Uncertainty isn't what it used to be

One of the central planks of quantum mechanics was this week called into question in a new take on the classic two-slit experiment.

One of the central notions in quantum mechanics is that light and matter can behave as both particle and wave. The principle of "complementarity" has always been understood to prevent the observation of both behaviours simultaneously. However, new research published in Science on 2 June, suggests that physicists at the University of Toronto and Griffith University in Brisbane have for the first time observed both behaviours at the same time.

In Thomas Young's 19th century "two-slit experiment", light is passed through two tiny holes and is then viewed on a screen. The two beams interfere with each other, forming a diffraction pattern, as if the light were made of waves. If one of the slits is blocked, the light can be seen as a single beam on the screen, as if light were made of particles. The two-slit experiment shows that, depending on how it's measured, a photon will act like either a particle or a wave, but never both.

Aephraim Steinberg of the University of Toronto and Sacha Kocsis of Griffith recreated this experiment, easily observing the interference pattern indicative of the wave nature of light. But significantly, they were also able measure the path of the particles of light.

Science reporter, Adrian Cho elaborates on the importance of their new research:
"For decades, [the] experiment has served as physicists' canonical example of the uncertainty principle: the law of nature that says you can't know both where a subatomic particle is and how fast it is moving, and thus can't trace its trajectory. But now physicists have tweaked that classic experiment to show that they can follow the average path taken by many particles."

Steinberg and his team allowed photons to pass through a calcite crystal which gave each photon a small deviation in its path. By measuring the light patterns on a camera, the team was able to deduce what paths the photons had taken. They clearly saw the interference pattern which infers the wave nature of light, but surprisingly they also could see from which slits the photons had come from, a telltale sign of the particle nature of light.

Marlan Scully, a quantum physicist at Texas University, commented:

"It's a beautiful series of measurements by an excellent group, the likes of which I've not seen before.",

"This paper is probably the first that has really put this weak measurement idea into a real experimental realisation." He said that the work would - inevitably - raise philosophical issues as well. "The exact way to think about what they're doing will be researched for some time, and the weak measurement concept itself will be a matter of controversy"

Professor Steinberg commented, "I feel like we're starting to pull back a veil on what nature really is".

Source: http://news.sciencemag.org

&
http://www.sciencemag.org/content/332/6034/1170.abstract

Sail to The Moon

In one of the more poetic and outlandish stories this week, The Observer report that engineers are planning to build the first extraterrestrial boat.

They want to launch the craft towards Titan - Saturn's largest moon - and parachute it on to the Ligeia Mare, a sea of methane and ethane on its surface.

Robin McKie, Science Editor of The Observer writes, "the robot ship would sail around this extraterrestrial sea for several months, exploring its coastline and measuring the winds and waves that sweep its surface."

Professor John Zarnecki, of the Open University is one of the scientists working on the project. "Waves on Titan's seas will be far larger, but much slower, than on earthly oceans, according to our calculations. That suggests Titan is the best spot in the solar system for surfing."

The mission to Titan - the only moon in the solar system with a thick atmosphere, of nitrogen and methane - would be the first exploration of a sea beyond Earth and could provide evidence about the possible existence of complex organic chemicals, the precursors of life.

It is part of the proposed Titan Mare Explorer, or TiME project.

If TiME is selected from a shortlist of three possible missions being considered for funding by NASA, McKie explains that "the TiME probe will be fired at Titan on a billion-mile journey across the solar system. Once it enters the moon's thick atmosphere the craft would parachute down towards the surface and then drop into the 300-mile-wide Ligeia Mare. It would then spend several months afloat on an oily sea taking measurements of waves, chemicals and other variables."

It follows on from the research undertaken by Cassini-Huygens. In 2005, the space-probe, Cassini deployed Huygens on the surface of Titan. Many of the instruments for that craft were built by Zarnecki and his Open University team, and that experience will put them in good stead for the TiME mission, should it go ahead.

Full story: http://www.guardian.co.uk

Source: Titan.pdf

&: SailtoThe Moon

Can bacteria transmit radio waves?

This week arXiv published a controversial abstract positing possible evidence for electromagnetic emissions from bacterial organisms.

Whilst seemingly outlandish, this isn't a new area research. Bacterial radio waves were theorised in 2009 by French virologist Luc Montagnier, who won the Nobel Prize for medicine in 2008 for the discovery of HIV.

Montagnier's highly controversial theory suggests that solutions containing the DNA of pathogenic bacteria and viruses, including HIV, could emit low frequency radio waves that induced surrounding water molecules to become arranged into nanostructures. These water molecules, he posited, could also emit radio waves. His research is summarised in this presentation paper.

But as Physics arXiv Blog at Technology Review points out, there are few more divisive figures than Montagnier, and his claims are flatly rejected by most mainstream biologists. PZ Myers memorably condemned the research as, "an awful paper that I would have shredded in a sea of red ink if it had come to me".

So what's new about the current arXiv report, and who would stick their neck out and be associated with furthering a theory that was met with such universal bile? Allan Windom is a theorist at Northeastern University in Boston who specialises in quantum field theory at the interface between high energy theory and condensed matter theory. Along with J. Swain, Y. Srivastava, and S. Sivasubramanian, he believes he may have solved one of the most controversial problems with Montagnier's theory, ie, there is no known mechanism by which bacteria can generate radio waves.

arXiv summarise their abstract (linked to below), as follows:

"Many types of bacterial DNA take the form of circular loops. So they've modelled the behaviour of free electrons moving around such a small loop, pointing out that, as quantum objects, the electrons can take certain energy levels. [They] calculate that the transition frequencies between these energy levels correspond to radio signals broadcast at 0.5, 1 and 1.5 kilohertz. And they point out that exactly this kind of signal has been measured in E Coli bacteria. [...] It is well known that bacterial and other types of cells use electromagnetic waves at higher frequencies to communicate as well as to send and store energy. If cells can also generate radio waves, there's no reason to think they wouldn't exploit this avenue too."

This is undoubtedly going to create a stir in the biological physics community, so stay tuned for more.

Source:
http://arxiv.org/abs/1104.3113
http://www.technologyreview.com/blog/arxiv/26670/

Electron beams link Saturn with Enceladus

More exceptionally exciting new research results from NASA's highly productive Cassini mission are being published in Nature this week.

A team of researchers, lead by University College London (UCL), have revealed that Enceladus, one of Saturn's diminutive moons, is linked to Saturn by powerful electrical currents - beams of electrons that flow back and forth between the planet and moon. The UCL announcement elucidates further:

"Since Cassini's arrival at Saturn in 2004 it has passed 500km-wide Enceladus 14 times, gradually discovering more of its secrets on each visit. Research has found that jets of gas and icy grains emanate from the south pole of Enceladus, which become electrically charged and form an ionosphere. The motion of Enceladus and its ionosphere through the magnetic bubble that surrounds Saturn acts like a dynamo, setting up the newly-discovered current system."

Scientists already knew that the giant planet Jupiter is linked to three of its moons by charged current systems set up by the satellites orbiting inside its giant magnetic bubble, the magnetosphere, and that these current systems form glowing spots in the planet's upper atmosphere. The latest discovery at Enceladus shows that similar processes take place at the Saturnian system too.

The detection of the beams was made by the Cassini Plasma Spectrometer's electron spectrometer, the design and building of which was led at UCL's Mullard Space Science Laboratory. UCL co-authors of the Nature paper, Dr Geraint Jones and Professor Andrew Coates, are delighted with this new finding.

Dr Jones said: "Onboard Cassini, only Cassini Plasma Spectrometer's electron spectrometer has the capability of directly detecting the electron beams at the energies they're seen; this finding marks a great leap forward in our understanding of what exactly is going on at mysterious Enceladus."

Professor Coates, added: "This now looks like a universal process - Jupiter's moon Io is the most volcanic object in the solar system, and produces a bright spot in Jupiter's aurora. Now, we see the same thing at Saturn - the variable and majestic water-rich Enceladus plumes, probably driven by cryovolcanism, cause electron beams which create a significant spot in Saturn's aurora too."

Source: http://www.ucl.ac.uk/news/news-articles/1104/11042001

Jodrell Bank selected for Square Kilometre Array

Major news from the world of radio astronomy this week, as Jodrell Bank was chosen as the headquarters for the planning and construction of the long-awaited Square Kilometre Array radio telescope.

Set to be one of the great scientific endeavours of the 21st Century, the Square Kilometre Array (SKA) will be the world's largest and most sensitive radio telescope. Jodrell Bank beat off fierce competition from sites in Holland and Germany to be selected as the project headquarters. The SKA itself will be located in either Australia and New Zealand or Southern Africa.

The SKA will investigate fundamental unanswered questions about our Universe, including how the first stars and galaxies formed after the Big Bang, how galaxies have evolved since then, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth.

Jocelyn Bell Burnell, the eminent radio astronomer who discovered pulsars at Jodrell Bank in 1967 had this to say:
"The power of this new telescope project is going to surpass anything we've seen before, enabling us to see many more radio-emitting stars and galaxies and pulling the curtains wide open on parts of the great beyond that radio astronomers like me have only ever dreamt of exploring."

Steve Rawlings of Oxford University hopes it might explain dark energy:
"The Square Kilometre Array is a time machine. As you look out to greater distances you're seeing the universe as it was when it was younger, and so you can map out the expansion of the universe. Dark energy seems to accelerate that expansion and so we will be able to map out dark energy and perhaps discover what it is."

Rather than being a huge single radio dish, it will be made up of thousands of smaller ones, which are distributed across vast geographical areas. A large array is needed because the wavelength of radio waves is far greater than that of visible light. "In order to get the same level of detail as a good optical telescope you'd need something 100km across. Clearly you can't build a single telescope a 100km across, but what you can do is build a network of telescopes and link those telescopes together." Simon Garrington, of Jodrell Bank explains.

Set to cost an estimated 1.5 billion Euros, this huge endeavour involves more than 70 institutes in 20 countries. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity of the best current-day telescopes.

Sources:
http://www.skatelescope.org
http://www.bbc.co.uk/news/science-environment-12891215

special B mesons found at LHCb

Interesting news from the LHCb detector today. Physorg.com are carrying a story about group of scientists led by Syracuse University physicist, Sheldon Stone, who have apparently become the first to observe the decays of a rare particle - a special type of B meson - thought to be present right after the Big Bang.

Physorg.com write:
"B mesons are a rare and special subgroup of mesons composed of a quark and anti-quark. While B mesons were common after the Big Bang, they are not believed to occur in nature today and can only be created and observed under experimental conditions in the LHC or other high-energy colliders.

Sheldon Stone comments: "We know when the universe formed from the Big Bang, it had just as much matter as antimatter. But we live in a world predominantly made of matter, therefore, there had to be differences in the decaying of both matter and antimatter in order to end up with a surplus of matter."

Because these particles don't play by the same rules of physics as most other matter, scientists believe B mesons may have played an important role in the rise of matter over antimatter. The particles may also provide clues about the nature of the forces that led to this lack of symmetry in the universe.

Sheldon Stone, notes on Physorg, "we want to figure out the nature of the forces that influence the decay of these particles. These forces exist, but we just don't know what they are. It could help explain why antimatter decays differently than matter."

Source: http://www.physorg.com/news/2011-03-physicists-rare-particles-large-hadron.html

Nature Network

Particle Decelerator has joined the Nature blogosphere.

As well as being a portal to the blogs written by Nature editors and journalists, Nature Blogs aggregates posts from science blogs. We're in the P section.

Source: http://blogs.nature.com/blogs/atoz/P

Is the Universe really cloaked in invisible cloth?

This week the science blogs have been alive with conflicting views about dark matter.

Dark matter is the invisible stuff that is supposed to make up around 20% of the Universe. But not everyone is willing to buy the idea that the Universe is cloaked in "invisible cloth." Proponents of an alternative, older theory, modified Newtonian dynamics (MOND), insist theories of dark matter, may simply have no clothes.

The latest MOND vs Dark Matter discussions have been promoted by the publication of a highly controversial paper by University of Maryland astronomer, Stacy McGaugh in the Physical Review Letters, which suggests that for galaxies, MOND fits the facts more reliably than theories of dark matter.

cf: https://www.newsdesk.umd.edu

The Weizmann Wave - the blog of the Weizmann Institute, who came up with MOND in 1983 - immediately picked up on this: They wrote:

"Dark matter [...] was thought up to explain a puzzling observation. The amount of mass we can see through our telescopes is not enough to keep galaxies from spinning apart. The existence of great quantities of hidden mass would provide the gravitational pull needed to form those galaxies and enable them to rotate in the way that they do.

[But] an alternate theory, first put forward by Weizmann Institute astrophysicist Prof. Moti Milgrom in 1983, doesn't require dark matter to explain the phenomenon. Instead, it posits that gravity works differently on the intergalactic scale. With a good tweak to Newton's formula, the observed Universe falls into place. This is not the violation of a basic law of physics that it might appear: Milgrom points out that gravity works fine in our every-day world, but the formula breaks down at extremes - at the speed of light or in the sub-atomic world of quantum mechanics, for example. So super-galactic scales could be another case in which the rules of gravity simply don't apply quite as Newton wrote them.

While most are still waiting for the hunt for the mysterious dark matter to yield results, a growing minority of physicists are starting to admit that MOND (modified Newtonian dynamics) could provide a better explanation."

cf: http://scienceblogs.com/weizmann

This view is deeply controversial. Many senior researchers were quick to criticise the media feeding frenzy which surrounded the publication of McGaugh's paper:

In an article on Cosmic Variance blog, Sean Carroll noted:

"McGaugh's new paper doesn't give any evidence at all against dark matter. What it does is to claim that an alternative theory - MOND, which replaces dark matter with a modification of Newtonian dynamics - provides a good fit to a certain class of gas-rich galaxies. That's an interesting result! Just not the result the headlines would have you believe"

cf. http://blogs.discovermagazine.com/cosmicvariance

In an illuminating post on Starts With a Bang, Ethan Siegel went one step further, concluding emphatically:

"MOND was designed to work for rotating galaxies. The problem is it doesn't do anything else. And its adherents never point to anything other than rotating galaxies to support it. [...] If you want to be taken seriously as a theory, you need to do more than just the one thing you were designed to do. [...] this isn't to say that MOND isn't an interesting idea, or that the people working on it are frauds. But what's being reported is grossly misleading at best, and blatantly dishonest at worst. General Relativity could still need fixing, and there could be something else going on with gravity beyond dark matter. But we still need dark matter -- or something heretofore indistinguishable from it -- to explain all our large-scale observations."

cf: http://scienceblogs.com/startswithabang

Phil Plait's analysis on the topic on his well known Bad Astronomy blog is pretty much summed up in the title - "Dark matter is alive and well, thankyouverymuch"

cf: http://blogs.discovermagazine.com/badastronomy

But this isn't a debate which is likely to go away any time soon, so keep an eye on Science blogs for the latest ripostes in the battle of theories.

Other sources: http://news.sciencemag.org

An exquisite new instrument for listening to the Music of the Spheres

This week, the remarkable Kepler spacecraft has been in the news for the fascinating new research it is generating in detecting the size and age of stars. Kepler is using a technique that scientists dub "asteroseismology" to measure minuscule variations in a star's brightness that occur as sound-waves bounce within it.

Dr Bill Chaplin, Reader in Solar and Stellar Physics, from the University of Birmingham's School of Physics and Astronomy, spoke at the American Association for the Advancement of Science conference on Saturday 19 February 2011, giving an overview of results on the study of solar-type stars using the science of asteroseismology.

Asteroseismology is the observation of the natural resonances, or pulsations, of stars. Using the data from these oscillations, collected by the NASA Kepler spacecraft, it is possible to measure the ages and sizes of stars, and to map out their interiors with hitherto unknown precision. The Kepler Mission is primarily used to look for extrasolar planets - planets that are outside our solar system orbiting other stars, but this new finding is one of the most significant pieces of research is has yielded in recent times.

Chaplin told the conference that asteroseismology was, in essence, listening to the "music of the stars" - a somewhat poetically apt reference, given that the Kepler craft is named after the 17th century German mathematician and astronomer, Johannes Kepler who reinvigorated Pythagorus notion of the"music of the spheres".

For some time, I have been researching how radio astronomy, when used as an instrument of audification, can enable us to move closer to the "music of the spheres" (http://radioqualia.va.com.au/honor/research.html). But astroseismology is proving to be an equally powerful instrument in helping us appreciate the sonic character of our universe.

Sources:
http://v.gd/kepler
http://is.gd/chaplin

Network of radio astronomy dishes redrawing the map of our galaxy

It's been a big week for astronomy, with important new data revealing the scale of both stars and planets.

Science Daily reports on how the continent-wide Very Long Baseline Array (VLBA) - an international network of radio astronomy facilities - is redrawing the map of our home galaxy and is poised to yield tantalizing new information about extrasolar planets. Their work also has important implications for numerous areas of astrophysics, including determining the nature of dark energy, which constitutes 70 percent of the Universe.

"Solving the Dark Energy problem requires advancing the precision of cosmic distance measurements, and we are working to refine our observations and extend our methods to more galaxies," said James Braatz, of the National Radio Astronomy Observatory (NRAO).

The project uses the VLBA along with NRAO's Green Bank radio astronomy telescope in West Virginia, the largest fully-steerable dish antenna in the world. The VLBA, dedicated in 1993, uses ten, 25-meter-diameter dish antennas distributed from Hawaii to St. Croix in the Caribbean. All ten antennas work together as a single telescope with the greatest resolving power available to astronomy. Together, these telescopes can detect the faint radio emission from the stars to track their motion over time. This unique capability has produced landmark contributions to numerous scientific fields, ranging from Earth tectonics, climate research, and spacecraft navigation to cosmology.

Source: http://www.sciencedaily.com