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Category: physics – Page 307

For the first time, researchers have achieved superconductivity — the phenomenon of electrical conductivity with zero resistance — in a material that’s not a superconductor.

The new technique demonstrates a concept that was first proposed back in the 1970s, but until now had never been proven, and it could lead to ways to make existing superconductors, like the ones used in MRI machines or maglev trains, cheaper and more efficient at higher temperatures.

“Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known,” said lead researcher Paul C. W. Chu from the University of Houston.

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For decades, physicists searched in vain for evidence of gravitational waves, the stretches and squeezes in spacetime that were first predicted by Albert Einstein’s theory of general relativity a century ago. Even Einstein himself was uncertain that they existed. But then, in February and June of this year, scientists detected two events that produced gravitational waves.

Now that gravitational-wave detection is likely becoming a regular occurrence—we’ll probably find evidence of many more in the next few years—physicists are again pondering an obscure detail about gravitational waves that was once also thought virtually impossible to observe—gravitational-wave memory, which involves permanent changes in the distance between two objects.

“For so many years, people were simply concentrating on making that first detection of gravitational waves,” says Paul Lasky, and astrophysicist at Monash University in Australia. “Once that first detection happened, our minds have become focused on the vast potential of this new field.”

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According to our best understanding of the Universe, if you travel back in time as far as you can, around 13.8 billion years or so, you’ll eventually reach a singularity — a super-dense, hot, and energetic point, where the laws that govern space-time breakdown.

Despite our best attempts, we can’t peer past that singularity to see what triggered the birth of our Universe — but we do know of only one other instance in the history of our Universe where a singularity exists, and that’s inside a black hole. And the two events might have more in common than you’ve ever considered, as physicist Ethan Siegel explains over at Forbes.

It might sound a little crazy, but, as Siegel reports, from a mathematical perspective, at least, there’s no reason that our own Big Bang couldn’t have been the result of a star collapsing into a black hole in an alternate, four-dimensional universe.

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Researchers at the universities of Valencia and Florence propose an approach to the experimental data generated by the Large Hadron Collider that solves the infinity problem without breaching the four dimensions of space-time.

The theories currently used to interpret the data emerging from CERN’s Large Hadron Collider (LHC), which have so far most notably led to the discovery of the Higgs boson, are poorly defined within the four dimensions of space-time established by Einstein in his Theory of Special Relativity. In order to avoid the infinities resulting from the calculations that these theories inspire, new dimensions are added in a mathematical trick which, although effective, does not reflect what we now know about our Universe.

Now though, a group of researchers at the Institute of Corpuscular Physics (IFIC, CSIC-UV) in Valencia has devised a way to side-step the infinity issue and keep the theory within the bounds of the four standard dimensions of space-time.

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Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late 1990s, that the universe is expanding at an accelerating pace. Their conclusions were based on analysis of Type Ia supernovae — the spectacular thermonuclear explosion of dying stars — picked up by the Hubble space telescope and large ground-based telescopes. It led to the widespread acceptance of the idea that the universe is dominated by a mysterious substance named ‘dark energy’ that drives this accelerating expansion.

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I know, it doesn’t seem like there’s any possible way that a transmission system could be interesting enough that we’d dedicate an entire article (and video!) to it. But here we are: As soon as SRI explained how their new Abacus transmission worked, we were absolutely sure that it was cool enough to share. In a nutshell, here’s why: It’s the first new rotary transmission design since Harmonic Drive introduced its revolutionary gear system in the 1960s*, and it might give harmonic gears a literal run for their money.

The physics of most electric motors generally dictates that the motors are happiest when they’re spinning very fast. Unless you want to use them to simply spin a thing very fast, you’ll need to add a rotary transmission that can convert low torque, high speed rotation into higher torque, lower speed rotation. If you’ve got the budget, the way to do this is with a high-performance harmonic gear like the ones offered by Harmonic Drive. Roboticists like harmonic gears because they are compact, have high gear ratios, and, perhaps most important, don’t have backlash, which is essentially the amount of wiggle room that you get with conventional gear-based transmissions. In robotic applications, wiggling means that you don’t know exactly where everything is all the time, making precision tasks something between irritating and impossible.

Harmonic gears are great, but they’re also superduper expensive, because they require all kinds of precision machining. Alexander Kernbaum, a senior research engineer at SRI International, has come up with an entirely new rotary transmission called the Abacus drive, and it’s a beautiful piece of clever engineering that offers all kinds of substantial advantages:

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How, then, could we tell a gravastar from a black hole? It would be almost impossible to “see” a gravastar, because of the same effect that makes a black hole “black”: any light would be so deflected by the gravitational field that it would never reach us. However, where photons would fail, gravitational waves can succeed! It has long since been known that when black holes are perturbed, they “vibrate” emitting gravitational waves. Indeed, they behave as “bells”, that is with a signal that progressively fades away, or “ringsdown”. The tone and fading of these waves depends on the only two properties of the black hole: its mass and spin. Gravastars also emit gravitational waves when they are perturbed, but, interestingly, the tones and fading of these waves are different from those of black holes. This is a fact that was alreadyknown soon after gravastars were proposed.

After the first direct detection of gravitational waves that was announced last February by the LIGO Scientific Collaboration and made news all over the world, Luciano Rezzolla (Goethe University Frankfurt, Germany) and Cecilia Chirenti (Federal University of ABC in Santo André, Brazil) set out to test whether the observed signal could have been a gravastar or not.

When considering the strongest of the signals detected so far, i.e. GW150914, the LIGO team has shown convincingly that the signal was consistent with the a collision of two black holes that formed a bigger black hole. The last part of the signal, which is indeed the ringdown, is the fingerprint that could identify the result of the collision. “The frequencies in the ringdown are the signature of the source of gravitational waves, like different bells ring with different sound”, explains Professor Chirenti.

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Physicists on the Borexino neutrino experiment at Italian physics laboratory INFN in Gran Sasso announced in Nature that they have detected neutrinos produced deep inside the sun.

Neutrinos, which constantly stream through us, interact very rarely with other matter. When created in nuclear reactions inside the sun, they fly through dense solar matter in seconds and can reach the Earth in eight minutes.

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In Brief:

Researchers have proposed an alternative way to generate super-strong magnetic fields that would solve the hindrances keeping us from harnessing the Faraday effect to its full use. More research and experimentation are needed to test the method.

In the quest to harness the powers of the Faraday effect, which would allow better control and management of nuclear fusion as well as astrophysical processes in laboratories, researchers propose a new way to generate stronger magnetic fields.

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