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Home » Page 1403

Snake venom gets into the groove

If you are ever unlucky enough to have a snake sink its fangs into your leg, then you might take a second to marvel at the clever mechanism behind its venom delivery. Indeed, according to biophysicists in Germany and the US, many venomous reptiles do not inject their poison, as you might think. Instead, they rely on a toxic mix of surface tension and “tomato ketchup” physics. “Until we did, nobody had ever bothered about the question of why snake envenomation happens the way it does,” says team member Leo van Hemmen of the Technical University of Munich.

A few snakes do inject their venom, the rattlesnake being a well-known example. A rattlesnake’s fangs are like hypodermic needles, shooting venom into prey at high pressure from a poison gland in the snake’s head. But many venomous snakes and other reptiles do not have tubes in their fangs, and so cannot deliver pressurized venom. Often their fangs just have a single groove, running top to bottom.

Hydra-dynamics

Van Hemmen and his colleagues at Munich together with Bruce Young at the University of Massachusetts wanted to understand whether these grooves help in the venom delivery. To do so, the researchers milked some venom from a pair of snakes, then mixed it with equal parts of saliva, as would usually happen. Next, they measured the venom–saliva mixture’s viscosity for different values of shear rate – that is, the viscosity of the venom when it is between two surfaces that are moving relative to each other at a certain rate.

This process revealed an interesting fact about snake venom: it is a bit like tomato ketchup. Unlike water, which flows regardless of the forces acting on it, ketchup gets less viscous – or more able to flow – as the shear forces acting on it increase. This trait makes ketchup a “non-Newtonian” fluid.

Van Hemmen’s group believes snake venom’s non-Newtonian behaviour is integral to its delivery. When the venom is in the fang grooves, exposed only to air, the lack of shear forces means that it has a high viscosity. However, when the fangs penetrate skin, the shear forces increase, the viscosity decreases, and the venom can flow freely.

Surface tension draws venom

But there is more to a snake bite than non-Newtonian physics. Van Hemmen’s group also measured the venom mixture’s surface tension, a property that acts to minimize surface area and energy – by forming a fluid into droplets, for example. The researchers then used computer software to analyse how surface energy would be minimized in different groove shapes. In general, the researchers found that when the fangs are in air, surface tension keeps the venom in the groove. However, when the fangs penetrate flesh, the grooves and tissue form a tubular shape that increases surface area and minimizes surface energy, thereby drawing the venom in.

“I find this a very interesting study,” says Wolfgang Wüster of Bangor University in Wales, who is a biologist and expert on venomous snakes. “For many years, biologists have wondered about the function of the grooved rear fangs of many snakes. As a delivery system, it has often been dismissed as inefficient…This new study shows that a grooved fang is in fact an effective venom-delivery system that can introduce toxins into a bite wound fairly rapidly and effectively.”

However, Kenneth Kardong, a biologist who studies reptiles at Washington State University in Pullman, US, is not convinced that the grooves are there to deliver venom. He says the secretions of reptiles are a “cocktail of chemicals” with a variety of functions, including digestion. Although “the physics is interesting” , he says, the grooved fangs may only shift the fluid to the prey’s skin, and not further down, directly into the prey’s bloodstream where it would be most effective as a poison. “All roads may lead to Rome, but not all reptile secretions lead to venom,” he adds.

Even if grooved fangs are an efficient deliverer of venom, evolution suggests that they are probably not as effective as the rattlesnake’s tubular fangs. Hans Sues, a palaeontologist at the Smithsonian National Museum of Natural History in Washington, DC, has performed studies revealing that enclosed tubes developed from open-grooved fangs in reptiles during the Triassic period, more than 200 million years ago. “Such a transition had long been hypothesized as the tubular fangs in snakes develop by infolding during embryonic development,” he says. “Thus, despite the efficacy of open grooves, there was still development of fully enclosed canals.”

The research is published in Phys. Rev. Lett. 106 198103.

Has Fermi glimpsed dark matter?

New results from NASA’s Fermi Gamma-Ray Space Telescope appear to confirm a larger-than-expected rate of high-energy positrons reaching the Earth from outer space. This anomaly in the cosmic-ray flux was first observed by the Italian-led PAMELA spacecraft in 2008 and suggests the existence of annihilating dark-matter particles.

Physicists believe that about 80% of the mass in the universe is in the form of a mysterious substance known as dark matter. Unable to observe dark matter using light or other forms of electromagnetic radiation, researchers are attempting to find direct evidence of it on Earth using either heavily shielded underground detectors or with particle accelerators. But they also have a third, less direct, option – using satellites or balloon-based instruments to detect the particles that some theories predict are created in space when two dark-matter particles collide and annihilate.

The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) mission caused excitement in 2008 after it found significantly larger numbers of positrons (anti-electrons) at energies 10–100 GeV than expected. Taking into consideration only positrons produced when protons interact with the interstellar medium, physicists had calculated that at higher energies there should be a gradual drop in the number of positrons reaching the Earth. However, dark-matter collisions are expected to produce equal numbers of electrons and positrons over a given energy range. This would boost the ratio of positrons to electrons detected because positrons are substantially less abundant than electrons in the universe as a whole.

Positrons or protons?

The PAMELA results, however, were not watertight, mainly because of the possibility that the mission was confusing positrons with the far larger numbers of protons reaching its detectors. But the latest results from Fermi appear to remove these doubts. Although it is a gamma-ray telescope, Fermi in fact works by detecting electron–positron pairs and so is also well suited to studying cosmic rays. Unlike PAMELA it does not include a magnet to distinguish between electrons and positrons, but the Fermi scientists realized they could use the Earth’s magnetic field instead. This bends electrons and positrons in such a way that certain patches of the sky will contain just one kind of particle but not the other. So by totting up the signals coming from these regions, the researchers were able to separately measure the electron and positron fluxes, and hence work out the fraction caused solely by the latter.

The team observed a significant increase in the positron fraction at higher energies. This coincides with the PAMELA results, to within the errors on the Fermi measurements. The results of this analysis were presented at a conference in Rome last week by Fermi collaboration member Warit Mitthumsiri. Mitthumsiri’s colleague Stefan Funk of the SLAC National Accelerator Laboratory in California believes that the results constitute “a very nice confirmation” of the observations from three years ago, and maintains that the background noise has been properly accounted for. “There will be a small fraction of protons that will look like electrons,” he says, “but we are quite positive that we have subtracted that fraction correctly.”

PAMELA’s principal investigator, Piergiorgio Picozza of the University of Rome Tor Vergata, agrees. He says that, barring some unknown source of protons, the Fermi results “strongly support the positron excess at higher energy”, adding that the agreement is all the more compelling because the two data sets were derived using “different analysis, different detectors, and completely different experimental conditions”.

We can confirm the PAMELA result but it is still puzzling where these additional positrons come from Stefan Funk, SLAC

However, even if the results themselves are now on a firmer footing, their interpretation is still open to debate. In principle, the positron excess could point to a misunderstanding in how protons interact with the interstellar medium, but Funk believes that it is unlikely. What is more likely, he says, is the existence of some other, primary, source of positrons, but that could be either annihilating dark-matter particles or some more mundane astrophysical process, such as acceleration by pulsars. “We can confirm the PAMELA result,” he explains, “”but it is still puzzling where these additional positrons come from.”

AMS or Planck could provide answers

John Wefel, an experimental astrophysicist at Louisiana State University in the US, believes that the Alpha Magnetic Spectrometer (AMS) could help to establish what is causing the excess. The AMS has just become operational on the International Space Station and Wefel points out that it has a more powerful magnet than PAMELA and will therefore be able to probe positron fluxes at higher energies. “What AMS ‘sees’ may be very important in deciding between different models,” he says.

Neal Weiner of New York University believes instead that NASA’s Planck mission might provide the answer; he argues that if the positron excess really is due to dark-matter annihilation, then that annihilation should alter the cosmic microwave background. “Some people will jump and say this is clearly dark matter, and some will dismiss this as messy astrophysics,” he says. “But I think both reactions miss the point. This is science after all, so no-one’s gut feeling is really the question – we simply need more data, and we shall have more data.”

Quantum landscaping

USPS.jpg
Artist’s impression of a map of the Quantum Universe (Graphic courtesy of “ILC — form one visual communication”)

By Tushna Commissariat

Here’s a bit of Friday physics fun… I came across this rather interesting image that shows an artist’s impression of a map entitled “The Quantum Universe”. It includes six landmasses all floating in the Big Bang Ocean; including Dark Matter Landmass, Sypersymmetry Reef, Higgs Island and the Land of Ultimate Unification as well as others.

So go ahead and tell us which island you would like to settle down on. Be sure to look carefully at gems like Newton’s Lawn and Mount Einstein before you make your mind up!

To see a larger hi-res image follow this link.

Could Blackberry woes affect physics institute?

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Artist’s impression of the new Stephen Hawking Centre at the
Perimeter Institute, which will open in September. (Courtesy: PI)

By Hamish Johnston

Over the last decade the sleepy city of Waterloo, Ontario, has become a hotbed of theoretical physicists.

About 60 miles west of Toronto, the city is home to the Perimeter Institute for Theoretical Physics (PI). The PI counts Stephen Hawking as one of its visiting fellows and is also home to about 80 resident physicists – many of whom are household names in the physics community. The PI is also taking an innovative approach to training the next generation of theorists in its Perimeter Scholars International masters level course.

All of this is possible thanks to the generosity of Mike Lazaridus, who made his money by founding and running Research in Motion (RIM). The firm makes the Blackberry smartphone and its fortunes soared in the 2000s as the Blackberry became the must-have business tool.

Lazaridus has donated a whopping $170m to the PI, which he set up in 1999, and two other RIM executives have chipped in $40m more. Compare this to the $180m donated by the Canadian and Ontario governments and it is easy to conclude that the future success of PI and RIM will be linked.

That’s worrying because it seems that company’s heyday may be over, at least according to a market analyst writing in Canadian Business. Henry Blodget points out that the firm’s market share is dropping and tries to explain why.

While I don’t wish any ill on RIM, PI or Waterloo, I’m afraid that I agree with Blodget. Indeed, next to an iPhone a Blackberry looks like something, well, from the last decade. Let’s hope the same fate doesn’t befall the PI, which has done a fantastic job of boosting the profile of physics in both Canada and beyond.

Of course not everyone agrees with Blodget and Canadian Business has published an article taking the opposite viewpoint entitled Long live RIM.

Much ado about the LHC

USPS.jpg
Rolf-Dieter Heuer talking to journalists at the Royal Society, London.
(Courtesy: Tushna Commissariat)

By Tushna Commissariat

The Large Hadron Collider (LHC) at CERN has had its share of good and bad press over the past few years. Controversy and rumours abounded when the machine was switched on in September 2008. The mood then turned quickly to disappointment when its magnets failed and finally to euphoria when the first beams collided at 7 TeV in March 2010.

This week, a meeting to discuss the LHC and all things related was held at the Royal Society in London. The “Physics at the High Energy Frontier – the Large Hadron Collider Project” meeting took place on 16–17 May and saw leading lights of the project come together to discuss the collider and its future.

I was at the meeting for the second day, when a press briefing was held where CERN director Rolf-Dieter Heuer, plus Fabiola Gianotti and Guido Tonelli of the ATLAS and CMS experiments respectively, answered all of the questions that the Higgs-hungry reporters could throw at them!

The three speakers described how the collider has “surpassed all expectations” – experimental and computational. Talking about how the LHC is the very essence of global co-operation, Tonelli stressed that “no country could have done it as a stand-alone”. Heuer boasted that every year about 1000 students get their PhDs thanks to the LHC, while just the ATLAS experiment involves about 3000 researchers.

Explaining how things work at the LHC, Tonelli said, “We [experimental scientists] try to test the theory without prejudice. We ask our friends the theorists to come up with something that we can observe.” The collider has already produced the top quark in Europe for the first time and now it is poised to begin a regime of “new physics”, to look for supersymmetry (SUSY), multiple dimensions, matter–antimatter disparity and, of course, the Higgs boson.

The Higgs…or something else?

“We will have an answer to the Shakespeare question for the Higgs – ‘To be or not to be’ – by the end of 2012” declared a confident Heuer. While he did show a great deal of enthusiasm about discovering the Higgs, Heuer was also keen to point out that not finding the particle would be a great result in itself. “Not finding [the Higgs] when it does not exist is a success,” he exclaimed. “If it does not exist, we need to find something else that takes up the job of the Higgs and gives mass to elementary particles,” he added.

The LHC will run until the end of 2012 without any major breaks and Heuer is confident that it will decide the fate of the Higgs by the end of this run. “Physics will not be the same after 2012.” declared Tonelli. “It will change the view of the world.”

Not amused

One of the first questions, asked by BBC reporter Pallab Ghosh, was about the recent ”leak” of an unconfirmed sighting of the Higgs by ATLAS. A sighting that was later denied by a paper released by the ATLAS team and in interviews with physicists on various media channels.

“Unfortunately we live in a world of WikiLeaks, so it leaked!” said a grinning Gianotti. On a more serious note, she explained that such leaked results have not undergone the scientific scrutiny that is necessary, and hence are almost always insubstantial.

“The CERN management was not amused by the leak” said Heuer. He went on to ask journalists not to believe leaked results in the future. “Don’t trust it on first sight” he said. Although Heuer’s displeasure was clear, the leak did put the LHC back in the public eye after a few quiet months. Also, the media interest did provide the public with a rare insight into the vetting process that all scientific discoveries undergo. So perhaps the CERN management should lighten up and enjoy the renewed interest in the LHC!

USPS.jpg
Rolf-Dieter Heuer giving a talk about the future of the LHC at the Royal Society, London. (Courtesy: Tushna Commissariat)

Bumps and jumps

When asked about the Higgs-like ‘bumps’ seen at other experiments like the Tevatron and CERN’s Large Electron Positron Collider (LEP) the panel had mixed replies. The Tevatron bump was dismissed by Gianotti and Tonelli, as they both explained that it was too small, statistically speaking, and was only seen by one of the Tevatron’s two detectors. Would the LHC have a look for the Tevatron signal? “No”, was their reply.

However, “interesting events” seen at 115 GeV by the LEP just before its closure in 2000 are of interest to them. While Heuer did say that it is very difficult to determine if it was anything more than a “hint”, the LHC will be looking for the Higgs at that energy soon.

hawking.jpg

Colliding linearly

The International Liner Collider – a possible successor to the LHC – is another project that Heuer is excited about. He feels that CERN, with the LEP and now the LHC under its belt, would be the perfect host for the collider. “I think CERN has huge potential, not only on the human side, but on its experience side. We have all the instruments. So I see CERN in a very good position.” he said.

But what about the money? “If you have an excellent science case, you will get the money. Don’t ask for the money until you have the science figured out.” he said. He pointed out that, compared to the US, in Europe the politics of funding are more stable and for that reason CERN would be a better host.

Right: prototype microwave cavity for the ILC, illuminated for a “Science Night” in Hamburg. (Courtesy: DESY)

Art and science collide at CERN

In our latest video report, Ariane Koek, head of CERN’s arts programme, takes us beyond cutting-edge science to explore the thriving arts scene at what is Europe’s foremost particle-physics lab. “The scientists here are very creative, very engaged in things other than particle physics,” she tells physicsworld.com reporter James Dacey.

Koek’s job is to shape CERN’s arts policy and the lab is already building bridges with the art world by appointing artists as creative patrons. One of these is the celebrated British artist Antony Gormley, who recently donated a sculpture to CERN in recognition of the impact that particle physics has had on his work. Just press “Play” to get up close to Gormley’s work, which is currently hidden away in one of CERN’s warehouses.

This report is the final instalment of our four-part video series from CERN. Visit the physicsworld.com multimedia page for special reports from the ALICE and CLOUD experiments, as well as a short film about the search for the Higgs boson.

Researchers unveil the Einstein Telescope

Researchers have drawn up plans for the next-generation gravitational-wave observatory that will be 100 times more sensitive than current instruments. The Einstein Telescope, which is estimated to cost around €790m and be complete by 2025, will seek to directly detect gravitational waves and attempt to work out their origin and nature. It will differ from existing gravitational-wave detectors in being built underground.

Researchers will now begin carrying out a detailed technical design for the Einstein Telescope, which is expected to be complete by 2017, as well as selecting its location. The telescope is one of seven projects recommended by the Astroparticle European Research Area (ASPERA) network, funded by the European Commission, the CERN particle-physics lab and 17 countries including Germany, Russia and the UK.

Gravitational waves are ripples in the fabric of space–time that Einstein’s general theory of relativity predicts ought to pervade the universe. The Einstein Telescope – known as a third-generation gravitational-wave observatory – would be similar in design to existing labs such as the US-based LIGO gravitational-wave observatory in Hanford, Washington, and Livingston, Louisiana.

LIGO works by having two 4 km long interferometers at 90° to each other in which a laser beam is split and sent down each arm. The beams then bounce off test masses at the end of each arm and return to their starting point, where they interfere with one another. Any passing gravitational wave will make one arm slightly longer and the other slightly shorter, thereby changing the interference pattern in a measurable way.

Going underground

The Einstein Telescope will study the entire range of gravitational-wave frequencies – from 1 Hz to 10 kHz – from astronomical sources that can be measured on Earth. The observatory will be built underground at a depth of about 100–200 m and will consist of three underground detectors, each linked by two 10 km long interferometer arms.

One of the interferometers will detect low-frequency gravitational-wave signals from 2 to 40 Hz, while the other will detect the higher-frequency signals. “The fact that the Einstein Telescope will be underground allows us to extend the sensitive window down to lower frequencies, such as those below 10 Hz,” says Andreas Freise from the University of Birmingham in the UK, who leads the optical design of the telescope. “Many gravitational-wave signals from, for example, black holes crashing into each other, will have a significant signature in that range.”

LIGO is currently being upgraded to Advanced LIGO, which will make it 10 times more sensitive. According to Freise, physicists expect Advanced LIGO to make the first direct detection of gravitational waves, but as the Einstein Telescope will be a further 10 times more sensitive, it will be better placed to estimate the origins of gravitational waves and give information about the local gravitational environment around them.

Unbound planets could abound in the universe

Ten planets that appear to be drifting in interstellar space have been spotted by an international team of astronomers. The planets are so far from any host stars that they may not orbit a star at all, and could be drifting unbound through space. The team believes that such rogue planets could outnumber normal stars almost 2:1 and their existence could confirm computer simulations of solar-system formation.

More than 550 planets have so far been found beyond our solar system. The vast majority of these extrasolar planets – or exoplanets – have revealed themselves by their gravitational influence on their host star, or by the dip in brightness that they cause as they pass in front of their star. However, a clutch of 12 worlds had previously been found by gravitational micro-lensing.

This technique relies on the object of interest passing directly between the observer and a more distant background object. The mass of the foreground object acts like a lens and magnifies the light from the object beyond. If the foreground object is a star, then any orbiting planet leaves its own tell-tale fingerprint in the shape of the magnification. However, due to the need for an exact alignment, fewer than one in a million stars in the central part of the Milky Way are micro-lensed at any given time. This is why the number of exoplanets detected this way is low.

Sifting through 50 million stars

In an attempt to get around this problem the Microlensing Observations in Astrophysics (MOA) collaboration observes many stars at once. The new rogue planets were found in MOA observations of 50 million stars within the Milky Way between 2006 and 2007. “Over all the stars observed we are very confident that we witnessed 474 definite lensing events,” lead-author of the study Takahiro Sumi, of Osaka University, Japan, told physicsworld.com. Of these 474 events, 10 lasted for less than two days. Seven of these 10 events were later confirmed by data from the Optical Gravitational Lensing Experiment (OGLE) collaboration.

The more fleeting the duration of the event, the less massive the lensing object; a duration of less than two days implies the mass of the foreground object to be much less than that of a star. In fact, Sumi believes the culprits to be planets roughly the mass of Jupiter. What is more, no stars were observed within 10 astronomical units of the lensing objects – one astronomical unit is the distance between the Sun and the Earth and Saturn orbits at about 9 astronomical units. “There is a possibility that these planets do have a host star. However, direct imaging of exoplanets by other teams suggests that such distant planets are very rare,” Sumi explains. “This led us to conclude that the lensing objects are freely floating planets, unbound from any star,” he adds.

Because they are short-lived events, and the result of chance alignments, Sumi didn’t expect to uncover such a high yield of planet-lensing events with MOA. From statistical analysis of his data he was able to extrapolate a figure for how common these free-floating planets might be. “We found that unbound planets, with roughly the mass of Jupiter, should be 1.8 times more common than the stars we observed,” Sumi explains.

Scattered into space

The existence of rogue planets isn’t completely unexpected: they have been predicted from computer models of solar-system formation. “We think they are formed in the same way as other planets but get scattered from the system by gravitational interactions between them,” says Sumi. Joachim Wambsganss, of the University of Heidelberg, Germany, who was not involved in the work, says that this research quantifies this process for the first time. “We just didn’t know how often this happened,” he said. “This research gives us an idea,” he adds.

Wambsganss went on to describe the research as using a “clear and solid method”, however he thinks some people may not believe the claims of the rogue planets’ abundance. “They used a very extensive statistical analysis, using several different factors, but others may argue with the numbers they used,” he explains. One way of strengthening the research’s claims will be to use the next stage of data from the MOA experiments. “There are three more years of data for 2008–2010 that they can work through in the same way. They should find more of these events and this will provide an even stronger statistical basis for their claims,” he says.

The planets are described in Nature 473 349.

Mobile phones, but no jet packs

Have you ever wondered what happened to all the flying cars and personal ray guns we were promised? Anyone who has watched TV, gone to the cinema or read science fiction knows that by now we should inhabit a world full of amazing devices. And actually, we do: the problem is that when we look around, we see that the amazing devices we ended up with are mostly not the ones that science fiction predicted. So what happened? Why did we get mobile phones and the Internet instead of jet packs and teleporter systems?

James Kakalios’ book The Amazing Story of Quantum Mechanics starts out with various versions of this same question, and proceeds to make the case that quantum mechanics is responsible for most of the really cool devices we take for granted (and that a lack of breakthroughs in energy technology accounts for the missing jet packs and other gadgets). By exploring these unforeseen consequences of the quantum revolution, Kakalios sets out to accomplish two basic goals: explaining the theory of quantum mechanics to non-experts, and showing how this theory has given us cool stuff.

Given these goals, one thing that is particularly enjoyable about the book is that it is not yet another history of quantum mechanics. Explaining quantum mechanics for the non-specialist, without mathematics, is generally a daunting challenge, and a lot of writers seem to shy away from it by getting very philosophical or very historical very quickly. By basing his book on the science behind real devices, Kakalios is able to focus instead on the practical aspects of quantum theory.

Early in the book, Kakalios presents the reader with three “impossible ideas”. Briefly, they are: (1) light is composed of discrete packets; (2) matter exhibits wave properties; and (3) everything has intrinsic angular momentum. The expert will quickly recognize these ideas, and appreciate that they are not the standard starting point for presenting quantum mechanics in courses and textbooks. However, this is a good thing because these ideas have a closer connection with everyday experience and get directly to the issues relevant for technology. Too often, standard approaches focus initially on the wavefunction and its weirdness, but this does not readily lend itself to everyday analogies.

Another aspect of the book that makes it attractive to non-specialists is that essentially every quantum-mechanical idea is connected with a character or story from science fiction or superhero lore. Indeed, most chapters start with such stories, which provide unusual context for the topic at hand. For example, a section on wavefunctions begins with a story from the graphic novel Watchmen by Alan Moore, in which atomic physicist Jon Osterman is transformed into the superhero Dr Manhattan when experiments on the four fundamental forces of nature go spectacularly wrong. By asking why these experiments turned Osterman’s skin blue, or what it means for him to “gain control” over his quantum-mechanical wavefunction, Kakalios gets a unique starting point for addressing some rather abstract and challenging physics. And, of course, the real heroes of the development of quantum mechanics – the physicists and chemists who are in all the textbooks – also get their due.

Through this mixture of fiction and reality, the reader learns how the three impossible ideas of quantum mechanics were discovered, and what they really mean for the fundamental behaviour of matter. There is, however, one occasional drawback to starting each chapter with a fictional story.

For Kakalios, a physicist at the University of Minnesota who has previously written a book called The Physics of Superheroes, the distinction between science and science fiction is clear and obvious. However, readers who are less familiar with either the real history of science or the characters of science fiction may initially wonder whether the person being discussed is real or fictional. This is always made clear later in the chapter, but at first it can be disconcerting.

Another weakness of the book is that although Kakalios does a great job of handling the “impossible” ideas of quantum mechanics, he does seem to assume that the reader is already familiar with energy in the same way physicists are. Admittedly, the ideas of energy conservation are addressed to some degree, but a non-specialist could run into difficulties when their everyday views of energy fall short of the physics view of energy. In my experience of teaching physics to non-specialists, this difference between the common usages of the word “energy” and the specific physics concept is one of the biggest challenges students face. In everyday usage, energy is often viewed as an independent thing, such as an “energy field” or an “energy beam”. In physics (and in the applications in this book), energy is a property of things and it can come in many forms.

As we journey with Kakalios through the three impossible ideas of quantum mechanics, he provides the reader with a number of powerful analogies. Perhaps the most important analogy in the later chapters concerns the electron band structure in solids, which comes up because the devices that interest Kakalios are all grounded in solid-state physics. Explaining how they work therefore requires him to address the electronic behaviour of materials. To do this, he suggests we imagine the electrons in a theatre, complete with orchestra, balcony and mezzanine seating. As we explore the impact of filling or not filling the orchestra, and jumping between the different seating options, we learn how materials gain their all-important electronic properties and what this means for technology. The use of the theatre analogy is perhaps the strongest element in the book. Having used it to build a mental picture of the world of electrons, Amazing Story concludes with explanations of the inner workings of many modern devices, from transistors to LEDs and MRI.

Overall, the book accomplishes its goals. By focusing on concrete applications, real-world devices and the sometimes fantastical vision of science fiction, the abstract world of quantum mechanics is made accessible to the non-specialist. As a bonus, we learn how quantum mechanics actually did make possible some of the powers and devices envisioned in early- to mid-20th century science fiction – and, even more importantly, how it gave us a whole host of unforeseen wonders.

Between the lines: multiverse special

Multiverses on parade

A universe with infinite spatial extent will contain infinitely many mini-universes. An infinite number of these mini-universes will be exactly like our own. Welcome to the mind-blowing nature of infinity – and the sometimes equally mind-blowing nature of the multiverse, which is a common theme among the books in this month’s column. First up is Brian Greene’s The Hidden Reality, which explores nine variations on the multiverse theme. Of these, the type of multiverse that arises as a consequence of infinite space – Greene calls it the “quilted multiverse” because regions of space will repeat like patterns in a quilt – is actually one of the easiest to comprehend. From then on, things get both more complicated and more interesting, as Greene leads the reader through cosmic inflation, string theory and the “many worlds” interpretation of quantum mechanics. Greene’s tour of multiverses also takes in some even more exotic territory, as he considers the possibility that our distant descendents could one day create simulated universes – or that we are living in one such simulation (as in the film The Matrix). All of this is, of course, extremely speculative, and large swathes of it seem fated to remain that way forever. Yet those who believe – not unreasonably – that multiverse theories have more in common with religion or philosophy than they do with science should still give Greene’s book a chance. The chapter on “Science and the multiverse”, in particular, explores the many criticisms of multiverse theories in a sensitive and thoughtful way. Sceptical readers will find they can appreciate Greene’s logic and candour, even if they ultimately decide to disagree with him.

  • 2011 Allen Lane/Knopf £25.00/$29.95hb 384pp

Click here for physicsworld.com‘s interview with Brian Greene

Many universes, many quotations

In contrast to Greene’s book, which focuses on the most up-to-date views on multiverse theories, John Barrow’s The Book of Universes takes a more historical approach. By beginning with the universe according to Aristotle and other Greek philosophers, and continuing through Copernicus, Kant and Laplace into the modern era, Barrow makes an important point: our concept of the universe has expanded tremendously over the years, so it is unsurprising that scientists are now seeking to extend it still further. The downside of this leisurely tour, however, is that the book takes an awfully long time to get going. After 100 pages, we have only just reached Einstein and the 20th century. The pace does pick up later in the book, with a good chapter on “post-modern universes” that covers, among other things, Barrow’s own research on the possibility that the speed of light was not constant in the early universe. However, even here the narrative is repeatedly interrupted, because either the author or his publisher thought it was a good idea to chuck in at least one quotation every six paragraphs or so. We do not normally discourage witty comments from scientists, but The Book of Universes contains so many that they actually get in the way. Worse, for every quote that reveals a deeper truth – such as Chaim Weizmann’s comment that “Einstein explained his theory to me every day and on my arrival I was fully convinced that he understood it” – there seem to be at least two that have made it into the book simply because they are vaguely amusing. Whoever was responsible for filling the book with them should have heeded the words of crime novelist Dorothy L Sayers, who once wrote that “A facility for quotation covers the absence of original thought.”

  • 2011 Bodley Head £20.00 368pp

A sceptical overview

A little over a century ago, some British mathematicians and physicists thought they had uncovered the theory of everything. According to their theory, the fundamental particles of nature were actually composed of different types of vortices, swirling in a perfect, frictionless fluid. This theory was beautiful, elegant and coherent. As late as 1903, the American physicist Albert Michelson declared that it “ought to be true, even if it is not”. Vortex theory could also explain – in a way that traditional theories of solid atoms could not – the existence of lines in the spectra of chemical elements: clearly, the lines represented different modes of vibration in the vortex atom. Of course, no-one now believes in vortex atoms, but as Helge Kragh explains in Higher Speculations: Grand Theories and Failed Revolutions in Physics and Cosmology, the rise and fall of vortex theory makes a useful cautionary tale for modern theory-of-everything enthusiasts. Kragh, a historian of science, is interested in how such explanations arose, why they failed and whether any parallels can be drawn with modern theories – including those that incorporate some version of a multiverse. Much of the book’s second half is devoted to teasing out the links between theories of the multiverse, string theory and the anthropic principle; Kragh defines the latter as “an attempt to deduce non-trivial consequences about nature from the consideration that what we observe must be compatible with our existence”. These three concepts have quite separate historical origins, Kragh observes, yet since the mid-1980s some elements of them have merged. His scholarly book offers a sceptical but largely impartial overview of the multiverse and related speculation.

  • 2011 Oxford University Press £35.00/$63.00hb 408pp
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