Archive for the ‘cosmology’ category

Nov 25, 2015

Stephen Hawking’s Legacy Could Be ‘Holy Grail’ Of Physics: Combining Gravity And Quantum Mechanics At Black Hole Horizons

Posted by in categories: cosmology, neuroscience, nuclear energy, particle physics, quantum physics, sustainability


To suggest that quantum mechanics and gravity are on the verge of being reconciled would be, to the physics world at least, as significant as the discover of splitting the atom. While splitting the atom might have led to the nuclear bomb, it also led to the technology of nuclear power, i.e. nuclear fission, which, if harnessed properly, creates a renewable and sustainable energy resource. The problem has always been that quantum mechanics — the rules that govern sub-atomic particles — and gravity, the rule that governs mass as we know it (the stuff we can touch and feel), do not agree with each other. The question has always been, what is it that “unifies” these two theories? Is quantum mechanics God playing dice, as Einstein suggested?

“God doesn’t play dice with the universe.”

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Nov 23, 2015

Earth might have hairy dark matter

Posted by in category: cosmology

The solar system might be a lot hairier than we thought. A new study publishing this week in the Astrophysical Journal by Gary Prézeau of NASA’s Jet Propulsion Laboratory, Pasadena, California, proposes the existence of long filaments of dark matter, or “hairs.”

Dark matter is an invisible, mysterious substance that makes up about 27 percent of all matter and energy in the universe. The regular matter, which makes up everything we can see around us, is only 5 percent of the universe. The rest is dark energy, a strange phenomenon associated with the acceleration of our expanding universe.

Neither dark matter nor dark energy has ever been directly detected, although many experiments are trying to unlock the mysteries of dark matter, whether from deep underground or in space.

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Nov 23, 2015

Black hole batteries could power mysterious radio bursts

Posted by in category: cosmology

Just before a black hole and a neutron star collide, they may form a circuit that lights up for a few milliseconds – confirming Einstein’s theory.

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Nov 20, 2015

There Is Growing Evidence that Our Universe Is a Giant Hologram

Posted by in categories: computing, cosmology, information science, quantum physics

Old post,but interesting…

If the holographic principle does indeed describe our universe, it could help resolve many inconsistencies between relativistic physics and quantum physics, including the black hole information paradox. It would also offer researchers a way to solve some very tough quantum problems using relatively simple gravitational equations. But before we can be sure that we’re living in the Matrix, there’s still a lot of work to be done.

“We did this calculation using 3D gravitational theory and 2D quantum field theory, but the universe actually has three spatial dimensions plus time,” Grumiller said. “A next step is to generalize these considerations to include one higher dimension. There are also many other quantities that should correspond between gravitational theory and quantum field theory, and examining these correspondences is ongoing work.”

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Nov 19, 2015

Dark matter might cause fundamental constants to change over time

Posted by in categories: cosmology, particle physics

(—The fundamental constants of nature—such as the speed of light, Planck’s constant, and Newton’s gravitational constant—are thought to be constant in time, as their name suggests. But scientists have questioned this assumption as far back as 1937, when Paul Dirac hypothesized that Newton’s gravitational constant might decrease over time.

Now in a new paper published in Physical Review Letters, Yevgeny V. Stadnik and Victor V. Flambaum at the University of New South Wales in Sydney, Australia, have theoretically shown that can cause the fundamental constants of nature to slowly evolve as well as oscillate due to oscillations in the dark matter field. This idea requires that the weakly interacting dark matter particles be able to interact a small amount with particles, which the scientists show is possible.

In their paper, the scientists considered a model in which dark matter is made of weakly interacting, low-mass particles. In the early Universe, according to the model, large numbers of such dark matter particles formed an oscillating field. Because these particles interact so weakly with standard model particles, they could have survived for billions of years and still exist today, forming what we know as dark matter.

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Nov 19, 2015

Dark matter dominates in nearby dwarf galaxy

Posted by in categories: cosmology, particle physics

Dark matter is called “dark” for a good reason. Although they outnumber particles of regular matter by more than a factor of 10, particles of dark matter are elusive. Their existence is inferred by their gravitational influence in galaxies, but no one has ever directly observed signals from dark matter. Now, by measuring the mass of a nearby dwarf galaxy called Triangulum II, Assistant Professor of Astronomy Evan Kirby may have found the highest concentration of dark matter in any known galaxy.

Triangulum II is a small, faint galaxy at the edge of the Milky Way, made up of only about 1,000 stars. Kirby measured the mass of Triangulum II by examining the velocity of six stars whipping around the galaxy’s center. “The galaxy is challenging to look at,” he says. “Only six of its stars were luminous enough to see with the Keck telescope.” By measuring these stars’ velocity, Kirby could infer the gravitational force exerted on the stars and thereby determine the mass of the galaxy.

“The total mass I measured was much, much greater than the mass of the total number of stars—implying that there’s a ton of densely packed dark matter contributing to the total mass,” Kirby says. “The ratio of dark matter to luminous matter is the highest of any galaxy we know. After I had made my measurements, I was just thinking—wow.”

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Nov 13, 2015

Mysteriously quiet space baffles researchers

Posted by in categories: cosmology, physics

Astrophysicists have concluded the yet most precise search for the gravitational wave background created by supermassive black hole mergers. But the expected signal isn’t there.

Last month, Lawrence Krauss rumored that the newly updated gravitational wave detector LIGO had seen its first signal. The news spread quickly – and was shot down almost as quickly. The new detector still had to be calibrated, a member of the collaboration explained, and a week later it emerged that the signal was probably a test run.

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Nov 7, 2015

The light side of dark matter

Posted by in category: cosmology

New technology and new thinking are pushing the dark matter hunt to lower and lower masses.

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Nov 4, 2015

Hawking — Proposing a solution for the Black Hole Information Paradox

Posted by in categories: cosmology, physics

In an article published on her blog Sabine Hossenfelder suggests, not altogether tongue in cheek, that the results of a recent experiment by Jeff Steinhauer about Hawking radiation (full title of the paper “Observation of Thermal Hawking Radiation and its entanglement in an analogue black hole”) might earn a ‘return visit’ to Stockholm for Hawking in order to collect a Nobel Prize. I don’t think that Steinhauer’s work, impressive as it might seem, and as well presented as it is, will lead to any return visit to Stockholm for Stephen Hawking (or at least not anytime soon…), but I do think that a much more significant development is gathering pace that will have a far reaching effect on our understanding of the universe and provide a resolution to a long standing problem in theoretical physics thats just as important if not more important than winning a Nobel Prize.

I refer to Hawking’s brief comments made on August 25th at the Swedish Royal Institute for Technology at a conference on Hawking Radiation sponsored by the Nordic Institute for Theoretical Physic s (NORDITA). Hawking’s comments were made during the course of a short (8 minute) presentation that could well end up being the most significant scientific advance made in the century since Einstein’s paper on General Relativity was published in November 1915. That’s no small claim, but one that is increasingly looking as if it has some serious merit.

This short note describes in a little more detail why I believe this to be the case.

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Nov 2, 2015

Dumb Holes Leak

Posted by in categories: cosmology, particle physics, quantum physics

In August I went to Stephen Hawking’s public lecture in the fully packed Stockholm Opera. Hawking was wheeled onto the stage, placed in the spotlight, and delivered an entertaining presentation about black holes. The silence of the audience was interrupted only by laughter to Hawking’s well-placed jokes. It was a flawless performance with standing ovations.

In his lecture, Hawking expressed hope that he will win the Nobelprize for the discovery that black holes emit radiation. Now called “Hawking radiation,” this effect should have been detected at the LHC had black holes been produced there. But time has come, I think, for Hawking to update his slides. The ship to the promised land of micro black holes has long left the harbor, and it sunk – the LHC hasn’t seen black holes, has not, in fact, seen anything besides the Higgs.

But you don’t need black holes to see Hawking radiation. The radiation is a consequence of applying quantum field theory in a space- and time-dependent background, and you can use some other background to see the same effect. This can be done, for example, by measuring the propagation of quantum excitations in Bose-Einstein condensates. These condensates are clouds of about a billion or so ultra-cold atoms that form a fluid with basically zero viscosity. It’s as clean a system as it gets to see this effect. Handling and measuring the condensate is a big experimental challenge, but what wouldn’t you do to create a black hole in the lab?

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