Archive for the ‘Fightin’’ Category

The neglected puzzle of low energy nuclear reactions

Friday, October 10th, 2008

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Cold fusion won’t go away and perhaps rightly so. Numerous groups have reported idiosyncratic behaviour of palladium hydrides sitting in heavy water when a current passes through them. Many of these experiments are said to be repeatable.

Of course, serious questions remain over what exactly is going on in these experiements. They may or may not involve fusion but either way, something interesting will have to be dreamt up to explain many of the results.

These days cold fusion goes by the name of LENR (low energy nuclear reactions). And Allan Widom from Northeastern University in Boston and a couple of mates have taken the trouble to spell out how they think the electroweak force may be behind one class of these reactions.

They say that the well known decay of a neutron into a proton and an electron is mediated by the electroweak force. And that the reaction can be reversed to turn electrons and protons into neutrons, a process that would also result in nuclear transmutation, which in turn my be responsible for the release of excess heat and of nuclear by-products. Both of these things are claimed to be seen in LENR experiments.

Surely it’s time we bury the hatchets on this one and start working out exactly what is going on in LENRs. No?

Ref: arxiv.org/abs/0810.0159: A Primer for Electro-Weak Induced Low Energy Nuclear Reactions

The remarkable language of Vai

Monday, October 6th, 2008

vai-language.jpg

Vai is a language spoken by 150,000 people in western Africa, specifically in Liberia and Sierra Leone. The language is noteworthy because its uses a remarkable system of sounds. Speakers must be able to pronounce seven oral vowels, five nasal vowels and 31 consonants all of which come in various combinations. In its written form, Vai has 229 characters.

So perhaps it wouldn’t be surprising if Vai had some interesting statistical characteristics not shared by other languages. If so, that might give some insight into the language’s unique history and evolution. This week, Charles Riley at Yale University and a few pals make exactly that claim.

Their analysis focuses on the the written form of Vai and the complexity of the characters in its alphabet. The complexity of a character is a measure of how difficult it is to draw. For example, the letter ‘O’ consists of two arches connected by two line sections which, using the strange arithmetic of character complexity, gives it a complexity of 8. The letter ‘X’ which is two straight lines that cross, has a complexity of 7.

By contrast, most characters in Vai have a complexity of more than 20 and one letter has a complexity of 48.

In all languages analysed to date, the complexity of characters is governed by an overarching rule which is that it is uniformly distributed. That means that there should be roughly equal numbers of characters with similar complexities. That’s true whether the language be Latin, Cyrillic and Runic scripts.

But Vai turns out to be different, says Riley and co. The complexity of the Vai alphabet is a better fit to a Poisson distribution rather than a uniform distribution.

So does that mean there is something special about Vai that sets it apart from other languages?

Maybe. The authors say non-uniform complexity is probably the result of the way the language was first written down in the mid-19th century. Riley and co suggest that this may have been influenced by a Cherokee native American who lived in an American mission in the area at the time.

Cherokee was famously first written down by a tribesman named Sequoyah who had seen western script without knowing what it mean. He then wrote out a similar looking script in which each sign represented a Cherokee syllable.

The clear, if improbably, implication by Riley and pals is that Vai was written down in the same way.

There are two problems with this analysis. First, as far as I know, Cherokee has not been subjected to this kind of analysis. If it has a uniform distribution, this idea is scuppered.

Second, what the authors fail to take into account is that although the alphabet has 229 characters, there is a large amount of redundancy and only 100 or so are in common usage.

When the analysis is redone using only these common characters, I wouldn’t mind betting that a uniform distribution of complexity emerges.

Which means that Riley and co have a little work to do before they take their analysis of Vai any further down this little backwater of linguistics

Ref: arxiv.org/abs/0810.0200: Distribution of Complexities in the Vai script

How politics manipulates science

Tuesday, September 30th, 2008

In a fascinating and controversial paper, Richard Lindzen from the Massachusetts Institute of Technology sets out to show how changes in the structure of scientific activity over the past half century have left the scientific endeavor vulnerable to political manipulation.

In particular, he focuses on how political bodies try to control scientific institutions, how scientists adjust both data and even theory to accommodate politically correct positions, and how opposition to these positions is disposed of.

Much of Lindzen’s discussion is aimed at the climate change debate where he says these vulnerabilities have been exploited to a remarkable extent.

As a result, he says: “progress in climate science and the actual solution of scientific problems in this field have moved at a much slower rate than would normally be possible.”

That may lead to trouble ahead.  He says that society is undoubtedly aware of the imperfections of science but it has rarely encountered a situation such as the current global warming hysteria where institutional science has so thoroughly committed itself to policies which call for massive sacrifices in well being world wide.

And he hints that this may not be best way forward. Lindzen says that massive crash programs such as the Manhattan Project are not appropriate to all scientific problems. In particular, such programs are unlikely to be effective in fields where the basic science is not yet in place. Rather, they are best suited to problems where the needs are primarily in the realm of engineering.

For the record, Lindzen was once a member of the UN’s International Panel on Climate Change and is widely regarded as a climate change skeptic.

Be that as it may, this is a recommended read.

Ref: arxiv.org/abs/0809.3762: Climate Science: Is it Currently Designed to Answer Questions?

Forget black holes, could the LHC trigger a “Bose supernova”?

Monday, September 29th, 2008

lhc-higgs

The fellas at CERN have gone to great lengths to reassure us all that they won’t destroy the planet (who says physicists are cold hearted?).

The worry was that the collision of particles at the LHC’s high energies could create a black hole that would swallow the planet. We appear to be safe on that score but it turns out there’s another way in which some people think the LHC could cause a major explosion.

The worry this time is about Bose Einstein Condensates, lumps of matter so cold that their constituents occupy the lowest possible quantum state.

Physicists have been fiddling with BECs since the early 1990s and have become quite good at manipulating them with magnetic fields.

One thing they’ve found is that it is possible to switch the force between atoms in certain kinds of BECs from positive to negative and back using a magnetic field, a phenomenon known as a Feschbach resonance.

But get this: in 2001, Elizabeth Donley and buddies at JILA in Boulder, Colorado, caused a BEC to explode by switching the forces like. These explosions have since become known as Bose supernovas.

Nobody is exactly sure how these explosions proceed which is a tad worrying for the following reason: some clever clogs has pointed out that superfluid helium is a BEC and that the LHC is swimming in 700,000 litres of the stuff. Not only that but the entire thing is bathed in some of the most powerful magnetic fields on the planet.

So is the LHC a timebomb waiting to go off? Not according to Malcolm Fairbairn and Bob McElrath at CERN who have filled the back of a few envelopes in calculating that we’re still safe. To be doubly sure, they also checked that no other superfluid helium facilities have mysteriously blown themselves to kingdom come.

“We conclude that that there is no physics whatsoever which suggests that Helium could undergo
any kind of unforeseen catastrophic explosion,” they say.

That’s comforting and impressive. Ruling out foreseen catastrophies is certainly useful but the ability to rule out unforeseen ones is truly amazing.

Ref: arxiv.org/abs/0809.4004: There is no Explosion Risk Associated with Superfluid Helium in the LHC Cooling System

Loophole found in quantum cryptography photon detectors

Tuesday, September 23rd, 2008

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If you’re hoping to secure your data using quantum cryptography, you might want to find a shoulder to cry on.

Quantum cryptography ought to be 100 percent secure. In theory , it provides perfect security against eavesdroppers. But in practice, a number of loopholes have emerged (see here and here). And today, Vadim Makarov and pals at the Norwegian University of Science and Technology reveal another.

One crucial piece of kit that every quantum cryptographer needs is a detector capable of spotting single photons. And the detector of choice in about half of quantum cryptography experiments is the Perkin Elmer SPCM-AQR detector module. “Until recently, this has been the only commercially available Si single photon detector model,” say Makarov and buddies.

Sadly, it turns out to have a significant flaw. The Norwegian team says that bombarding the machine with bright optical pulses can override the control circuitry in a way that allows an eavesdropper to control its output. That gives Eve a way of staging a successful intercept attack.

I know what you’re thinking: why not switch to the gear used in the other half of quantum crypto experiments? The answer is that Makarov and pals have already shown that these devices have a vulnerability.

All is not lost, however. Now that the vulnerability has been revealed it should be straightforward to implement extra security to foil such an attack.

But the implications are clear. The eternal cat and mouse game between eavesdroppers and their victims looks set to continue. Which means that quantum cryptography may never be perfect.

Ref: arxiv.org/abs/0809.3408: Can Eve control PerkinElmer actively-quenched single-photon detector?

Could life have come from other stars?

Thursday, September 4th, 2008

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Late in the last century, researchers calculated that an asteroid impact on Mars could jettison rocks  towards Earth in a way that preserved bacterial life within them; the implication being that life could have evolved first on a warmer wetter Mars and later seeded life on Earth.

Now Mauri Valtonen from Turku University in Finland and colleagues have worked out whether bacteria might have been able to make a similar journey from a planet orbiting another star.The answer is probably not.

But there is with one important caveat.The sun almost certainly formed in a star-birthing nursery with various other stars which later dispersed. It’s quite possible, say the team, that bacteria could have passed from one system to another while all these star systems were close together.

Nobody knows which stars are the sun’s sisters and brothers but various groups are looking to solve this conundrum. In particular, the  European Space Agency’s Gaia observatory (launch date 2011)  is designed to create a 3D map of our galaxy that should allow us to work out what came from where. Studying these stars will then become an obsession for various astronomers.

Equally likely, of course, is the possibility that Earth seeded planets around these stars with life.So if you work on Gaia, don’t be surprised to find somebody staring right back at us.

Ref:arxiv.org/abs/0809.0378 : Natural Transfer of Viable Microbes in Space from Planets in the Extra-Solar Systems to a Planet in our Solar System and Vice-Versa

Orbiting observatory finds dark matter, but what kind?

Monday, September 1st, 2008

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The world of cosmology is abuzz with rumours that an orbiting observatory called PAMELA has discovered dark matter. Last month, the PAMELA team gave a few selected physicists a sneak preview of their results at a conference in Stockholm.

Here’s the deal. The PAMELA people  say their experiment has seen more positrons than can be explained by known physics and that this excess exactly matches what dark matter particles would produce if they were annihilating each other at the center of the galaxy.

What makes this particularly exciting is that other orbiting observatories have also seen similar, but less clear cut, evidence of dark matter annihilations.

Since then, the shutters have come down. With the prospect of a major discovery on their hands  and with publication in a major journal at stake, the team has closed ranks to re-analyse their data and prepare it for exclusive publication. Not a word has leaked from the PAMELA team since their preliminary announcement.

That hasn’t stopped physicists speculating for themselves. Today Marco Cirelli from the CEA near Paris in France and Alessandro Strumia from the Università di Pisa in Italy present their own analysis of the PAMELA data.

Cosmologists have long speculated on the nature of dark matter and dreamt up all manner of models and particles to explain it. The big question is which type of particle does the PAMELA data point towards.

Today, Cirelli and Strumia stake their own claim. They say the data agrees with their own model called Minimal Dark Matter in which the particle responsible is called the “Wino” (no, it  really is called the wino).

But given the PAMELA team’s reluctance to publish just yet, where did Cirelli and Strumia get the data? The answer is buried in a footnote in their paper.

“The preliminary data points for positron and antiproton fluxes plotted in our figures have been extracted from a photo of the slides taken during the talk, and can thereby slightly differ from the data that the PAMELA collaboration will officially publish.”

Can’t fault them for initiative.

Ref: arxiv.org/abs/0808.3867: Minimal Dark Matter Predictions and the PAMELA Positron Excess

Why aluminum should replace cesium as the standard of time

Monday, August 25th, 2008

micromagic-clock

The second is defined as 9,192,631,770 vibrations of a cesium atom and measured in a device known as a fountain clock. These work by cooling a tiny cloud of cesium atoms to a temperature close to zero, tossing it up in the air and zapping it with microwaves as it falls.

Then you watch the cloud to see if it fluoresces. This fluorescence is maximised when the microwave frequency matches a hyperfine transition between two electronic states in the atoms, at exactly 9,192,631,770 Hz.

Various labs around the world use this method to run clocks with an accuracy of around 0.1 nanoseconds per day. That’s impressive but not perfect. Fountain clocks have one drawback: the clouds of cesium tend to disperse quickly and that limits how accurately you can take data.

Now there’s a new kid on the block which looks as if it’s going to be better at keeping time.

Today some chaps from the the University of Nevada in Reno and the University of New South Wales in Sydney outline a new clock that relies on an effect called the Stark shift in which a spectral line is split by an electric field (this is the electric analogue of the Zeeman effect in which spectral lines are split with a magnetic field).

This is a complex phenomenon but the key thing is that the same electric field can influence the split in different ways. In fact, a couple of groups have recently discovered that in certain circumstances these can cancel out each other at specific “magic” frequencies of an electric field. When that happens, the line splitting vanishes.

This should be pretty straightforward to measure. The electric field is supplied by trapping the atoms in a standing electromagnetic wave, otherwise known as a standard optical lattice. Then change the laser frequency while looking at the atomic spectra. When the line splitting vanishes, you’ve hit the magic frequency.

The big advantage of this method is that you can trap millions of atoms easily in an optical lattice and that should make such a clock much more robust than a fountain, while achieving at least the same kind of accuracy.

So what kind of atom should we choose to sit at the heart of these “micromagic clocks”? The Ozzie-American group says that, contrary to previous reports, cesium does not have a magic frequency and so can’t be used in this technique. Aluminum, on the other hand, should be perfect.

The second is dead, long live the second.

Ref: arxiv.org/abs/0808.2821: Micromagic Clock: Microwave Clock Based on Atoms in an Engineered Optical Lattice

Global warming and the climate of fear

Wednesday, July 2nd, 2008

It does, however, seem difficult to believe that our species, that has dominated the planet for a relatively short period of time, could have such a huge impact on our planet’s climate, whilst the Sun, the most massive body in the solar system whose influence dominates our planet, could have such little impact.

So concludes Jeremy Dunning-Davies at the University of Hull in the UK in a paper discussing the various possible causes of climate change, including the influence of the Sun.

Dunning-Davies also says that a climate of fear has descended over the global warming issue that makes it hard to debate the science behind it in a reasonable way.

That’s a sorry state of affairs. Partly because the alternative hypothesis must alway be given the oxygen of open discussion. But not least because it means we’re going to miss something important when somebody, somewhere is afraid to speak up at the right time.

Ref: arxiv.org/abs/0806.3418: Some Comments on the Possible Causes of Climate Change

The latest social network: binge drinking

Monday, June 23rd, 2008

Binge drinking

Binge drinking is “the rapid consumption of large amounts of alcohol, especially by young people, leading to serious anti-social and criminal behavior in urban centres,” say Paul Ormerod, an economist at Volterra Consulting in London, also linked to the University of Durham.

Binge drinking is a growing problem in city centers in the UK, with some 1.5 million binge drinking “events” across the country each week. Ormerod says:

“Vomiting, collapsing in the street, shouting and chanting loudly, intimidating passers-by and fighting are now regular night-time features of many British towns and cities. A particularly disturbing aspect is the huge rise in drunken and antisocial behaviour amongst young females.”

You know who you are. But why has this behavior spread so rapidly?

Ormerod and his mate Greg Wiltshire point to an interesting study of patterns of health conducted in the US, in which people were found to be much more likely to become obese if they had an outsize  friend or to stop smoking if their spouse had also stopped. Perhaps a similar kind of pattern occurs in binge drinkers, Ormerod reasoned.

To find out, he commissioned a survey of Britain’s youth, 504 18-24 year-olds, in which he asked them about their drinking patterns and those of their friends, family and colleagues.

The results are striking.  It turns out that:

  • 30 per cent of binge drinkers think that ‘all’ or ‘almost all’ of their work colleagues binge drink, compared to only 8 per cent of non-binge drinkers.
  • 54 per cent of binge drinkers think that “all” or “almost all” of their friends are binge drinkers, compared to 15 per cent of non-binge drinkers for whom “all” or “almost all” friends are binge drinkers.
  • only 3 per cent of binge drinkers have “no” or “hardly any” friends that binge drink compared to 19 per cent of non-binge drinkers.

Clearly the behaviour of people you know is linked in a significant way to your drinking habits.

Ormerod then used the data to determine that the kind of network that best describes the way these people are linked is a small world:  a network in which people are linked by a small number of steps in the manner of six degrees of separation.

And if that’s the case, binge drinking is a fashion that must be spreading like like tie-dyed T-shirts and nose studs.

That’s interesting because the fact that this is a small world network could have important implications for how to tackle the problem.

One line of thought has focused on individuals who are linked to a large number of others. These so-called hubs can have a disproportionate effect on the spread of behaviours and so targeting them would be one way to halt the spread of binge drinking.

For example, it may be that the behaviour of film stars or other widely known figures can have a disproportionate effect on the behaviour of others.

But that doesn’t seem to be the case with binge drinking. Hubs only exist in scale free networks in which the distance between people varies as a power law (so the network looks the same regardless of the resolution at which you view it).

If Ormerod’s conclusion is confirmed (he needs more data to nail it) and the pattern of binge drinking in the UK really do reflect a small world network, then this kind of targeting is unlikely to work.

Ref: arxiv.org/abs/0806.3176: ‘Binge’ Drinking in the UK: a Social Network Phenomenon