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Black Holes are not as voracious as they are made out to be

August 30, 2013

I don’t understand the physics of black holes.

But I certainly had the impression that the relentless pull of gravity meant that they ruthlessly devoured everything in their paths and that they were bottomless pits. Everything beyond the event horizon – by definition – was entirely unknown and the stuff – possibly – of new Universes.

Not so – according to NASA. “Contrary to what some people think, black holes do not actually devour everything that’s pulled towards them. Sgr A* is apparently finding much of its food hard to swallow.” And so the black hole spits out what it can’t swallow!

Q. D. Wang, M. A. Nowak, S. B. Markoff, F. K. Baganoff, S. Nayakshin, F. Yuan, J. Cuadra, J. Davis, J. Dexter, A. C. Fabian, N. Grosso, D. Haggard, J. Houck, L. Ji, Z. Li, J. Neilsen, D. Porquet, F. Ripple, and R. V. Shcherbakov. Dissecting X-ray–Emitting Gas Around the Center of Our Galaxy. Science, 2013; 341 (6149): 981-983 DOI:10.1126/science.1240755

NASA Press Release:

New Chandra images of Sagittarius A* (Sgr A*), which is located about 26,000 light-years from Earth, indicate that less than 1 percent of the gas initially within Sgr A*’s gravitational grasp ever reaches the point of no return, also called the event horizon. Instead, much of the gas is ejected before it gets near the event horizon and has a chance to brighten, leading to feeble X-ray emissions.

These new findings are the result of one of the longest observation campaigns ever performed with Chandra. The spacecraft collected five weeks’ worth of data on Sgr A* in 2012. The researchers used this observation period to capture unusually detailed and sensitive X-ray images and energy signatures of super-heated gas swirling around Sgr A*, whose mass is about 4 million times that of the sun.

“We think most large galaxies have a supermassive black hole at their center, but they are too far away for us to study how matter flows near it,” said Q. Daniel Wang of the University of Massachusetts in Amherst, who led of a study published Thursday in the journal Science. “Sgr A* is one of very few black holes close enough for us to actually witness this process.”

The researchers found that the Chandra data from Sgr A* did not support theoretical models in which the X-rays are emitted from a concentration of smaller stars around the black hole. Instead, the X-ray data show the gas near the black hole likely originates from winds produced by a disk-shaped distribution of young massive stars.

“This new Chandra image is one of the coolest I’ve ever seen,” said co-author Sera Markoff of the University of Amsterdam in the Netherlands. “We’re watching Sgr A* capture hot gas ejected by nearby stars, and funnel it in towards its event horizon.”

To plunge over the event horizon, material captured by a black hole must lose heat and momentum. The ejection of matter allows this to occur.

“Most of the gas must be thrown out so that a small amount can reach the black hole”, said Feng Yuan of Shanghai Astronomical Observatory in China, the study’s co-author. “Contrary to what some people think, black holes do not actually devour everything that’s pulled towards them. Sgr A* is apparently finding much of its food hard to swallow.”

The gas available to Sgr A* is very diffuse and super-hot, so it is hard for the black hole to capture and swallow it. The gluttonous black holes that power quasars and produce huge amounts of radiation have gas reservoirs much cooler and denser than that of Sgr A*. ….

For Chandra images, multimedia and related materials, visit: http://www.nasa.gov/chandra

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Stopping the light fantastic

August 7, 2013

The speed of light in a vacuum (c) is the immutable constant. Every shadow in the world is proof absolute that it can be prevented from reaching some places (by prior reflection and absorption). But light can also be slowed-down and stopped and even stored.

Light propagates at speeds less than (c) in different media. 

In 1999, Danish physicist Lene Vestergaard Hau led a combined team from Harvard University and the Rowland Institute for Science which succeeded in slowing a beam of light to about 17 meters per second, and researchers at UC Berkeley slowed the speed of light traveling through a semiconductor to 9.7 km/s in 2004. Hau later succeeded in stopping light completely, and developed methods by which it can be stopped and later restarted.This was in an effort to develop computers that will use only a fraction of the energy of today’s machines.

Back in 2007, Lene Hau showed that light could be “stopped” and then “restarted” a little distance away.

LeneHau.jpg

Lene Hau (image photonics.com)

CAMBRIDGE, Mass., Feb. 8, 2007 — By converting light into matter and then back again, physicists have for the first time stopped a light pulse and then restarted it a small distance away. This “quantum mechanical magic trick” provides unprecedented control over light and could have applications in fiber-optic communication and quantum information processing. 

In quantum networks, information optically transmitted over the network is converted into matter, processed, and then converted back into light. The physicists at Harvard University hope that their discovery could provide a possible way to do this, since matter, unlike light, can easily be manipulated. Their findings were published this week in the journal Nature.  

“We demonstrate that we can stop a light pulse in a supercooled sodium cloud, store the data contained within it, and totally extinguish it, only to reincarnate the pulse in another cloud two-tenths of a millimeter away,” said Lene Vestergaard Hau, Mallinckrodt Professor of Physics and of Applied Physics in Harvard’s Faculty of Arts and Sciences and School of Engineering and Applied Sciences.

But now comes evidence that it can be “stopped” and stored for a whole minute – and maybe even longer.

Georg Heinze, Christian Hubrich, Thomas Halfmann. Stopped Light and Image Storage by Electromagnetically Induced Transparency up to the Regime of One Minute. Physical Review Letters, 2013; 111 (3) DOI: 10.1103/PhysRevLett.111.033601

Abstract: The maximal storage duration is an important benchmark for memories. In quantized media, storage times are typically limited due to stochastic interactions with the environment. Also, optical memories based on electromagnetically induced transparency (EIT) suffer strongly from such decoherent effects. External magnetic control fields may reduce decoherence and increase EIT storage times considerably but also lead to complicated multilevel structures. These are hard to prepare perfectly in order to push storage times toward the theoretical limit, i.e., the population lifetime T1. We present a self-learning evolutionary strategy to efficiently drive an EIT-based memory. By combination of the self-learning loop for optimized optical preparation and improved dynamical decoupling, we extend EIT storage times in a doped solid above 40 s. Moreover, we demonstrate storage of images by EIT for 1 min. These ultralong storage times set a new benchmark for EIT-based memories. The concepts are also applicable to other storage protocols.

Hugues de Riedmatten writes in Physics:

A solid-state device can now store light coherently for up to one minute.

The ability to store light while keeping its quantum coherence properties (e.g., entanglement) plays an important role in quantum information science. It makes it possible to build quantum memories for light, which could become crucial elements in many quantum information processing schemes based on the use of photons, from quantum communication networks to quantum computing protocols. A critical parameter for applications is the duration over which light can be stored. For example, the distribution of quantum bits over complex quantum information networks, and their storage for further manipulation, might require quantum memories with storage time from a few seconds to a few minutes. Writing in Physical Review Letters, Georg Heinze at the University of Darmstadt, Germany, and colleagues report an important step towards this goal by demonstrating a solid-state coherent optical memory capable of storing a classical light pulse, and even a full image, for a duration of more than one minute—the longest light-storage time reported in any system to date.

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Cosmological Principle may not hold

January 13, 2013

A new paper describes the discovery of the largest known Large Quasar Group – with a longest dimension of some 1200 Megaparsecs and a typical dimension of about 500 Mpc. (One parsec is about 3.3 light years). This LQG is thus some 1600 times longer than the distance between the Milky Way Galaxy and the Andromeda Galaxy. The research team – led by Dr Roger Clowes from UCLan’s Jeremiah Horrocks Institute – has identified the LQG which is so significant in size that it also challenges the Cosmological Principle. As Dr. Clowes remarks:

“While it is difficult to fathom the scale of this LQG, we can say quite definitely it is the largest structure ever seen in the entire universe. This is hugely exciting – not least because it runs counter to our current understanding of the scale of the universe.

“Even travelling at the speed of light, it would take 4 billion years to cross. This is significant not just because of its size but also because it challenges the Cosmological Principle, which has been widely accepted since Einstein. Our team has been looking at similar cases which add further weight to this challenge and we will be continuing to investigate these fascinating phenomena.”

And if the Cosmological Principle does not hold it means that the fundamental constants of the known Universe may no longer be so fundamental or so constant.  The list of such constants is long but the most fundamental of these on which we build our understanding of the Universe – which we take as being  immutable – are the speed of light in a vacuum, the gravitational constant and the Planck constant. This opens up the possibility that the physical constants may take different values in different parts of the Universe. They may be a function of space and time. They may change over cosmological time – and of course this could mean that the passage of time itself is not uniform. So perhaps the “arrow of time” is really a “boomerang of time”? Or it could be that what starts out as an arrow may be morphing into a boomerang or something else as time progresses (or not). The concept of time – and not only the passage of time – may vary. What if the trajectory of time could loop on itself? or proceed in the form of a double spiral? Even if the Universe is still a non-static Universe – that itself makes a static Universe – Stasis – possible. The possibilities are legion – and not only for science fiction.

Stardate would no longer be uniform – but this could explain the variation between the different series of Star Trek!

Quasar - atists impression NASA-AFP

Quasar – artists impression NASA-AFP

A structure in the early universe at z ~ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology by, Roger G. Clowes, Kathryn A. Harris, Srinivasan Raghunathan, Luis E. Campusano, Ilona K. Soechting, Matthew J. Graham, Monthly Notices of the Royal Astronomical Society, http://arxiv.org/abs/1211.6256

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Sheldon Cooper would approve – “A rock is a clock”

January 11, 2013

This is right up Sheldon Cooper’s street (not that I understand his physics which is best explained here). A new paper suggests that the wave properties of matter (as contrasted to particle physics) could be used to measure time. If every rock is a potential clock Sheldon will have to change the rules of the “scissors, paper, rock” game. In any case, I look forward to a suitably acrimonius debate between Sheldon and Leslie Winkle on the nature of time and change.

A Clock Directly Linking Time to a Particle’s Mass, by Shau-Yu Lan, Pei-Chen Kuan, Brian Estey, Damon English, Justin M. Brown, Michael A. Hohensee and Holger Müller, Science DOI: 10.1126/science.1230767

Science Daily reports:

Taking advantage of the fact that, in nature, matter can be both a particle and a wave, he (Holger Müller, assistant professor of physics at the University of California, Berkeley) has discovered a way to tell time by counting the oscillations of a matter wave. A matter wave’s frequency is 10 billion times higher than that of visible light.

“A rock is a clock, so to speak,” Müller said.

In a paper appearing in the Jan. 11 issue of Science, Müller and his UC Berkeley colleagues describe how to tell time using only the matter wave of a cesium atom. He refers to his method as a Compton clock because it is based on the so-called Compton frequency of a matter wave. ……

…… While Müller’s Compton clock is still 100 million times less precise than today’s best atomic clocks, which employ aluminum ions, improvements in the technique could boost its precision to that of atomic clocks, including the cesium clocks now used to define the second, he said.

“This is a beautiful experiment and cleverly designed, but it is going to be controversial and hotly debated,” said John Close, a quantum physicist at The Australian National University in Canberra. “The question is, ‘Is the Compton frequency of atoms a clock or not a clock?’ Holger’s point is now made. It is a clock. I’ve made one, it works.”

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Physics Nobel today – update — awarded to Haroche and Wineland

October 9, 2012

UPDATE 2!

Well the rumours were wrong and the prize has been awarded to Serge Haroche of France and David Wineland of the US.

UPDATE: There is a rumour doing the rounds in Sweden this morning that the Physics prize will go to Alain Aspect of France and Anton Zeilinger of Austria.

============================================

There is still some speculation that the Physics Nobel to be announced today could go to Higgs and CERN scientists for the much-hyped,  “non-discovery” of the Higgs Boson but somehow I doubt it.

 Thomson Reuters proposes three possible winners:

1. Charles H. Bennett, Gilles Brassard and William K. Wootters

For their pioneering description of a protocol for quantum teleportation, which has since been  experimentally verified

2. Leigh T. Canham

For discovery of photoluminescence in porous silicon

 3.Stephen E. Harris and Lene V. Hau

For the experimental demonstration of electromagnetically induced transparency (Harris) and of  ‘slow light’ (Harris and Hau)

There is an outside chance that it may be awarded for work straddling Physics and Chemistry – in the world of  nano-particles perhaps.

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Are numbers discrete and time continuous? or is it the other way around?

October 6, 2012

Idle thoughts and unanswerable questions on a Saturday morning:

The Number System seems to be continuous and infinite but every number seems to be discrete. But if any number is also  infinitely divisible  it must also be continuous. So are numbers simultaneously both discrete and continuous?

Or is a number just a label? Perhaps a number – if  just a label and representing a singularity – is discrete and the divisibility of a number is actually undefined. It is number difference – not a number –  which is infinitely divisible. So – for example –  the number 10, as a label, is not divisible — it is the number difference between 10 and some reference number (10-0) which is. So is our Number System then a discrete thing and made up of an infinite and continuous quantity of  number differences  with each number difference being discrete? It would then be rational for there to be an infinity of discrete Number Systems.

So perhaps numbers don’t exist.  Only number differences do and the numbers are their labels.

(more…)

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Uncertainty in the Uncertainty Principle could give certainty of observation – perhaps

September 8, 2012

Heisenberg probably rules – OK?

I first saw this as graffiti in the 1970’s – at University in the UK  and at pubs around the University. But it seems that there are areas of doubt surrounding the Heisenberg Uncertainty Principle and – by extension – around some of the basic tenets of quantum mechanics. The “observer effect” where the observation itself alters the observation may be uncertain. The question is whether uncertainty of uncertainty can lead to certainty.

Phys. Rev. Lett. 109, 100404 (2012) 

Violation of Heisenberg’s Measurement-Disturbance Relationship by Weak Measurements by Lee A. Rozema, Ardavan Darabi, Dylan H. Mahler, Alex Hayat, Yasaman Soudagar, and Aephraim M. Steinberg  DOI: 10.1103/PhysRevLett.109.100404

Dilbert on uncertainty – from United Features Syndicate Inc.

 A synopsis by David Voss in the APS

When first taking quantum mechanics courses, students learn about Heisenberg’s uncertainty principle, which is often presented as a statement about the intrinsic uncertainty that a quantum system must possess. Yet Heisenberg originally formulated his principle in terms of the “observer effect”: a relationship between the precision of a measurement and the disturbance it creates, as when a photon measures an electron’s position. Although the former version is rigorously proven, the latter is less general and—as recently shown—mathematically incorrect. In a paper in Physical Review Letters, Lee Rozema and colleagues at the University of Toronto, Canada, experimentally demonstrate that a measurement can in fact violate Heisenberg’s original precision-disturbance relationship.

(more…)

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The “luminiferous aether” has morphed to “dark matter” but we still don’t know why an apple falls…

August 12, 2012

A new paper claims to have found evidence of dark matter near the sun.

“We are 99% confident that there is dark matter near the Sun,” says the lead author Silvia Garbari. In fact, if anything, the authors’ favoured dark matter density is a little high: they find more dark matter than expected at 90% confidence. There is a 10% chance that this is merely a statistical fluke, but if future data confirms this high value the implications are exciting as Silvia explains: “This could be the first evidence for a “disc” of dark matter in our Galaxy, as recently predicted by theory and numerical simulations of galaxy formation, or it could mean that the dark matter halo of our galaxy is squashed, boosting the local dark matter density.”

But I cannot help thinking that “dark matter” and “dark energy” are no different  conceptually to the theories of phlogiston and luminiferous aether . They are plausible artefacts created to explain observations but are not themselves observable. I am not particularly convinced when

(more…)

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Higgs Boson may not have been found after all. Just a PR exercise?

July 12, 2012

Is this some new way to ensure that funding continues?

First some very high profile publicity to announce some fantastic new discovery – which then gradually gets debunked over the next few months but at a much lower level of interest. But the initial high-profile announcements probably help to maintain the perceptions necessary to ensure funding. The low profile debunking does not register. It seems to be getting to be a habit for CERN.

Last September the CERN PR apparatus went into overdrive with the announcements that FTL neutrinos may have been found. FTL particles were announced with great fanfare only to be debunked later. And by November the story had died but the publicity had no doubt helped to bolster the perception that CERN is important.

A few days ago the CERN PR operations went into full swing. Advance warnings of an “Important Announcement” were disseminated widely. Background information was spread to all the media. Physicists around the world were interviewed about what the Higgs Boson was and what the discovery would mean. It was not long before the new “discovery” was being hailed as “the most important scientific discovery of the 21st Century, and on par with Copernicus’s discovery that the sun is the center of our solar system”.  And now just one week later it appears that whatever was found may not be the Higgs Boson and may not even be a separate particle at all.

I am naturally cynical about the extravagant trappings that sometimes surround “big science” but lately CERN’s PR seems more impressive than any physics they do:

CERN PR in action: Rolf Heuer, CERN Director General (C), Fabiola Gianotti, ATLAS experiment spokesperson (L), and Joe Incandela, a spokesman of the CMS experiment, look at a screen during a scientific seminar to deliver the latest update in the search for the Higgs boson at the European Organization for Nuclear Research (CERN) in Meyrin near Geneva July 4, 2012. REUTERS/Denis Balibouse

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CERN OPERA’s FTL neutrinos are rejected by CERN ICARUS scientists

November 21, 2011

OPERA is one set of experiments at CERN’s Italian partner labs at Gran Sasso and ICARUS is another.

image: http://www.redorbit.com

In September Opera reported the FTL neutrinos to widespread scepticism, wonder and some delight. Last Friday the OPERA scientists reported that new experiments supported the September results.

But on Saturday the ICARUS scientists reported – also on the same website-  that they had analysed the September results and that they do not stand up!!!

A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS

Reuters reports:

An international team of scientists in Italy studying the same neutrino particles colleagues say appear to have travelled faster than light rejected the startling finding this weekend, saying their tests had shown it must be wrong.

(more…)

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