiv (Free subscription) | 11/19/2009
In this thesis, multipole expansions of mass, momentum and stress density will be made for a body in Newtonian mechanics. Using these definitions; momentum, angular momentum, center of mass, force and torque are defined for $N$ gravitationally interacting isolated bodies. Equations of motions of such a system are derived. Definitions of momentum, angular momentum, center of mass, force and torque...
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Arxiv (Free subscription) | 11/18/2009
Since the early days of the theory of electromagnetism and of gravity the idea of space, then space-time, as a sort of physical continuum hovered the scientific community. Actually general relativity shows the strong similarity that exists between the geometrical properties of space-time and the ones of a strained elastic continuum. The bridge between geometry and the elastic potential, as well in...
5Vote!
Nature (Free subscription) | 11/18/2009
Light from a distant γ-ray burst backs up a key prediction of Albert Einstein's theory of relativity — that photon speed is the same regardless of energy. But it might set the stage for evolution of the theory.
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WorldoReason (Free subscription) | 11/15/2009
What is Quantum Loop Gravity? The Quick and Dirty: A Theory of spacetime Leading proponents include: Lee Smolin, Carlo Rovelli, John Baez, Roger Penrose and Abhay Ashtekar Alternative to string theory - views space space as made up of discrete (quantised) loops that mesh together Loops are spin networks of gravitational fields that have been energized. In short: It is a quantum theory of Gravity. It...
5Vote!
Physorg (Free subscription) | 11/12/2009
(PhysOrg.com) -- A Harvard theoretical physicist has discussed with scientists at the Large Hadron Collider in Switzerland the possibility that they may discover a theorized "stau" particle, with a lifetime of a minute or so, that could provide the first experimental confirmation of string theory.
4Vote!
Arxiv (Free subscription) | 11/12/2009
One of the main challenges in theoretical physics over the last five decades has been to reconcile quantum mechanics with general relativity into a theory of quantum gravity. However, such a theory has been proved to be hard to attain due to i) conceptual difficulties present in both the component theories (General Relativity (GR) and Quantum Theory); ii) lack of experimental evidence, since the regimes...
4Vote!
Arxiv (Free subscription) | 11/12/2009
General Relativity is not the definitive theory of Gravitation due to several shortcomings which are coming out both from theoretical and experimental viewpoints. At large scales (astrophysical and cosmological scales) the attempts to match it with the today observational data lead to invoke Dark Energy and Dark Matter as the bulk components of the cosmic fluid. Since no final evidence, at fundamental...
12Vote!
Slog (Free subscription) | 11/11/2009
Slog reader Jeff Yencho just asked me to comment on this piece of news ("I read this today and thought 'geez, I'd love to hear Charles' take on this...'"): Sometime on Nov. 3, the supercooled magnets in sector 81 of the Large Hadron Collider (LHC), outside Geneva, began to dangerously overheat. Scientists rushed to diagnose the problem, since the particle accelerator has to maintain a temperature...
4Vote!
Arxiv (Free subscription) | 11/10/2009
Our universe contains a great number of extremely compact and massive objects which are generally accepted to be black holes. Precise observations of orbital motion near candidate black holes have the potential to determine if they have the spacetime structure that general relativity demands. As a means of formulating measurements to test the black hole nature of these objects, Collins and Hughes...
4Vote!
Universe Today (Free subscription) | 11/09/2009
Vitaly Ginzburg, a Russian physicist and Nobel laureate, died yesterday of cardiac arrest. He was 93 years old. Ginzburg shared the 2003 Nobel Prize in physics for his work on superconductors, but contributed to many other fields of study, including quantum theory, astrophysics, radio-astronomy and diffusion of cosmic radiation in the Earth's atmosphere. In addition, [...]
4Vote!
Arxiv (Free subscription) | 11/09/2009
The problem of cosmological particle creation for a spatially flat, homogeneous and isotropic Universes is discussed in the context of f(R) theories of gravity. Different from cosmological models based on general relativity theory, it is found that a conformal invariant metric does not forbid the creation of massless particles during the early stages (radiation era) of the Universe.
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Arxiv (Free subscription) | 11/09/2009
We investigate static spherically symmetric vacuum solutions in the IR limit of projectable nonrelativistic quantum gravity, including the renormalisable quantum gravity recently proposed by Ho\v{r}ava. It is found that the projectability condition plays an important role. Without the cosmological constant, the spacetime is uniquely given by the Schwarzschild solution. With the cosmological constant,...
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Astronomy Cmarchesin (Free subscription) | 11/06/2009
The rapidly rotating ultradense remnant of a massive star, a pulsar emits jets of radiation that sweep across space like a lighthouse beam, as shown in this illustration. For the first time, gamma-ray observations have provided clues to radio astronomers about where to find millisecond pulsars. Credit: NASA Fermi Telescope observations provide candidates to check for radio emissions By Ron Cow WASHINGTON...
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Ars Technica (Free subscription) | 11/05/2009
It was 1687 when Issac Newton first published his Philosophiæ Naturalis Principia Mathematica in which he first described his universal law of gravitation—the inverse square law that we are all taught in middle school science class. Nearly 230 years passed before Newton's law was dethroned by Albert Einstein's theory of general relativity, a theory of gravity that reconciled Newton's work...
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the evolving mind (Free subscription) | 11/05/2009
One of my favorite scenes from the sitcom, The Big Bang Theory, has two of the science nerds (Sheldon and Rajesh) working hard at tackling a tough science problem. What are they doing? Outwardly, nothing much. Just staring at a blackboard with a few strings of symbols chalked on it. Minutes [...]
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eddymkl | 02/05/2009
Leonard and Penny are drawn together after a disastrous visit from Leonard’s mother (Christine Baranski).
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waynebvc | 02/04/2009
“The Maternal Capacitance” - A disastrous visit from Mrs. Hofstadter brings Leonard and Penny closer together, on THE BIG BANG THEORY, Monday, Feb. 9 (8:00-8:30 PM, ET/PT) on the CBS Television Network.
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