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No more lectures any more?

Try this introspective experiment. Think about your favourite quiz show and ask yourself how many questions you can remember after the programme ends (never mind the answers). You’ll find that you fall into one of two categories. Where the questions are in a subject you know about, you will probably remember quite a few. Where you do not know the subject, you will probably not recall many. There are two exceptions. If you are a contestant, you will probably remember everything word for word. And if you spot a mistake – like University Challenge quizmaster Jeremy Paxman struggling with quantum theory – you will probably not forget it.

So it is with lectures. In passive mode, students remember only what they already know. Occasionally, a lecturer might engage attention by tripping over his shoelaces or singeing her eyebrows. But lecturing is a spectator sport, and you do not learn to play mainly by watching. The arguments for improving lectures have been rehearsed in these pages on various occasions. Here I argue for a bit of humane culling and some redistribution of resources.

Before we go any further, let us agree on a few facts of life. First, the aim of a physics degree is not to provide students with a knowledge of physics. In the UK, at least, we are not merely training students to regurgitate lectures notes in handily sized examination packages. We regard a knowledge of physics as a means, not an end; we do not even necessarily see physics as a prelude to a career in physics. The purpose of a physics degree is, in essence, to train students to think the non-obvious in an appropriately rigorous manner.

Second, we want our students to be trained for life as independent learners because we know that, in the real world, few people spend any time learning much by means of lectures. So how do we achieve this? By occupying over half of the working week with lectures? I don’t think so.

Lecture problems

The preponderance of the traditional lecture as a way of communicating information is a relatively new phenomenon. Even recent techniques to make lectures more interactive have not changed their basic format. Indeed, study-skills manuals from the early part of the last century advised students going to university that they should initially expect relatively few lectures, because most material can be found in standard textbooks.

Lectures serve a useful social role, but in large doses they lead to a “lecture dependency”. This manifests itself as a tokenism, in which both teacher and taught go through the abstract ceremonial for an hour, inducing the satisfaction of devotions carried out. But it achieves little: the only people who benefit are the small number of students whose progress is almost teacher-independent.

In research it is difficult to be a revolutionary. This is because everyone is doing new things all of the time, if only to stop their competitors getting ahead in the next research-assessment exercise. In teaching, in contrast, it is very easy. Change anything at all and you are threatening the foundations of university life. New approaches to teaching therefore tend to be ghettoized. There is a good reason for this, namely that we lack a strong theoretical underpinning for different modes of teaching. However, in the absence of theory, let us try to create a few facts.

Some 15 years ago my colleagues and at Leicester University decided to abandon lectures for our courses on mathematical techniques for physics students. We found that the intelligent attention span of most students in maths lectures is a number that approaches zero. We decided instead to adopt a planned programme using textual material, exercise workshops and small-group teaching, with just a weekly lecture as an introduction to the current topic. For the last three years we have extended this approach to all of our core physics teaching.

Life without lectures

The basic plot is this. The traditional core “modules” in the first three years – mechanics, electricity and magnetism, etc – are each divided into four fortnightly “units” that follow the same basic pattern throughout the autumn and spring terms. Each consists of:

* an introductory lecture;

* one or more lectures devoted to problem solving after students have familiarized themselves with the material – with some multiple-choice computer-marked questions to encourage them;

* an exercise workshop with students working in groups with help from the staff team;

* a follow-up lecture based on experience in the workshop;

* small group sessions for feedback to students on marked work.

Each module totals about 100 hours and is taught by a team of three staff. The summer term is left free for revision classes.

So what’s new? After all, physics courses everywhere involve the equivalent of examples classes, tutorials and so on. Well, it certainly feels very different – in the same way that the same sum of money feels different if it is a debt or a credit. The material is designed to fit the number of hours of staff-student contact time, which occupy less than a third of the working week, so there is adequate (although not generous) time to go properly round the cycle of learning in each unit.

This cycle involves the acquisition of new knowledge, its assimilation, application and refinement or reflection. The structure of each unit is organized on this principle. As a result, staff and students have manageable tasks with immediate feedback. The responsibility can thus be put legitimately where it belongs: in the hands of the students.

Challenges and solutions

What are the problems of adopting this sort of approach? The news that the physics department has abolished lectures will certainly get round the rest of the university. The first you will know about this is when the pro-vice-chancellor for quality demands to know how your students are supposed to learn physics now that the physics department has given up teaching. You will also need to charm your university timetabling officer to schedule classes at times that are appropriate for the students, not when it is convenient for his or her computer. Finally, for a variety of reasons, the available textbooks are not entirely suitable for the task, so you will have to, as we did, produce some of your own material.

Apart from this we should talk of opportunities, not problems. The structure lets us help students to acquire “study skills”. For example, we run induction workshops where we advise students on how to make notes. It also allows us to integrate core skills such as time management, group work and oral communication into the physics teaching. Above all, however, it has given us the opportunity to incorporate an element of flexible pacing whereby the time that students spend on core material can be extended by up to 40% over two or three years, essentially without additional staff effort. There is no remedial teaching: students proceed at a (quantized) range of speeds through the core material.

But does it work? To help us find out, we employed a consultant from outside the university to carry out an initial evaluation of our new approach. By turning to an external person, we avoided the danger of hearing only what we wanted to. We also hoped that it would prevent us from broadcasting our failings within the university.

In the end, the consultant’s report was largely positive, although it highlighted various scheduling changes and other essential tweaks. And while a few students still find ways of spending a year without apparently learning very much, examination results have generally improved in an interesting way. What we have found is that even the weaker students now attempt the problem sections with some success, and do not just try to regurgitate what they have learned in their textbooks. This is a qualitative leap, not just a lowering of expectations, and it has improved the retention rate of students.

The more interesting evidence is, however, anecdotal. The staunchest defenders of our programme at the staff-student liaison committee meetings are now the third- and fourth-year students. But the story I most like comes from one of our new professors who came to Leicester from a prestigious institution and was impressed by the relative ability of his third-year project students here to get things done.

Do I therefore want the world to adopt our system? No. Whatever you do, do not copy us. What I would suggest, however, is that when constructing a teaching programme you should not think in terms of the solution (lectures) before you have specified the problem. Start from what you want to achieve and draw up a list of the teaching techniques available to achieve it. Then match the means to the ends in the most efficient way. You may be surprised at how much less the traditional lecture figures in the programme. And there is then no reason why those that remain should not all be brilliant.

Rock blasts in from the past

 

Rocks from space have had a bad press recently. The action movies Armageddon and Deep Impact explored what would happen if the Earth was threatened by a huge asteroid impact. Somewhat more down to Earth, so to speak, was a recent UK government report suggesting that we really should take the threat of an impact seriously. The authors of the report recommended that we increase our efforts to monitor near-Earth asteroids that may endanger our civilization, or at least wipe out a city, if these rocky masses were to hit.

Now Peter Brown from the University of Western Ontario in Canada and co-workers from Canada, the US and the UK have shown that space rocks are not all doom and gloom (Science 2000 290 320).

Chip off an old block

On 18 January this year, a six-metre-wide chip of an asteroid weighing 100 tonnes hurtled through space and smashed into the Earth’s atmosphere at 16 km s-1. Over 70 people were lucky enough to see the resulting fireball travel across northern Canada. The rock fragmented in the atmosphere, scattering pieces across an area 16 km long and 2 km wide. Far from wiping out civilization, this impact missed everyone, and may now help us to figure out the origins of the Earth and of the life on it.

Once any extraterrestrial material lands on Earth, it is called a meteorite. This latest example fell near Carcross in the Yukon, and the recovered fragments were found on the frozen surface of nearby Tagish Lake. A few days later, local man Jim Brook went out onto the lake and picked up some of the frozen pieces of the meteorite. Being a keen amateur astronomer, he knew to collect the fragments without touching them, a point that proved crucial when the importance of this rock to astrobiology was later established. The Tagish Lake meteorite turned out to be unique. It appears to be one of the most pristine examples of early solar-system material that meteorists have ever studied.

Like about 4% of all meteorites, Tagish Lake – as the rock itself is called – is one of the carbonaceous chondrites, a group of meteorites that are relics from pre-planetary times in the solar system. But when viewed in more detail, it differs from all other known meteorites.

Tagish Lake has a similar chemical composition to meteorites known as CI1s, which are made from the same elements as the Sun minus the hydrogen and helium. Chemically speaking, CI1 meteorites have changed the least since they accreted from solar material at the beginning of the solar system, just under 5000 million years ago. But CI1s are not completely unscathed by their long history. They contained a lot of water when they formed, which usually completely permeates and destroys their original features and textures.

In contrast, Tagish Lake has not been so severely affected by water damage. It is more like another meteorite type, called CM2, than CI1 in appearance. CM2 meteorites have preserved much of their original textures. For example, they contain rounded fragments called chondrules, which are thought to be among the oldest solid particles to form around the Sun. Brown and co-workers have found that Tagish Lake also contains chondrules.

In other words, Tagish Lake uniquely contains both the primitive textures of CM2s and the primitive chemical composition of CI1s. It may be the first hybrid of these two meteorite groups, and Brown and colleagues have suggested it should be classified as a CI2. That means this precious sample may be the most unaltered sample of early solar-system material we have ever been able to hold.

Studying the age, chemical and isotopic composition, and the mineralogy of the meteorite will show us – perhaps better than any other rock we have in the world’s museum collections – how the early solar system evolved from a young star with a dusty disk to the Sun and planets we know today.

The meteorite is also unusual in its carbon content. It contains 5.4% carbon, more than any other known meteorite. This carbon is mainly in the form of carbonate minerals and organic compounds. Meteorites like these may have been critical to the evolution of life on Earth, bringing the basic building blocks of life to the surface of our planet billions of years ago. Studying this meteorite may provide us with vital clues to how life formed here, and perhaps how it may form in other places in the galaxy as well.

A dream come true

The meteorite could not have fallen at a better time. Over the last few years interest in the new field of astrobiology has soared. In 1996 NASA researchers suggested that a meteorite from Mars, ALH 84001, contained evidence for ancient bacteria.

Years of controversy have followed this allegation. Some scientists believe that ALH 84001 contains terrestrial organic impurities, rather than indigenous bacteria. Further work showed, in fact, that all meteorites become easily contaminated once they fall to Earth. Many researchers believe that contamination is almost inevitable, especially for meteorites that are particularly rich in carbonaceous material that provides a good source of food for bugs. The cause and effects of terrestrial contamination on extraterrestrial material is now being studied extensively, not just for meteorites but also for future sample-return space missions.

The Tagish Lake meteorite was like a dream come true for astrobiologists, as it fell in a frozen, almost-sterile area, and was quickly and expertly collected. The meteorite has since been kept frozen under controlled conditions to ensure that the carbonaceous material is altered as little as possible before analysis. Although the organic characterization is not yet complete, it is likely to show us exactly what the original building blocks of life were.

Tagish Lake serves as a reminder that rocks from space are not all bad. Although they can – and will – wipe out entire species (just ask the dinosaurs), they may also have given life to our planet in the first place. Perhaps it is time we celebrate these celestial gifts, as well as fear them.

Green light for nanomotors

Schmid and colleagues used new microscopy techniques to observe in real time interactions between the tin clusters – each containing hundreds of thousands of atoms – and the copper surface. They found that tin and copper atoms swap places at the interface between the two metals to form bronze. The tin atoms in the cluster strongly repel those already incorporated into the copper. The need to lower the surface free energy drives the tin islands towards fresh patches of copper, leaving ‘snail trails’ of bronze behind them. This two-dimensional alloying process represents a motor because it converts chemical energy into motion.

The motion of clusters on the copper surface is surprisingly complex. Schmid’s team noticed that, far from moving in a random fashion, the clusters tended to follow ordered paths and only crossed old tracks when there was no alternative. The researchers were able to vary the speed of the clusters – which, weight-for-weight, produce about three times more power than a car – by adjusting the temperature. The clusters gradually shrink and disappear when all of the tin has dissolved into the copper.

Tin is usually reluctant to dissolve into copper because its atoms are much bigger. Schmid and colleagues overcame this problem by using a copper crystal cleaved along the plane containing most defects – which accommodates the tin atoms more easily. Two-dimensional alloying also takes place much more readily than alloying in bulk materials.

The phenomenon is a nanoscale version of one first seen by Lord Rayleigh in the 19th century. Rayleigh determined the surface tension of water by observing the motion of camphor particles across water driven by the surface free energy.

Louis Néel and Lochlainn O’Raifeartaigh

Louis Néel was born in Lyons in 1904 and dedicated his career to the study of magnetism. In 1932 he discovered antiferromagnetism – a form of magnetism in which the ‘spins’ on neighbouring atoms point in opposite directions. Previously only three forms of magnetism – dia-, para- and ferromagnetism – were known. During the Second World War, Néel worked on the defence of French war ships against German magnetic mines.

In 1940, he set up the Laboratoire d’Electrostatique et de Physique du Métal, which six years later became part of the Centre National de la Recherche Scientifique in Grenoble. He went on to share the 1970 Nobel Prize for his discovery of antiferromagnetism, which has formed the basis of modern magnetic theories. He received dozens of awards during his career and was honoured by France, the Netherlands, Germany, Romania, the UK, and the US. Néel died on 17 November.

Lochlainn O’Raifeartaigh was born in Dublin in 1933 and was associated with the Dublin Institute for Advanced Studies for most of his career. His research concentrated on the applications of group theory to physics, gauge theory and supersymmetry. He made his name in the mid-1960s with a “no-go” theorem which showed that the imposition of a certain symmetry group on a theory would allow for the possibility of a unified description of particles with different internal symmetries.

In later life he became renowned for his work on the history of gauge theory and one of his last publications was an article on this subject in Reviews of Modern Physics (vol. 72 pp 1 – 23). He also wrote several books on gauge theory and recently received the Wigner medal for his “pioneering contributions to particle physics.” He died on 18 November.

Good news for UK physics

“This budget is seriously good news for UK physics,” Ian Halliday, PPARC chief executive, told PhysicsWeb. “It has provided PPARC’s first real budget increase for 20 years.” This contrasts with the last round of spending two years ago when PPARC was the only research council not to receive a real-terms rise in funding.

The Engineering and Physical Sciences Research Council has done well in the strategic areas of the budget. Over the three years of the spending review it will receive £41m for basic technology, which will cover work in areas such as quantum computing, photonics and nanotechnology. It will also get £32m for e-science and £13m for genomics. However, it will receive only a £17m increase across its core programme areas.

Joining ESO was considered a top priority for UK astronomy following a recent long-term review of PPARC science, because it will give astronomers access to four 8-metre telescopes in Chile and will ensure that astronomers are involved in the next generation of even larger facilities. Under current proposals, the UK will become a member of ESO in 2002, following final negotiations in the interim, but the £70m joining fee and £12m annual costs will mean PPARC having to make cut backs in other areas.

PPARC will use its money for computing to develop the ‘Grid’, a way of processing huge volumes of data such as those that will be produced by the Large Hadron Collider when it comes on line at CERN in 2005. It will involve distributing data to a network of computers around the world and is being touted as the successor to the Web. PPARC will also fund a similar project in astronomy called the ‘Astro-grid’, which is being designed to combine vast amounts of astronomical data and images from a range of international ground and space-based telescopes.

Descartes prize applauds European cooperation

Dago de Leeuw, a physicist at Philips Research Laboratories in the Netherlands, leads a team of physicists recognized for their pioneering research in plastic electronics. De Leeuw and colleagues from The Netherlands, Denmark, Germany and the UK developed a new class of transistors based on polymers. The transistors are strong but flexible and are cheaper than conventional silicon-based devices.

Ian Smith, a chemist at the University of Birmingham, heads an Anglo-French group recognized for its investigations into chemistry near absolute zero. Smith and co-workers observed reactions taking place at temperatures never before achieved in the laboratory. Their work provides insights into processes inside the galactic clouds of gas and dust in which new stars form.

A jury of eminent scientists selected three winners from a hundred pan-European teams. Genetics research led by Alan Lehmann at the University of Sussex also took a share of the prize.

First light on silicon laser

The internal energy levels of bulk silicon – in particular its ‘indirect bandgap’ – makes it emit light very inefficiently. Existing lasers are therefore based on ‘direct’ bandgap materials like gallium arsenide, which readily emit light. But these materials are expensive and difficult to integrate into the silicon chips used throughout the electronics industry.

Pavesi and co-workers sandwiched silicon nanocrystals between layers of oxidized silicon and excited the structure with green laser light. The device then emitted a much more intense beam of red light – representing a degree of amplification similar to lasers based on direct bandgap materials. Pavesi’s team believes that the interface between the silicon nanocrystals and the oxidized silicon is responsible for the success of its device. The electronic interactions that take place at the boundary appear to create many light-emitting states.

But the light is incoherent – that is, the photons are out of phase – and coherent light is a prerequisite for laser emission. A commercially viable silicon laser would also need to be electrically stimulated – rather than by another laser – for easy inclusion in microcircuits. Future investigations will focus on different configurations and topologies of silicon nanostructures in an attempt to find even more efficient light-emitting mechanisms.

US science awards recognize physics

The US Government makes another presentation next week with the National Medal of Science awards on 1 December. Physicists Willis Lamb and Jeremiah Ostriker receive the medal. Lamb, of the University of Arizona, won the 1995 Nobel Prize for experimental work on hydrogen that revealed a new quantum relativistic effect. His work became one of the foundations of quantum electrodynamics. He also pioneered the field of laser physics. Ostriker, of Princeton University, is recognized for his contributions to astrophysics that revolutionized concepts of the nature of pulsars, the sizes and masses of galaxies, and the nature and distribution of matter in the universe.

Datz, 73, began his career as a research chemist at the Oak Ridge National Laboratory in 1953 and worked on atomic and molecular physics. Drell, 74, was deputy director of the Stanford Linear Accelerator Center until 1998. Drell is an arms control expert and has advised the US government on technical defence matters. York, 78, is a nuclear physicist and director of the University of California’s Institute on Global Conflict and Cooperation. He was science advisor to the US Government and negotiated the Comprehensive Test Ban Treaty under President Carter.

Enrico Fermi’s pioneering work in the field of atomic physics earned him the first award in 1954, which became an annual event two years later. The prize celebrates the lifetime contributions of scientists in areas of energy science and technology that have benefited humanity.

Complex fluids go through a strange phase

Some liquids are very useful because their molecules act as tiny dipoles that can be aligned by electric or magnetic fields. Vehicle clutches, ink-jet printers and lubricants are among the applications that make use of these so-called dipolar fluids, which consist of micron-sized spherical particles suspended in a fluid. But to exploit the liquids further, scientists need a better understanding of how they behave. “Understanding phase separation in these liquids will allow us to predict whether they will remain homogeneous under certain conditions”, Safran told PhysicsWeb. “This is crucial for the development of new applications for dipolar fluids”.

In these dipolar liquids, the colloidal particles line up head-to-tail to form long chains, rather like polymers. This tends to prevent fluids behaving in a simple manner. But Tlusty and Safran found that the key to understanding the fluid was to treat the chains, rather than the individual molecules, as the basic unit of the liquid. The pair developed a simple model of the actions of a dipolar fluid at different temperatures. In a simple fluid, the liquid and gas phases are easily distinguished by their greatly differing concentrations. But Tlusty and Safran found that different phases in the dipolar fluid are rather unusual in that they also have very distinct topologies. Impurities in the dipolar liquid caused Y-shaped branches and ‘loose ends’ to form in the chains. The model showed that under certain conditions, the liquid separates into a dense network of chains and a dilute ‘gas’ of loose ends.

The separation of the fluid into the two phases will affect the overall viscosity of the fluid. “We need to take into account local fluctuations next”, said Safran. “This will give us an even greater insight into the complexities of these fluids”.

Magnetism’s standard model gets a facelift

The standard model – developed by Pierre Weiss in 1907 – treats paramagnets as systems of non-interacting magnetic dipoles. The theory successfully describes the behaviour of paramagnets – materials that become weakly magnetized inside an applied magnetic field – but cannot account for ferromagnets. Ferromagnets are strongly magnetic even when there is no external field, but the magnetism disappears above a critical temperature known as the Curie temperature.

According to the standard model, Curie temperatures should be much lower than they actually are. Weiss therefore proposed the existence of strong attractions among the dipoles – later found to be quantum ‘exchange interactions’ between atomic spins – to account for the discrepancy. The fix worked, but the model was still unable to predict accurately the behaviour of ferromagnets around the Curie temperature and at very low temperatures.

The simplicity of the standard model has made it popular and worthy of further refinement. Chamberlin addressed the blind spot by including the effects of nanothermodynamics – thermodynamic effects that cause magnetic fluctuations on a molecular scale. “I became intrigued by the similarities in the behaviour of glasses and magnets”, Chamberlin told PhysicsWeb. “The breakthrough came when I noticed that essentially the same law describes the liquid-glass and the paramagnetic-ferromagnetic transitions”.

The amended standard model now accurately describes ferromagnetism across the whole temperature range for the first time. Previous attempts to develop more accurate theories have had only limited appeal because they focused on narrow temperature ranges.

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