Move over Milky Way, elliptical galaxies are the most habitable in the cosmos

Elliptical galaxy SDSS J162702.56+432833.9 could be full of life. NASA/ESA/wikimedia, CC BY-ND

The search for extraterrestrial life is surely one of the most important tasks we humans can undertake. However, the cosmos is vast and we don’t really have any idea which bits of it are actually habitable. But what if we could target the search? We have built the first-ever “cosmobiological” model mapping the galaxies in our local universe to help us understand which ones are habitable. Surprisingly, we found that our own galaxy was not one of the top candidates.

Ingredients for habitability

Drawing on our understanding of habitable zones within a galaxy, we proposed that the overall habitability of any galaxy depends on three key astrophysical criteria. One is simply the total number of stars capable of hosting planets, which is roughly related to the size of the galaxy. Another is the total amount of the building blocks of planets and life – such as carbon, oxygen and iron – the so-called astrophysical “metals”. Another is the negative influence of supernova explosions, whose powerful (and poisonous) radiation could potentially inhibit the formation and evolution of complex life on nearby planets.

Milky Way: not so special anymore. ESO/wikimedia, CC BY-SA

Interestingly, the largest survey of its kind ever undertaken, data from the Sloan Digital Sky Survey observes exactly these three key properties for more than 150,000 galaxies in the nearby universe. This data shows that the largest galaxies have the largest amount of metals. Sifting through this data set we found that giant elliptical galaxies, which have a rounded shape rather than spiral arms like our Milky Way, win the “most-likely-to-be-habitable” title. Indeed, each giant elliptical that is at least twice as big as the Milky Way and has a tenth of its supernova rate could potentially host 10,000 times as many habitable (Earth-like) planets.

Our results, recently published in the Astrophysical Journal Letters, also show that they typically have a low rate of supernova explosions, ensuring that most of these planets remain unmolested by harmful radiation.

This is the first computation that discusses life on cosmological scales, rather than just within individual galaxies like the Milky Way. The model therefore opens up a new avenue, extending the understanding of habitability around individual stars to a true “cosmobiological” context, which allows us to discuss the habitability of the entire universe.

One of the most attractive features of the model is that that data used includes the entire history of all the galaxies in the universe that we see around us. The relationship between the number of stars, amount of metals and rate of supernova explosions essentially acts as the “fingerprint”, uniquely identifying how any given galaxy formed. This is a key bit of information that we need to understand the chances of galactic habitability and which has been missing in this field.

Are we in the wrong galaxy?

By all accounts, our Milky Way is a typical spiral galaxy of average size that roughly makes one star like our sun every year. Given that ellipticals are much more hospitable to habitable planets raises the interesting question of whether life here in the Milky Way is just a freak of nature.

Or does the presence of life on at least one planet in the Milky Way imply that these big elliptical galaxies might be absolutely teeming with life?

One drawback is that the nearest elliptical galaxy to the Milky Way, called Maffei1, is so far away that any radio signals beamed from this cosmic neighbour would take 9m years to reach us. Surveys such as the SETI (Search for Extraterrestrial Intelligence) that continually maps the skies for anomalous signals might one day detect such a signal in the far future, a call to us from our (not so) nearest neighbours.

Firms that exploit the dark side of technology will find it leads to losses as well as gains

All smiles? Not so much. Jakub Kaczmarczyk/EPA

Has technology enabled us, or enslaved us? This is a question posed by recent coverage of the apparently unsettling working practices and work culture at Amazon, among others. The employee monitoring, long hours and continuous performance measurement reported in the New York Times wouldn’t be possible without modern information technology. It seems for some the world of office work has become, as the article states: “more nimble and more productive, but harsher and less forgiving”.

The irony is that the very qualities of modern technologies that we find helpful and increasingly cannot do without – constant availability, reliability, mobility, speed and user-friendliness – also cause a number of negative effects. We like that technology-enabled flexibility allows us to work from home when our child is sick, but the same flexibility and reach make us contactable at all hours on all days, and may turn us into email addicts if we are not careful.

The near-infinite options and capacity for customisation offered by today’s app-driven devices leads us to tinker, experiment and discover ways to use them that may not be good for us – individually, or collectively.

It giveth, and it taketh away

One of the examples given for the Amazon work experience was of emails arriving past midnight, with subsequent emails asking why they were not answered. Recent research shows technology causes “technostress”, which reveals itself in a number of ways.

Because information comes at us so from so many sources, we feel forced to work faster to process it all, and take on more than we can handle. Because our colleagues might respond immediately, we feel the pressure to adapt and increase our pace. Keep this pressure up 24/7 and we find ourselves working during holidays, during family time and social engagements, and our lives are invaded by the same technology we value.

Maybe the Luddites had a point after all. Unknown

Worse is the more recent experience of “FOMO” – the fear of missing out – where we feel anxious and insecure that if we’re not sufficiently connected and up-to-date then others may get ahead, or that socially we may miss out.

Employers can play upon such fears. For example, Amazon’s internal phonebook instructs colleagues on how to send anonymous feedback on colleagues, such as perceived “inflexibility” or “complaining about minor tasks”. When enough staff experience these effects and feel that work tasks should be immediately attended to just because they’re available through a smartphone, an institutionalised work culture develops where technostress is the norm rather than something to be avoided. It’s worth noting here that research links technostress with reduced satisfaction, productivity and innovation – and so offsets many of technology’s purported benefits.

Technology is what we make of it

So what do organisations do about this dark side to the technology with which they equip their staff? They can use it to serve a command and control work culture if that what they want to create. Such technocratic cultures are easily brought about today, and far more powerful and insidious than Jeremy Bentham’s Panopticon.

Or companies can go to the other extreme, such as preventing access to email servers outside working hours which robs the firm and their employees to some extent of the benefits of technology altogether. Neither is entirely desirable.

However, we’re beginning to see some examples of thoughtfulness and deliberation in the way organisations deal with technostress. For instance, in the UK Vodafone provides awareness programs to employees on the potential dangers of not knowing when to shut off from work while working from home.

Or, research which shows that our interaction with technology depends very much on the individual and their situation, which indicates a need to take into account the varying nature of organisations and staff when trying to set out policies that could help change the way we use technology for the better. In any case, at a very minimum an awareness of this dark side is an important first step.

From steam engines to railroads and to factories of mass production, technology has been the primary structuring force in our economic enterprise. The tussle between whether technology works for us or the other way around is not new; what we are seeing today is this tussle played out at scale and speed. What we need to ensure is that it is we who use our technology, rather than allowing it to use us.

Why we think the weather affects how a cricket ball swings ... when it doesn't

Swing and a miss. Anthony Devlin/PA

Following the rollercoaster 2015 Ashes series, which saw England defeat Australia 3-2, the two teams are set to meet again in a series of one-day games – weather permitting, that is. It’s been a cloudy and humid summer in much of the UK, and if you believe folklore, that might have been affecting the games.

In the last Test Match at the Oval, England captain Alastair Cook, unusually for that ground, elected to field first after winning the toss. The Australians subsequently went on to amass nearly 500 runs in their first innings and England lost the game. That no commentator questioned the wisdom of Cook’s decision, despite it backfiring in spectacular fashion, is because so many believe that cloudy, humid weather conditions favour swing bowling (where the ball curves in the air after being released by the bowler and before it hits the ground).

At the beginning of the Oval Test Match, television and press pundits were talking about the conditions favouring the bowlers. Cook himself explicitly mentioned the overcast conditions as being a factor in his decision to bowl first in an interview with Channel 5.

The power of the weather

Where does this almost unanimous belief in the power of the weather come from? In part, it comes from potent legends such as that of Australian bowler Bob Massie, who famously took 16 wickets on his Test Match debut at Lords on a day where conditions have been described as “Perfect … humid, the air was heavy and the clouds were oyster in hue.” But is there any systematic evidence for the phenomenon beyond this type of compelling anecdote?

It turns out that there is actually rather a lot of scientific evidence that draws on aerodynamic experiments, often using wind tunnels with variable atmospheric conditions. The result? None of it finds support for the idea that humid overcast conditions affect how much the ball swings.

The first scientific study of cricket ball swing was published as long ago as 1955 and a growing body of research has periodically been reported in mainstream media outlets. There is no reason to think that an increasingly data-driven, professional cricket community is unaware of the evidence. So what accounts for the limpet-like stickiness of this roundly debunked theory?

Perceptions are not what they seem

Part of the reason might simply be lack of information, understanding or the possession of outright misinformation. The idea that humid air is thicker than dry air seems to provide a plausible common-sense explanation for the swing effect. In fact – and counter-intuitively – humid air is less dense than dry air.

A growing body of evidence on “motivated cognition” explains why even when faced with clear scientific evidence, people may not alter their opinions to match the information. Motivated cognition essentially suggests that individuals unconsciously process information in order to derive conclusions that suit their goals or preferences.

Research on motivated cognition has shown how people with different ideologies do not come to the same conclusions on controversial scientific issues such as global warming or vaccination, given the same information. In my own work, I have shown this to be the case for attitudes to prenatal genetic testing.

On the ropes. From www.shutterstock.com

Why would people want to believe that cloudy days are better for swing bowling? Simply, this is the accepted view of the entire cricket community. To believe otherwise would be to lose credibility with one’s in-group.

Imagine the reaction if Alastair Cook had batted first at the Oval on a cloudy, humid day and England had gone on to lose the match. Motivated cognition would suggest that in such cases where the predicted conditions are not accompanied by curving deliveries, cognitive work in the form of ad hoc explanations will be carried out to preserve the initial belief. Hence we saw commentators during the final Ashes test match suggesting that the bowlers didn’t get it quite right on the first morning or that the Australians batted well enough to neutralise the swing.

Paradoxically, the more expert knowledge of cricket someone has, the more these ad hoc rationalisations will convince both themselves and others, based on their deep knowledge of other aspects of the game.

Alternative explanations

Psychological research on the persistence of misinformation suggests that false beliefs are difficult to correct without a plausible causal account to replace the erroneous one. There is little if anything written or discussed in this regard in the media that could capture the imagination of those currently in thrall to the accepted narrative. In reality, there are several hypotheses that appear eminently plausible and that could be advanced as alternative explanations.

The most obvious of these is that if a bowler believes that overcast conditions are conducive to swing, then they will make sure to bowl so as to impart maximum swing when those conditions prevail. In fact this is exactly what Bob Massie said in a radio interview after his spectacular 1972 performance at Lords:

Once I woke up and looked out of the window and saw the greyness there, I knew it was going to be a day that if I, you know, bowled fairly well, I should get wickets because it was one of those tailor-made days for swing bowling.

Another possibility is that, believing that the conditions will favour swing bowling, swing bowlers in the squad are more likely to be picked in the final team by selectors on the morning of a match and then captains will deploy this type of bowler more often during the period of play when conditions appear to be favourable.

Is there even anything to explain?

Full swing. PitchVision, CC BY-ND

But isn’t this all jumping a little ahead? What systematic evidence do we have that shows that there is more swing on display under these conditions (irrespective of why it may be)? To the best of this writer’s knowledge, there is none. There are only the powerful anecdotes previously mentioned and the firm conviction from those who play and watch the game that the phenomenon is real. Is it therefore possible that there really isn’t any observable connection between weather and swing but that psychological illusions are at play?

Nobel prize-winning psychologist Daniel Kahneman and his colleague Amos Tversky showed that the way people think about probability and come to judgements based on evidence is subject to biases that make us rather poor intuitive scientists. Examples such as Massie’s test match are vivid and memorable.

Confirmation bias means that we seek out, or retrieve from memory, examples of events that are consistent with our prior beliefs and ignore information that is inconsistent. These two well-documented cognitive biases mean that we are far more likely to recall the instances when the ball swung strongly under cloudy skies than when it behaved in the same way under the blazing sun. To see an illustration, click here.

How to win more often

What should we conclude from all this? If I were England’s Director of Cricket, Andrew Strauss, I would want to know at minimum whether there is any truth to the basic contention that weather affects swing, in order to maximise the advantage gained from the England captain winning the toss.

The English Cricket Board has access to the necessary data from TV and the Hawkeye technology to work this out. If data and science can make the next series an even greater triumph for England than the last, why not embrace it?

Six amazing sights that look even better from the International Space Station

Hurricane Arthur photographed by ESA astronaut Alexander Gerst. ESA/NASA

Imagine seeing the lights of cities spreading around the Nile Delta and then in less than an hour gazing down on Mount Everest. The astronauts on the International Space Station (ISS) are among the lucky few who will have this humbling, once-in-a-lifetime experience of seeing the beauty of Earth from space.

The ISS doesn’t just offer spectacular and countless views of the natural and man-made landscapes of our planet. It also immerses its residents into the Earth’s space environment and reveals how dynamic its atmosphere is, from its lower layers to its protective magnetic shield, constantly swept by the solar wind.

The best views are seen from the Cupola, an observation deck module attached to the ISS in 2010 and comprising seven windows. So, what are the amazing sights that you can see from the space station?

1. Storms and lightning

When the ISS orbits over a sea of thunderclouds, it’s not rare for astronauts to witness an impressive amount of lightning. What is unusual, however, is seeing lightning sprites, which were observed on August 10th by astronauts aboard the space station.

ISS astronauts spotted a sprite (the red jellyfish-like structure on the right of the image) appearing above thunder clouds on August 10, 2015 NASA

Sprites are electrical discharges, similar to thunder lights. However, instead of occurring in the lower layer of Earth’s atmosphere, these very fast, red-coloured discharges (due to the excited nitrogen at this altitude) occur much higher up and are as such difficult to observe from the ground.

2. Sunrises and sunsets

Sunset over the Indian Ocean. NASA/ESA/G Bacon

With the ISS orbiting the Earth every 90 minutes, astronauts can see the Sun rise and set around 16 times every 24 hours. The dramatic views from the station display a rainbow-like horizon as the Sun appears and disappears beyond the horizon.

Swiftly flow the days

The changes in colour are due to the angle of the solar rays and their scattering in the Earth’s atmosphere. If similar jaw-dropping views can be seen from Earth, seeing our mother planet lit up in the rising Sun certainly adds to the intensity of the picture.

3. Stars and the Milky Way

Amazing sightings of distant astronomical objects as seen from the space shuttle

From the ground, atmospheric conditions and light pollution affect our ability to see stars and other celestial bodies. As light travels through layers of hot and cold air, the bending of its rays render a flickering image of these distant objects, while atmospheric particles such as dust prevent from seeing fainter objects such as nebulae and galaxies. The lack of an atmosphere at the orbiting altitude of the ISS allows the residents on the space station to see the stars, the Milky Way and other astronomical features with much greater clarity than is possible on Earth.

4. Meteor showers

The disintegration of a Perseid meteor photographed in August 2011 from the ISS. NASA

Astronauts aboard the ISS can also witness the disintegration of meteoroids in the Earth’s atmosphere. Those small bodies are fragments detached from celestial bodies such as asteroids and comets. As they enter in the Earth’s atmosphere at great speed, the heat due to the body interaction with air rapidly destroys them. Whereas the chance of seeing them from the ground is very much weather dependent, being on the ISS guarantees the best seats to watch these shooting stars flaming across our planet’s sky.

5. Auroras

Also known as northern and southern lights, auroras are created when solar storms, consisting of large magnetised clouds of energetic particles launched from the sun, or strong solar wind, interact with the Earth’s magnetic shield. Upon collision with the Earth, these solar streams energise particles within the planet’s magnetic shield.

Time lapses showing the ISS travelling through auroras

When they enter the upper layer of the Earth’s atmosphere, these energetic particles excite nitrogen and oxygen atoms present at these altitudes. Then when they return from their excited state, these atoms emit light of different colours indicative of the amount of energy they absorbed. This typically produces green and red, ribbon-like curtains.

6. Cosmic rays

Galactic cosmic rays aren’t really a phenomenon you can see. These energetic sub-atomic particles come from intense astronomical sources such as exploding stars or black holes. If they pass into the body they can damage tissue and break DNA, causing various diseases over the course of time.

Most cosmic rays do not penetrate in the thick atmosphere of the Earth. Since the ISS sits outside this protected zone, its astronauts are much more likely to be struck by the particles. Astronauts regularly see flashes of light when they close their eyes, which is thought to be caused by cosmic rays interacting with body parts that play role in vision, such as the optic nerve or visual centres in the brain.

Solar storms, which have a strong magnetic structure, act as a shield against cosmic rays. A solar storm passing by the Earth can be indirectly witnessed by astronauts aboard the ISS via a drop in the count of cosmic rays, also known as the “Forbush decrease”. What a sensation it must be to “feel” a storm passing by the Earth’s system.

Overthinking could be driving creativity in people with neurotic disorders

Constantly lost in thought? You may want to make the most of it. Radharani, Shutterstock

People who suffer from neuroticism – a condition characterised by anxiety, fear and negative thoughts – are extremely tuned in to looking for threats. For that reason, you may expect them to perform well in jobs requiring vigilance: stunt pilots, aviators and bomb defusement. Yet, the evidence suggests they are actually more suited to creative jobs.

Exactly what drives neuroticism and the creativity it is associated with is not known. But researchers have now come up with a theory which suggests that it could be down to the fact that people who score highly on neuroticism tests, meaning they are prone to anxiety or depression, tend to do a lot of thinking – often at the expense of concentrating at the task at hand.

Past, present and future

The hypothesis, which is yet to be experimentally verified, is an extension of what we already know. People who have neurotic traits typically look for things to worry about (a mechanism dubbed “self-generated thinking”). For example, people who get depressed are consumed by such self-generated negative thoughts that they forget what they are supposed to be doing. In other words, they are not very tuned in to the ”here and now”, which is pretty important if you need somebody to concentrate on defusing a bomb.

What the new research helps to do is explain the underlying brain mechanisms that interfere with “on the job thinking”. A certain amount of brain arousal is great for concentration but too much interferes with clear thinking and that’s what you want when performing stunts, flying planes, and disposing of bombs. Isaac Newton is sometimes described as a neurotic. Bonhams, wikimedia

So where does the creativity come in? The authors argue that people who engage in self-generated thinking are creative because they are not rooted in reality – they are away with the fairies. Indeed, they may resist attempts to get them to concentrate on reality whilst they focus on their own thoughts. It is hardly a surprise, then, that their ideas can be new, whacky and original.

So while people scoring high on neuroticism may struggle with a lot of stress, they can still have a successful working life. They may actually be able to find creative solutions to problems that didn’t exist in the first place, and in the process come with some pretty useful and imaginative stuff. Rather like Billy Liar, in his escape from his tedious existence conjuring up some fairly exciting daydreams.

Remaining questions

We know that people who are clinically depressed spend an extraordinary amount of time living in the past. We know that people diagnosed with chronic worry (Generalised Anxiety Disorder) spend an extraordinary amount of time living in the future. The strength of the study is that it pulls together what is already known about people who spend a lot of time engaged in distorted thinking, some of which can be labelled as creative.

The authors argue that this creative flair applies specifically to problem solving, as they believe rumination and worry improve such skills. However, this is questionable as there is actually evidence that people who are depressed or worry are not very good at problem solving at all. Indeed, one of the interventions recommended for both conditions is Problem Solving Therapy. To adequately solve problems you need to be approaching reality and its problems, not avoiding them through aimless thinking. The new study falls short by not discussing this.

Anxiety and depression can be a lonely place. hikrcn

The authors also argue that psychological interventions such as meditation and mindfulness – which are thought to dampen some of these heightened responses by grounding people in the “here and now” – may do more harm than good. The jury is still out, but there is enough evidence available suggesting the benefits of mindfulness for people who are depressed and anxious with limited side effects.

Neuroticism, by its very nature, alerts you to past and future danger and some individuals can make good use of that. And that can be good. Our caveman ancestors came equipped with primitive brain parts allowing them to engage in predicting threat. But even if anxious or depressed people are able to come up with some great ideas, they are surely far more likely to contribute to society in the long run if they can find relief from their suffering.

With silicon pushed to its limits, what will power the next electronics revolution?

rbulmahn, CC BY

The semiconducting silicon chip launched the revolution of electronics and computerisation that has made life in the opening years of the 21st century scarcely recognisable from the start of the last. Silicon integrated circuits (IC) underpin practically everything we take for granted now in our interconnected, digital world: controlling the systems we use and allowing us to access and share information at will.

The rate of progress since the first silicon transistor in 1947 has been enormous, with the number of transistors on a single chip growing from a few thousand in the earliest integrated circuits to more than two billion today. Moore’s law – that transistor density will double every decade – still holds true 50 years after it was proposed.

Moore’s law still holds true after 50 years. shigeru23, CC BY-SA

Nevertheless, silicon electronics faces a challenge: the latest circuits measure just 7nm wide – between a red blood cell (7,500nm) and a single strand of DNA (2.5nm). The size of individual silicon atoms (around 0.2nm) would be a hard physical limit (with circuits one atom wide), but its behaviour becomes unstable and difficult to control before then.

Without the ability to shrink ICs further silicon cannot continue producing the gains it has so far. Meeting this challenge may require rethinking how we manufacture devices, or even whether we need an alternative to silicon itself.

Speed, heat, and light

To understand the challenge, we must look at why silicon became the material of choice for electronics. While it has many points in its favour – abundant, relatively easy to process, has good physical properties and possesses a stable native oxide (SiO₂) which happens to be a good insulator – it also has several drawbacks.

For example, a great advantage of combining more and more transistors into a single chip is that it enables an IC to process information faster. But this speed boost depends critically on how easily electrons are able to move within the semiconductor material. This is known as electron mobility, and while electrons in silicon are quite mobile, they are much more so in other semiconductor materials such as gallium arsenide, indium arsenide, and indium antimonide.

The useful conductive properties of semiconductors don’t just concern the movement of electrons, however, but also the movement of what are called electron holes – the gaps left behind in the lattice of electrons circling around the nucleus after electrons have been pushed out.

Modern ICs use a technique called complementary metal-oxide semiconductor (CMOS) which uses a pair of transistors, one using electrons and the other electron holes. But electron hole mobility in silicon is very poor, and this is a barrier to higher performance – so much so that for several years manufacturers have had to boost it by including germanium with the silicon.

Silicon’s second problem is that performance degrades badly at high temperatures. Modern ICs with billions of transistors generate considerable heat, which is why a lot of effort goes into cooling them – think of the fans and heatsinks strapped to a typical desktop computer processor. Alternative semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) cope much better at higher temperatures, which means they can be run faster and have begun to replace silicon in critical high-power applications such as amplifiers.

Lastly, silicon is very poor at transmitting light. While lasers, LEDs and other photonic devices are commonplace today, they use alternative semiconductor compounds to silicon. As a result two distinct industries have evolved, silicon for electronics and compound semiconductors for photonics. This situation has existed for years, but now there is a big push to combine electronics and photonics on a single chip. For the manufacturers, that’s quite a problem.

Semiconductor lasers, where alternatives to silicon such as germanium have already found a role. 彭家杰, CC BY-SA

New materials for future

Of the many materials under investigation as partners for silicon to improve its electronic performance, perhaps three have promise in the short term.

The first concerns silicon’s poor electron hole mobility. A small amount of germanium is already added to improve this, but using large amounts or even a move to all-germanium transistors would be better still. Germanium was the first material used for semiconductor devices, so really this is a “back to the future” move. But re-aligning the established industry around germanium would be quite a problem for manufacturers.

The second concerns metal oxides. Silicon dioxide was used within transistors for many years, but with miniaturisation the layer of silicon dioxide has shrunk to be so thin that it has begun to lose its insulating properties, leading to unreliable transistors. Despite a move to using rare-earth hafnium dioxide (HfO₂) as a replacement insulator, the search is on for alternatives with even better insulating properties.

Most interesting, perhaps, is the use of so-called III-V compound semiconductors, particularly those containing indium such as indium arsenide and indium antimonide. These semiconductors have electron mobility up to 50 times higher than silicon. When combined with germanium-rich transistors, this approach could provide a major speed increase.

Yet all is not as simple as it seems. Silicon, germanium, oxides and the III-V materials are crystalline structures that depend on the integrity of the crystal for their properties. We cannot simply throw them together with silicon and get the best of both. Dealing with this problem, crystal lattice mismatch, is the major ongoing technological challenge.

Different flavours of silicon

Despite its limitations, silicon electronics has proved adaptable, able to be fashioned into reliable, mass market devices available at minimal cost. So despite headlines about the “end of silicon” or the spectacular (and sometimes rather unrealistic) promise of alternative materials, silicon is still king and, backed by a huge and extremely well-developed global industry, will not be deposed in our lifetime.

Instead progress in electronics will come from improving silicon by integrating other materials. Companies like IBM and Intel and university labs worldwide have poured time and effort into this challenge, and the results are promising: a hybrid approach that blends III-V materials, silicon and germanium could reach the market within a few years. Compound semiconductors have already found important uses in lasers, LED lighting/displays and solar panels where silicon simply cannot compete. More advanced compounds will be needed as electronic devices become progressively smaller and lower powered and also for high-power electronics where their characteristics are a significant improvement upon silicon’s capabilities.

The future of electronics is bright, and it’s still going to be largely based on silicon – but now that silicon comes in many different flavours.

Solved: the mystery of why it's impossible to pull apart interleaved phone books

No glue, only friction. Danny Nicholson/Flickr, CC BY-NC-ND

People, trucks and even military tanks have tried and failed the task of pulling apart two phone books lying face up with their pages interleaved, like a shuffled deck of cards. While physicists have long known that this must be due to enormous frictional forces, exactly how these forces are generated has been an enigma – until now.

A team of physicists from France and Canada has discovered that it is the layout of the books coupled with the act of pulling that is producing the force.

The power of approximation

Finding an approximate solution to a complex problem is an essential skill in science (and in life). Often we are faced with questions that we can’t answer exactly, but sometimes good enough is, well, good enough. Enrico Fermi, one of the greatest physicists in the 20th century, has given his name to such “Fermi Questions” – as he was famous for encouraging this skill in his students.

Here’s one example: “How many piano tuners are there in Chicago?”. I have no idea, and I’m not sure Fermi knew either. But by estimating the population of Chicago, the fraction that might play the piano, and how often a piano needs tuning, you can come up with a pretty good guess, without diving into the phone book (it’s probably closer to 100 than to 1,000).

Doing these “back-of-an-envelope” calculations is usually the first step in approaching a scientific question. Sometimes that is as far as you need to go. Sometimes it tells us that the question is worth investigating more to find the exact answer.

Not even Brian Blessed can do it.

This is exactly what the team investigating the friction of phone books did. The back-of-the-envelope answer is friction between the pages. However, assuming the friction is proportional to the number of pages drastically underestimates the total force that is generated (which seems to rise exponentially with the number of pages). But previous attempts to improve this simple model – by including the effects of gravity and air pressure pushing the pages of the books together – have all failed to explain the result.

Surprisingly simple

So, when the back-of-the-envelope calculation fails, things get serious. In this case, the traction instrument was brought out (think the opposite of a vice), it was used to pull books apart while measuring the force required to do so. But not just any books. Rigorously prepared test books with specific numbers of pages, built from paper sheets of exact dimensions, interleaved to high precision.

Data in hand, a mathematical model was put together, and it turned out to be driven by a surprisingly simple fact. The pages of each book are separated by the interleaving and end up “spreading out”, lying at a slight angle from the spine. When the books are pulled away from each other, the pages want to move back closer together and end up squeezing the interleaved pages from the other book. And gripping something tightly greatly increases the friction.

Just impossible.

As an example, imagine a person with long hair in a swimming pool. While floating underwater, their hair can spread out – much like the pages of the books are spread out by the interleaving. Then, if our volunteer swims off, their hair will naturally move close together, following their head which is pulling it along. The pages of our books also want to move close together behind the thing pulling them (the spine of the book), but instead just squeeze more tightly on the pages of the other book, which are in the way. Pulling harder on the books only increases the friction.

This is an example of the geometrical amplification of friction, or how the layout of the books produces forces far beyond what is expected. Knots are another example, looping a rope around itself greatly increases the friction, resulting in a secure grip. The authors point out the recent resurgence of interest in this kind of problem and the general field of tribology, the study of surfaces in relative motion.

This is being driven by the need to understand the structure and behaviour of new micro and nano-engineered materials, which have impact on many aspects of life from medical applications to solar cells. Interleaved carbon nano-tubes as the material of the future anyone?