Keyword: relativity

Nearly 40 years after it was proposed, mathematicians have settled one of the most profound questions in the study of general relativity. In a paper posted online last fall, mathematicians Mihalis Dafermos and Jonathan Luk have proven that the strong cosmic censorship conjecture, which concerns the strange inner workings of black holes, is false.“I personally view this work as a tremendous achievement — a qualitative jump in our understanding of general relativity,” emailed Igor Rodnianski, a mathematician at Princeton University.The strong cosmic censorship conjecture was proposed in 1979 by the influential physicist Roger Penrose. It was meant as a...

Observations of a trio of dead stars have confirmed that a foundation of Einstein’s gravitational theory holds even for ultradense objects with strong gravitational fields. The complex orbital dance of the three former stars conforms to a rule known as the strong equivalence principle, researchers reported January 10 at a meeting of the American Astronomical Society. That agreement limits theories that predict Einstein’s theory, general relativity, should fail at some level. According to general relativity, an object’s composition has no impact on how gravity pulls on it: Earth’s gravity accelerates a sphere of iron at the same rate as a...

PostModern Prosecutions by William Anderson Over the past four years, I have written (or cowritten with Candice E. Jackson) a number of articles dealing with the dishonesty of prosecutors in this country. The Duke NonRape case, as I see it, is a logical extension to a pattern that is so egregious that all we can do now is damage control. Justice pretty much is dead in the United States. The final blow in this death of a million blows has been the increasing use of conspiracy theories by the prosecution, something that the law forbids, but the courts let it...

UBC math and physics instructor, Ben Tippett. Credit: UBC Okanagan ================================================================================================================================= After some serious number crunching, a UBC researcher has come up with a mathematical model for a viable time machine. Ben Tippett, a mathematics and physics instructor at UBC's Okanagan campus, recently published a study about the feasibility of time travel. Tippett, whose field of expertise is Einstein's theory of general relativity, studies black holes and science fiction when he's not teaching. Using math and physics, he has created a formula that describes a method for time travel. "People think of time travel as something as fiction," says Tippett....

The speed of light in a vacuum is the ultimate cosmic speed limit. Just getting close to it causes problems: the weird distortions of Einsteinâ€™s relativity kick in, so time slows down, lengths go up, masses balloon and everything you thought was fixed changes. Only things that have no mass in the first place can reach light speed Â– photons of light being the classic example. Absolutely nothing can exceed this cosmic max.We have known about the special nature of light speed since an experiment by US physicists Albert Michelson and Edward Morley in the 1880s. They set two beams...

The physicist and author argues that cosmologists should take the concept of time more seriously and talks about becoming a “converted skeptic” on climate change. ....MULLER: The flow of time does not exist in the usual spacetime diagram of physics. Time is mysterious; in any relativistic coordinate system, it is linked to space. And yet time is different—and I mean much more than simply a sign in the metric. Time flows. Choose any coordinate system and you can stand still in space but not in time. That different behavior breaks the otherwise glorious spacetime symmetry. Moreover, there is a special...

The discovery of gravitational waves, announced earlier this year, marked the ultimate test of Einstein’s general theory of relativity. Einstein published his theory in the form of 10 abstract equations 101 years ago. The equations did away with Newton’s theory of gravity and replaced it with curved space and warped time. Within weeks, Karl Schwarzschild found a solution to Einstein’s equations. His conclusion was astonishing and almost unbelievable: it told us that time depends on altitude and that matter can create holes where space and time come to an end. A few months later, Einstein himself found a solution to...

Researchers suggesting that the speed of light varies have come up with a numerical prediction that will allow their theory to be tested. Many theories in physics are built upon the idea that the speed of light is at a constant rate, but João Magueijo and Niayesh Afshordi think otherwise. In a paper published in the journal Physical Review D, they detailed the creation of an exact figure on the spectral index, a model that can be used to determine if their theory is valid or not. All structures in the universe today were created when fluctuations occurred in the...

WWith hindsight, it seems as though scientific breakthroughs sweep quickly to universal acceptance. A paper is published and everybody says, “Eureka!” But that’s not necessarily the case. Sometimes scientists have too much invested in the status quo to accept a new way of looking at things. This was certainly true when Albert Einstein‘s 1905 paper on “special relativity” first challenged the British conception of ether. Einstein argued that space and time were bound up together (something he would elaborate on in his theory of general relativity of 1915, adding gravity to the mix of space/time), a complicated idea that contradicted...

For nearly 20 years, physicists have known that the expansion of the universe has begun to speed up. This bizarre acceleration could arise because some form of mysterious dark energy is stretching space. Or, it could signal that physicists' understanding of gravity isn't quite right. But a new study puts the screws on a broad class of alternative theories of gravity, making it that much harder to explain away dark energy. The study is also path setting because it exploits an effect called weak lensing in which the gravity from closer galaxies distorts the images of more distant ones. "That's...

The idea that our Universe is filled with dark matter has been around for nearly a century. When astronomers noticed that orbital speeds towards the edges of spiral galaxies remain the same or even increase slightly, rather than decrease, they surmised that either there must be some huge unseen mass driving the rotation, or that the laws of gravity given by Einstein's General Relativity need to be changed. They elected the first option. Over that time, cosmologists have accumulated boatloads of evidence in favor of the notion that this invisible, "dark" matter  which neither interacts with nor emits light...

The shape of a Schwarzschild black hole is that of a sphere, and so its area is $A=4\pi r_ h^2$. We might be tempted to use our ordinary intuition about geometry, and deduce that the volume of a Schwarzschild black hole must be $V=4/3 \pi r_ h^3$. This is, however, not necessarily the case. It turns out that the volume of a black hole is not a welldefined notion in general relativity. The reason is that general relativity is a geometric theory of a fourdimensional spacetime, that is, three dimensions of space and one dimension of time. In order to...

Now that LIGO has detected their first gravitational wave signal, the part of Einstein's theory that predicts that the fabric of space itself should have ripples and waves in it has been confirmed. This brings up all sorts of interesting questions, including this one from reader (and Patreon supporter!) Joe Latone, who asks: "Are gravity waves expected to exhibit waveparticle duality, and if so, have LIGO physicists already conceived of ways to test it, like the doubleslit experiment?" It started out simply enough: matter was made of particles, things like atoms and their constituents, and radiation was made of waves....

Pondering Gravitational Wavesby Paul Gilster on February 11, 2016 "Einstein would be beaming," said National Science Foundation director France CÃ³rdova as she began this morning's news conference announcing the discovery of gravitational waves. I can hardly disagree, because we have in this discovery yet another confirmation of the reality of General Relativity. Caltech's Kip Thorne, who discussed black hole mergers way back in 1994 in his book Black Holes and Time Warps, said at the same news conference that Einstein must have been frustrated by the lack of available technologies to detect the gravitational waves his theory predicted, a lack...

Scientists are claiming a stunning discovery in their quest to fully understand gravity.

There has been no announcement, no peer review or publication of the findings  all typically important steps in the process of releasing reliable and verifiable scientific research. Instead, a message on Twitter from an Arizona State University cosmologist, Lawrence Krauss, has sparked a firestorm of speculation and excitement. Krauss does not work with the Advanced Laser Interferometer Gravitational Wave Observatory, or LIGO, which is searching for ripples in the fabric of space and time. But he tweeted on Monday about the apparent shoring up of rumor he'd heard some months ago, that LIGO scientists were writing up a paper...

In a recent interview, Gaza ENT doctor Muhammad Yahya Barzaq said that he had written a book refuting Einstein's Theory of Special Relativity. "Had Einstein deigned to read the discoveries of Christian Doppler, we would never have had something called the Einstein Theory," he said. Barzaq further said that he had come up with his invention of what he called a "cartridge plane" after replacing a cassette at the exact moment when an airplane was flying overhead. On the issue of Gaza he said that people there "deserve to live because they have the benefit and interest of humanity at...

The Universe we know and love  with Einstein's General Relativity as our theory of gravity and quantum field theories of the other three forces  has a problem that we don't often talk about: it's incomplete, and we know it. Einstein's theory on its own is just fine, describing how matterandenergy relate to the curvature of spaceandtime. Quantum field theories on their own are fine as well, describing how particles interact and experience forces. Normally, the quantum field theory calculations are done in flat space, where spacetime isn't curved. We can do them in the curved space described by...

Physics is built out of philosophically fascinating ideas. Or, at least, ideas that fascinate us as physicists. We are often moved to reverentially proclaim the beauty of various concepts and theories. Sometimes this beauty makes sense to other people (we're made of star stuff) and other times it's opaque (Frobenius manifolds in psuedoEuclidean spaces). I have my own personal favorite idea. It arises from the philosophically fantastic (but mathematically moderate) workings of Einstein's relativity theory. The theory of special relativity holds that time and space are not separate entities, each operating on its own; rather they are intimately and inextricably...

Sometimes you have to think outside the box. Faced with some of the universe’s most stubborn mysteries, such as the identity of dark matter, physicists are turning to a technique that employs the weird laws of quantum mechanics: atom interferometry. Atom interferometers allow the study of various physical phenomena by splitting atom waves using a nanograting, such as this one. Composed of silicon nitride, this grating, imaged with a scanning electron microscope, has a period of 100 nm. Image courtesy of Alex Cronin (University of Arizona, Tucson, AZ). This method, which takes advantage of the fact that quantum particles behave...


