Hurricanes create large ocean waves, which send energy pulsing through the Earth as they pound the shoreline. To determine the power of Katrina's seismic waves, Peter Gerstoft of the University of California, San Diego, and colleagues analysed the signals recorded by a network of 150 seismic stations in southern California just before Katrina hit the Louisiana coast. They used a method known as beamforming, which preferentially picks up signals from a particular direction, to decipher the seismicity generated by Katrina (Geophysical Research Letters, vol 33, p L17805).

Seismic surface waves, which travel through the Earth's crust, were detected 30 hours before the hurricane made landfall, while body waves, which bounce down into the mantle, arrived some 18 hours later. "The body waves had travelled down to 1100 kilometres inside the Earth," Gerstoft says. This is the first time that a hurricane's seismic signal has been detected so far away.

There are many reasons for this sudden excitement surrounding "biofuels" (see "Biofuel basics", beneath this article, for a look at exactly what this covers). Not only have soaring oil prices made biofuels economically viable for the first time in years, but they could also help countries reduce their dependency on fossil fuel imports. However, the real PR coup for biofuels is their eco-friendly image.

Supporters claim they will dramatically slash our net greenhouse gas inputs, because the crops soak up carbon dioxide from the atmosphere as they grow. Given this, it's no surprise politicians and environmentalists the world over are backing the idea, hoping we will all soon be using this green alternative to power our cars, buses and trains. Even former oilman President George W. Bush is behind them. In his State of the Union address on 31 January, he called for a national drive to run vehicles on biofuels.

But before you join in the celebrations, all is not as it seems. Scientists have begun to question the environmental and social arguments for bioethanol and biodiesel (see "Biodiesel backlash"), casting serious doubts on whether either can meet such high hopes. And environmentalists find themselves in a particularly excruciating quandary, with half the green community embracing biofuels to the last corn kernel, and the other half desperate to slam on the brakes.

Far from solving our problems, say the dissenters, biofuels will trash rainforests, suck water reserves dry, kill off species and raise food prices. They will also accelerate the corporate takeover of agriculture, create famines and could leave fuel importers as dependent as ever on other countries. Worst of all, many biofuels will barely slow global warming at all if the technology behind them does not improve. The biofuels supporters counter that it's still early days, and we should give this technology the time and investment to deliver on its promise. So who's right?

The controversy may be brand new, but biofuels themselves are an old idea. The Model T Ford, first produced in 1908, was designed to run on ethanol, and Rudolf Diesel, who invented the diesel engine in 1892, ran his demonstration model on peanut oil. Biofuels fell out of favour as petroleum-based fuels appeared and became cheaper to produce, but after the oil crisis of the early 1970s, some countries returned to biofuels. For example, Brazil has been producing large quantities of ethanol from sugar cane for over 30 years, and last year produced about half of the world's bioethanol (see Graphic). Brazilian law now requires that 20 per cent of fuel at the pumps be blended with bioethanol, which all gasoline-powered cars can tolerate. Over 15 per cent of Brazil's cars can even run on pure bioethanol.

According to a study published in June by the Worldwatch Institute, for Brazil to produce 10 per cent of its entire fuel consumption requires just 3 per cent of its agricultural land, so it's not surprising other places want to emulate Brazil's approach. The problem is that in most other countries, the numbers don't add up.

The same Worldwatch study estimated that to meet that 10 per cent target, the US would require 30 per cent of its agricultural land, and Europe a staggering 72 per cent. It's no secret why things stack up so differently. Not only do Brazilians drive far less than Europeans and Americans, their fertile land and favourable climate mean their crop yields are higher, and their population density is lower.

The US and Europe aren't the only ones hoping the Brazilian model will be a quick fix for environmental and fuel-security woes. China plans to cut oil imports and CO2 emissions by running its cars on ethanol made from cassava, while Cuba hopes to revitalise its moribund sugar industry by turning the crop into ethanol, and Hungary wants to replace Russian energy imports with corn-based ethanol.

What few yet appreciate is that biofuels are not all made equal. In the US, the immediate plan is to ramp up production of corn bioethanol. America's 100th corn-to-ethanol distillery came online in May, and a further 30 are under construction across the Midwest. Bioethanol production is forecast to almost double between 2005 and 2007, by which time the bioethanol business will be consuming around a fifth of the US corn crop. But when you try to assess the environmental benefits of bioethanol, things are not clear-cut. It takes a lot of energy both to grow corn and to convert it to ethanol, and cultivating a crop demands large quantities of fertiliser and pesticides, which themselves have environmental and energy costs. So is it actually worth it?

Several research groups have tried to take all this into account and compare fossil fuel emissions with those of corn bioethanol at every stage of production from seed to engine. The studies have been beset by scientific uncertainties, such as how much of the greenhouse gas nitrous oxide is produced by the nitrogen fertiliser used in growing corn. Opinions are divided as to what should and should not be included in the calculation, which means the results vary widely, but one study by David Pimentel at Cornell University in New York concluded that corn ethanol creates more greenhouse gases than burning fossil fuels.

Others aren't so pessimistic. In a review of several studies published in Science in January, Alexander Farrell of the University of California, Berkeley, estimated bioethanol would produce 13 per cent less greenhouse emissions than an equivalent amount of gasoline. However, Farrell arrives at this more favourable figure by assuming the leftover biomass from making the bioethanol is used as a dry fuel in a furnace or fed to animals, and not all bioethanol refineries do this.

Another reason a growing number of people oppose biofuels is that growing corn for ethanol uses up land that is currently supplying food to the world. Americans won't go hungry if surplus US corn is converted to ethanol rather than exported, but the resulting slump in the global grain supply will precipitate a rise in prices, and many see that as unethical. According to Lester Brown, veteran commentator and activist on food politics, the corn required to fill an SUV tank with bioethanol just once could feed one person for a year. He describes the boom in bioethanol as a competition between the 800 million people in the world who own automobiles and the 3 billion people who live on less than $2 a day, many of whom are already spending over half their income on food.

According to the UN Food and Agriculture Organization, the competition has already begun. The FAO says the conversion of corn to ethanol is a primary reason for a sharp decline in world grain stocks and a commensurate rise in grain prices in the first half of 2006. The trend was echoed in a report to investors by the bank Goldman Sachs in July, which predicted corn prices will rise further as biofuels grow. Eric Holthusen, a senior official with oil giant Shell, recently described using food crops to make fuel while people were starving as "morally inappropriate".

It is striking how much land will be needed for biofuels to make a significant contribution to fuel usage. In a paper published in the Proceedings of the National Academy of Sciences in July, Jason Hill and colleagues at the University of Minnesota, St Paul, calculated that even if the US diverted its entire current corn harvest to biofuels it would meet only 11 per cent of its current gasoline demand. The Worldwatch Institute estimates that to produce 10 per cent of the world's transport fuels would require 9 per cent of the planet's agricultural land.

Promoters of biofuels say such calculations are misleading. They claim high prices stimulated by demand for biofuels will encourage both more intensive cultivation of corn and the spread of corn fields onto land that is now idle. Unfortunately, both scenarios would undermine the already slender climate benefits of corn-based ethanol. More intensive growing means more chemical inputs, increasing the energy consumption and greenhouse emissions per tonne of corn. And Hill points out that clearing and ploughing virgin land will also release more CO2, quite possibly resulting in a net increase in greenhouse emissions from biofuel production.

So much for corn, but could other crops fare better? Lawrence Eagles at the International Energy Agency in Paris, France, says making ethanol from sugar cane is better for the environment than using corn because it avoids the first phase of the corn process - converting the plant starch into sugar. In terms of litres of fuel per hectare of crop, and net greenhouse gas benefit, sugar cane beats corn, says Eagles.

Some bioethanol producers have caught on to the idea. As a result, world sugar prices have doubled in the past 18 months, says Richard Oxley, head of industry consultancy Sugaronline. "All the major producers round the world - Brazil, India, Thailand, etc - are just rushing out and planting as much cane as they can," he says.

Trouble is, the high price is encouraging growers to clear land and plant sugar cane without regard for the ecological impact. Environmentalists fear that as demand for sugar cane rises on the global market, Brazilian farmers will push ever deeper into the Amazon rainforest, either to grow sugar cane itself or crops displaced by it.

As if that weren't enough, sugar cane plantations put huge pressure on water supplies - this is a thirsty crop. In countries without plentiful rainfall, farmers must draw water from rivers or underground reserves. So although irrigation isn't a problem in Brazil, other countries aren't so lucky. For example, in the Indian state of Maharashtra, farmers are scrambling to grow more cane to take advantage of the high prices, yet existing plantations already take two-thirds of the state's water and have lowered water tables by up to 50 metres in places.

Globally, no one is considering how much water biofuels will require, says Oxley. India is already drawing down its water reserves fast, and this will lead directly to dry wells, parched fields and empty granaries. While sugar cane may be a more greenhouse-friendly feedstock than corn for making ethanol, it is markedly worse in terms of its demands on the world's dwindling water reserves.

So are we utterly mistaken to think that bioethanol could usher in an era of greener energy? The way things are developing, it certainly looks that way, but it needn't be so.

The technology for producing biofuels is still in its infancy, and scientists working on it have grander things in mind. They want to perfect a way to make biofuels from non-food crops and waste biomass, saving the corn and other fuel crops for food use, and to do it without wrecking natural ecosystems. Given time, they think they can achieve this.

Already researchers are discovering clever ways to produce bioethanol without using food crops, and focusing instead on converting cellulose-rich organic matter into ethanol. Cellulose is the main structural component of all green plants. Its molecules comprise long chains of sugars strong enough to make plant cell walls. If you could break down those molecules to release the sugars they contain, you could ferment them into ethanol.

Developing an efficient process to convert cellulose into ethanol could open the door to many non-food materials such as switchgrass - a wild grass that thrives in the eastern states and Midwest of the US - straw, crop residues like stalks and hardwood chips. Its supporters say cellulose feedstocks could deliver twice as much ethanol per hectare as corn, and do it using land that is today neither economically productive nor environmentally precious. Some think municipal waste such as paper, cardboard and waste food could even be used as a feedstock.

A road map to making ethanol from cellulose set out in June by the US Department of Energy estimated the US could produce a third of its fuel needs in this way by 2030. It recommends genetically modifying crops such as switchgrass and poplar to make hardy, pest-resistant varieties that are very high in cellulose. This would mean low-maintenance feedstock, dramatically cutting energy and chemical inputs compared with existing feedstocks. The catch is that it would also require much more efficient enzymes to break the cellulose down into sugars, and better varieties of yeasts that ferment the sugars into ethanol faster and more efficiently than existing strains. "We can engineer crops to grow on dry and saline soil. This is going to be a revolution. For agriculture it is going to be a very exciting time," says Raymond Orbach, Under Secretary for Science at the DoE.

But so far most companies have been hesitant about investing in the research necessary to tackle these problems. So the DoE is setting up two new research centres, into which it will plough $250 million over the next five years, with the aim of developing the next generation of biofuel feedstocks. "It's too risky for the private sector. That's why government is doing this," says Orbach.

But one Canadian company is already on the case. Iogen, based in Ottawa, has built a pilot plant that has been producing cellulose ethanol in small quantities for the last two years. It uses a tropical fungus genetically modified to produce enzymes that break down cellulose, and can "digest" all sorts of biomass.

ogen recently attracted investment of $30 million from Goldman Sachs, and in January it announced it would investigate the feasibility of building a full-scale commercial plant in Germany in partnership with Volkswagen and Shell. If the numbers add up, Iogen could kick-start the revolution that may yet deliver us from our dependence on oil, without costing the Earth in the process.

From issue 2570 of New Scientist magazine, 25 September 2006, page 36-41

Of course, laws of nature are very useful, and we have in fact been able to discover good candidates for them. But to believe a law is useful and reliable is not the same thing as to believe it is eternally true. We could just as easily believe there is nothing but an infinite succession of approximate laws. Or that laws are generalisations about nature that are not unchanging, but change so slowly that until now we have imagined them as eternal.

These are disturbing thoughts for a theoretical physicist like myself. I chose to go into science because the search for eternal, transcendent laws of nature seemed a lofty goal. However, the possibility that laws evolve in time is one that recent developments in theoretical and experimental physics have forced me, and others, to consider.

The biggest reason to consider that the laws of nature might evolve is the discovery that the universe itself is evolving. When we believed that the universe was eternal it made more sense to believe that the laws that governed it were also eternal. But the evidence we have now is that the universe - or at least the part of it we observe - has been around for only a few billion years.

We know that the universe has been expanding for about 14 billion years and that as we go back in time it gets hotter and denser. We have good evidence that there was a moment when the cosmos was as hot as the centre of a star. If we use the laws that we know apply to space-time and matter today, we can deduce that a few minutes earlier the universe must have been infinitely dense and hot. Many cosmologists take this moment as the birth of the universe and indeed as the birth of space and time. Before this big bang there was nothing, not even time.
Why these laws?

So what could it mean to say that a universe only 14 billion years old is governed by laws that are eternally true? What were the laws doing before time and space? How did the universe know, at that moment of beginning, what laws to follow?

Perhaps the solution to this is that the big bang was not the first instant of time. However, this raises a new question, which has been championed by the great theoretical physicist John Wheeler. Even if we believe the universe evolved from something that existed before the big bang, we have no reason to believe the laws of that previous universe were the same as those we observe in our universe. Might the laws have changed when our universe, or region of the universe, was created?

This question came to the fore in 1973, when physicists first developed a theory of elementary particle physics called the standard model. This theory has successfully accounted for every experiment in particle physics before and since that time, apart from those that involve gravity. It only required a small modification to incorporate the later discovery that neutrinos have mass. As for gravity, all experiments support the general theory of relativity, which Einstein published in 1915. There may be further laws to discover, to do with the unification of gravity with quantum theory and with the other forces of nature. But in a certain sense, we have for the first time in history a set of laws sufficient to explain the result of every experiment that has ever been done.

As a result, in the past three decades the attention of physicists has shifted from seeking to know the laws of nature to a new question: why these laws? Why do these laws, and not others, hold in our universe?

Confronting this question while working on string theory in the 1980s, a few of us began to wonder whether the laws might have changed at the big bang, just as Wheeler had suggested. It was obvious that we could make a connection to biology. I wondered whether there might be an evolutionary mechanism that would allow us to answer the question of "why these laws?" in the same way that biology answers questions like "why these species?". Perhaps the mechanism that makes laws evolve also picks out certain laws and makes them more probable than others. I found such a mechanism, modelled on natural selection, which I called cosmological natural selection.

This is possible because string theory is actually a collection of theories: it has a vast number of distinct versions, each of which gives rise to different collections of elementary particles and forces. We can think of the different versions of string theory as analogous to the different phases of water - ice, liquid and steam. When the universe is squeezed down to such tremendous densities and temperatures that the quantum properties of space-time become important, a phase transition can take place - like water turning to steam - leading from one version of the theory to another.

The many different phases of string theory can also be seen as analogous to a variety of species governed by different DNA sequences. They can be imagined as making up a vast space, which I called the "landscape", to bring out the analogy to a "fitness landscape" in biology that represents all possible ways genes can be arranged.

Cosmological natural selection makes a few predictions that could easily be falsified, and while it is too soon to claim strong evidence for it, those predictions have held up (New Scientist, 24 May 1997, p 38). At the very least, it opened my eyes to the possibility that a theory in which the laws changed in time could still make testable predictions.

It turns out that I had been beaten to the punch: some philosophers had confronted these issues over a century ago. In 1891 the philosopher Charles Pierce wrote that it was hardly justifiable to suppose that universal laws of nature have no reason for their special form. "The only possible way of accounting for the laws of nature, and for uniformity in general, is to suppose them results of evolution," he added.

Pierce went much further than I have done, asserting that the question "Why these laws?" has to be answered by a cosmological scenario analogous to evolution. But was he right?

Let us start with an obvious objection: if laws evolve, what governs how they evolve? Does there not have to be some deeper law that guides the evolution of the laws? For example, when water turns into ice, more general laws continue to hold and govern how this phase transition happens - the laws of atomic physics. So perhaps, even if a law turns out to evolve in time, there is always a deeper, unchanging law behind that evolution.
Shapes of things to come

Another example concerns the geometry of space. We used to think that space always followed the perfectly flat Euclidean geometry that we all learn in high school. This was considered one of the laws of nature, but Einstein's general theory of relativity asserts that this is wrong. The geometry of space can be anything it wants to be: any of an infinite number of curved geometries is possible. So what picks out the geometry we see?

General relativity asserts that the geometry of space evolves in the course of time according to some deeper law. Today's geometry is what it is because it evolved from a different geometry in the past, following that definite law.

However, there is a big problem with this kind of explanation, which has to do with the fact that the laws that govern the evolution of geometry are deterministic. They share this feature with most laws studied in physics, including Newton's laws and quantum mechanics. Consider Newton's law of motion for an object. If we know where the object is now and how it is moving, and we know the laws that govern the forces it encounters, we can predict where it will be and has been for all time, past as well as future. General relativity is the same. If we know the geometry of space at a particular time, and how it is changing, we can predict the whole history of space-time. To apply these deterministic laws, however, we have to give a description of the system at one point in time. This is called the initial condition. If we do not specify an initial condition, the laws cannot describe anything.

This is why Einstein's equations do not fully explain why the geometry of space is what it is. They require an initial condition -the geometry at an earlier time. This brings us back to the dilemma about the big bang. Either the universe had no beginning, in which case the chain of causes goes further into the past, before the big bang; or the big bang was the beginning, and we require some explanation as to why it started and with what geometry.

So we have arrived at a conundrum. It appears that if laws evolve, other laws are required to guide their evolution. But then, the evolution of a law is just like the evolution of any other system under a deterministic law. We cannot explain why something is true in the present without knowing its initial state. Applied to laws, this means we cannot explain what the laws are now if we do not specify what the laws were in the past. So the idea of laws evolving by following a deeper rule does not seem to lead to an explanation of "why these laws?".

To avoid this we need an evolutionary mechanism that will allow us to deduce features of the present without having to know the past in detail. This is where Pierce's statement, which appears to invoke biological evolution, comes into its own.

In biology, many features of living organisms can be explained by natural selection, even if one doesn't know details about the past. As the process is partly random, we cannot predict exactly what mix of species will evolve in a given ecosystem, but we can predict that the species that survive will be fitter than those that don't. This is, I believe, why Pierce insisted that any explanation of "why these laws?" involves evolution. And using this kind of logic, cosmological natural selection makes some predictions without detailed information about previous stages of the universe.

But even this is unsatisfactory: it doesn't address the question of how a law that guides the evolution of matter in time could also change in time. For that, we have to examine the way we think about time.

There are big problems with time, even before we start thinking about the evolution of laws of nature. Nowhere is this more apparent than in the field of quantum gravity, which attempts to pull quantum theory and general relativity together into one consistent framework. This is because the two theories each use a different notion of time. In quantum theory, time is defined by a clock sitting outside the system being modelled. In general relativity, time is measured by a clock that is part of the universe that the theory describes. Many of the successes and failures of different approaches to quantum gravity rest on how they reconcile this conflict between time as an external parameter versus time as a physical property of the universe.

However these questions are eventually resolved, there are still deeper issues with time. These arise in any theory in which the laws are taken as being eternal. To illustrate this, we can take a simple example, such as Newton's description of a system of particles. To formulate the theory we invent a mathematical space, consisting of all the positions that all the particles might have. Each point in the space is a possible configuration of the system of particles, so the whole space is called the configuration space. As the system evolves over time, it traces out a curve in configuration space called a history. The laws of physics then pick out which histories are possible and which are not.

The problem with this description is that time has disappeared. The system is represented not by its state at a moment of time but by a history taking it through all time. This description of reality seems timeless. What has disappeared from it is any sense of the present moment, which divides our experience of the flow of time into past, present and future. This problem became particularly acute when it emerged in Einstein's theory of general relativity. Solving the theory gives a four-dimensional space-time history and no indication of "now".

Some, looking at this picture, have been tempted to say that reality is the whole timeless history and that any sense we have of a present moment is some kind of illusion. Even if we don't believe this, the fact that one could believe it means that there is nothing in this description of nature that corresponds to our common-sense experience of past, present and future. This is called the problem of transience. The sense of the universe unfolding or becoming in time, of "now", has no representation in general relativity. But in truth the problem was always there in Newton's physics and it is there in any theory in which some part of nature is described by a state that evolves deterministically in time, governed by a law that dictates change, but never changes.
The illusion of now

The philosopher Roberto Unger of Harvard University calls this the "poisoned gift of mathematics to physics". Many believe that mathematics represents truth in terms of timeless relationships, based on logic. It allows us to formulate physical laws precisely: this is the gift. By doing so, however, mathematics represents paths in configuration space unfolding in time by logic, and this logic exists outside of time. The poison in the gift is the disappearance of any notion of the present or of becoming.

Physicists and their predecessors have been eliminating time like this since the days of Descartes and Galileo at least. But is it the wrong thing to do? Is there a way to represent change through time in a way that represents our sense of becoming, or of time unfolding?

I don't know the answer, but I suspect this question is connected to that of whether laws can evolve in time. One can only draw the curve representing a history in time by assuming that the laws which govern how the history evolves never change. Without a fixed, unchanging law, one could not draw the curve.

Here is the question that keeps me awake these days: is there a way to represent the laws of physics mathematically that retains the notions of the present moment and the continual unfolding of time? And would this allow us - or even require us - to formulate laws that also evolve in time?

Again, I don't know the answer, but I know of a few hints. One comes from theoretical biology. The configuration space for an evolutionary theorist is vast, consisting of all the possible sequences of DNA. At present, there is a particular collection representing all the species that exist. Evolution will produce new ones, while others will disappear. The interesting thing is that natural selection operates in such a way that biologists have little use for the entire configuration space. Instead, they need study only a much smaller space, which is those collections of genes that could be reached from the present one by a few evolutionary steps. The theoretical biologist Stuart Kauffman of the University of Calgary in Alberta, Canada, calls this the "adjacent possible".

This scheme allows laws to change. Consider the laws that govern sexual selection. They do not make sense for any old biosphere, as they only come into play when there are creatures with two sexes. So in evolutionary theory there is no need for eternal laws, and it makes sense to speak of a law coming into existence at some time to govern possibilities that did not exist before. Furthermore, there is such a vast array of possible mechanisms of natural selection that it would not make any sense to list them all and treat them as timeless. Better to think of laws coming into existence as the new creatures that evolve in each step require.

Of course, one might reply that natural selection itself never changes. But natural selection is a fact of logic, not a contingent law of nature. Every real law in biology depends on some aspect of the creatures that exist at a given time, which means the laws are also time-bound.

It is not impossible to achieve time-bound laws in physics. There are logicians who have proposed alternative systems of logic that incorporate a notion of time unfolding. In these logics, what is true and false is assigned for a particular moment, not for all time. For a given moment some propositions are true, others false, but there remains an infinite list of propositions that are yet to become either true or false. Once a proposition is true or false, it remains so, but at each moment new propositions become decided. These are called intuitionalist logics and they underlie a branch of mathematics called topos theory.

Some of my colleagues have studied these logics as a model for physics. Fotini Markopoulou of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, has shown that aspects of space-time geometry can be described in terms of these logics. Chris Isham of Imperial College London and others propose to reformulate physics completely in terms of them.

It is interesting that some physicists now propose that the universe is some kind of computer, because similar questions are being asked in computer science. In the standard architecture all computers now use, invented by the mathematician John von Neumann, the operating system never changes. It governs the flow of information through a computer just as an eternal law of nature is thought to guide physics. But some visionary computer scientists such as Jaron Lanier wonder whether there could be other kinds of architectures and operating systems that themselves evolve in time.

Looking at biology, it seems there are advantages to what are, essentially, time-bound laws. Evolving laws might make computer systems similarly robust and less likely to do what the laws of natural selection, it seems, never do: crash. The universe, too, seems to function rather well, operating without glitches and fatal errors. Perhaps that's because natural selection is hard at work in the laws of nature.

From issue 2570 of New Scientist magazine, 21 September 2006, page 30-35

Perennial sea ice is the ice that survives at least one summer, and is usually more than 3 metres thick. Son Nghiem of the Jet Propulsion Laboratory in Pasadena, California, and his colleagues used NASA's QSCAT satellite to measure the changes in Arctic perennial ice from 2004 to 2005, by comparing ice cover averaged over November and December in each year, the team reports in Geophysical Research Letters (vol 33, p L17501).

They found that perennial ice cover decreased by 720,000 square kilometres - a 14 per cent drop in one year. This is a dramatic change compared with the 7.8 per cent reduction per decade that has been recorded since the 1970s.

The changes were not evenly spread. Perennial ice made some gains in the west Arctic Ocean, but nearly half was lost in the east. If the trend continues, it could open a vast ice-free region in the east Arctic Ocean, the team says.

From issue 2570 of New Scientist magazine, 23 September 2006, page 5

A good night's sleep is known to improve people's ability to learn actions such as mirror writing. REM sleep, when most dreaming occurs, is thought to be particularly important.

The role of sleep in factual learning has been less clear. Now Matthew Tucker at The City University of New York and his colleagues have shown that even a nap with no REM sleep can help.

Volunteers were told to memorise pairs of words (a test of factual learning) and to practise tracing images in a mirror (action learning). When they were tested straight afterwards and 6 hours later, those who had been allowed a nap of up to 1 hour before the re-test scored 15 per cent better in the factual test than the non-nappers, but no better in the action test (Neurobiology of Learning and Memory, vol 86, p 241).

"Traditionally, time devoted to daytime napping has been considered counterproductive," the researchers say. It now seems sleep is "an important mechanism for memory formation".

From issue 2570 of New Scientist magazine, 23 September 2006, page 17

The findings highlight the challenges facing environmental regulators as they attempt to police the eradication of harmful chemicals from electronic goods. Failure by the regulators might not only put users at risk, but also mean chemicals might leach into groundwater beneath landfills, or contaminate people working in recycling plants where these machines end their lives.

Greenpeace found the toxic chemicals after analysing just a handful of the many hundreds of components inside each computer. Zeina Al-Hajj of Greenpeace says that the discovery of suspect chemicals in such a limited analysis of electronic goods reveals the magnitude of the task facing regulators as they work to enforce new rules on the use of many chemicals in goods, such as the European Union's Restriction on Hazardous Substances (RoHS) directive.

The laptop analysis was carried out at the Eurofins environmental testing lab in Galten, Denmark, and a Greenpeace lab at the University of Exeter, UK. The labs bought five new laptops made by Acer, Apple, Dell, Hewlett-Packard and Sony in March this year. The computers were then dismantled and analysed using various techniques, including X-ray spectroscopy to detect and quantify the presence of certain chemical elements in 40 components, including cooling fans, taken from each computer.

A selection of these samples were then submitted to combined gas chromatography and mass spectrometry to detect the presence of specific compounds. The analysts found that among the five computers, the Hewlett-Packard laptop had some of the highest levels (see Table) of a number of chemicals, including a substance called decabromodiphenyl ether (decaBDE), a flame retardant that the company claims to have removed from its product line some years ago.

Greenpeace stresses that its analysis is not a reflection on any of the manufacturers' entire product lines - and none of them has broken any law. However, the findings are at odds with information about Hewlett-Packard products that the company has placed on its website, which states: "HP eliminated the use of decaBDE many years ago and has no plans to reinitiate its use."

"That is quite shocking," says Jim Puckett of the UN's Basel Action Network in Seattle, Washington. The network monitors breaches of the Basel convention, which regulates the flow of hazardous waste from industrialised countries to developing nations. With the wide range of substitute chemicals available today, there ought to be alternative choices for manufacturers, he says.

"It's disappointing to see these results," says Zoe McMahon, HP's environmental manager for Europe. The company has not been deliberately misleading its customers, she says, and is taking the matter seriously. "Our policy hasn't changed. Several years ago we restricted a number of flame retardants," she says, including decaBDE. It's too early to say how this substance came to escape HP's testing procedures and end up in the laptop that was analysed but HP is working with its suppliers to investigate Greenpeace's findings, she says.

Apple Computer's MacBook laptop analysed by Greenpeace also contained a permitted flame-retardant, called TBBPA, at levels higher than in any of the other computers, says Kevin Brigden at the Greenpeace lab, who oversaw the testing. Apple Computer chose not to respond to Greenpeace's findings when asked for comment by New Scientist.

TBBPA, decaBDE and other brominated flame retardants (BFRs) were once used in many plastic components in electronic goods, but are now being phased out following concerns over their impact on human health and the environment. "Some BFRs persist in the environment and are able to bio-accumulate," Brigden says. Long-term exposure can interfere with brain development, or the endocrine system. One of the problems with these chemicals is that it is difficult to dispose of them through incineration without releasing highly toxic dioxins into the environment. Only the Sony laptop contained no BFRs (see Table).

Controversially, decaBDE is still permitted under the European Union's RoHS directive. It was originally banned but was reinstated after the makers objected to the EU, saying it was less hazardous than other BDEs. However, since commercial decaBDE contains about 3 per cent nonaBDE, which was banned when RoHS came into force on 1 July, the use of decaBDE will now in practice no longer be possible. None of the machines Greenpeace tested was breaking any law, however, because they were purchased in Europe before 1 July.

RoHS may be a European law, but its influence is being felt around the world. Even in the US, where (except in a few states) BFRs are not banned or regulated, the chemicals banned under RoHS are being phased out, Al-Hajj says.

Up to 50 million tonnes of waste electronic equipment is being dumped every year, so residual toxic chemicals are one of the fastest-growing environmental problems, says Michael Williams of the UN Environment Programme. Even with many such substances now banned, the problem of dealing with millions of tonnes of older equipment will remain.

Greenpeace wants all toxic chemicals removed from e-goods. Peter Guthrie at the Centre for Sustainable Development in Cambridge, UK, says that for this to happen it will be crucial to ensure that manufacturers have to take back their products at the end of their lives. Only then will they be more inclined to switch to safer new materials.

From issue 2570 of New Scientist magazine, 25 September 2006, page 26-27

The greener alternatives

For many of the harmful chemicals traditionally used in electronic equipment, there are now a number of safer alternatives, though as Greenpeace found, they are not used as often as they could be.

POLYVINYL CHLORIDE

PVC, a chlorinated plastic, was once used for insulating wiring. But both production of PVC and its eventual disposal can create persistent and highly toxic dioxins, which pose a major health hazard. Alternatives for PVC vary widely depending upon application, but a variety of non-chlorinated alkene-based plastics, such as polyethylene, can replace it in wiring insulation.

LEAD

Solder used to contain as much as 50 per cent lead, but lead-free solder made up of tin, silver, copper, bismuth and zinc is now widely available. These metals' toxicity and ability to accumulate in the body are far lower than for lead, whose highly toxic effects are the same regardless of whether it is inhaled or ingested. These include irreversible tissue damage, particularly to the developing brain and central nervous system, the kidneys and the reproductive system.

BROMINATED FLAME RETARDANTS

Incorporating BFRs into plastic components is intended to enhance safety by making the material less flammable, but BFRs are now known to be a health risk. They accumulate in biological tissue and have been found in human breast milk, too. Chronic exposure interferes with brain and skeletal development. Animal experiments suggest that this may lead to permanent neurological damage, impairing learning and memory. Other studies have shown that some BFRs can act as endocrine disruptors. The three main classes are polybrominated diphenyl ethers (PBDEs), hexabromo-cyclododecane (HBDC) and brominated bisphenols, in particular tetrabromo-bisphenol-A (TBBPA). Alternatives for BFRs include non-toxic silicone-based flame retardants, for instance, which are recyclable many times over.

HEXAVALENT CHROMIUM

Also known as chromium (vi) or chromate, hexavalent chromium is used in electronics as a corrosion inhibitor. It is highly toxic and a known carcinogen. Replacements include the metal's far less reactive trivalent form or nickel-iron-cobalt alloys.

There were no immediate reports of injuries or damage. Roy Allison, director of emergency management for Marlboro County, said he and other residents were woken up by their shaking houses.

At a furniture and appliance store in Wallace, about 10 miles north of the epicenter, "the windows sounded like they were about to bust out," said Valerie Perhealth, daughter of the store's owner. "It scared me so bad."

A magnitude 3.5 quake shook the area Friday. The centers of the two quakes were about 10 miles apart.

Jessica Sigala, a geophysicist with the earthquake center, said the area gets small earthquakes now and then because of faults connected to the Appalachians.

"There's no fear of a bigger earthquake. These (small tremors) just happen," Sigala said.

There were no reports of damage from Friday's quake but there were reports of windows cracking and dishes rattling.

South Carolina each year has, on average, 10 to 15 earthquakes that register below magnitude 3. An earthquake between 3 and 4 normally is recorded about once every 18 months.

The area's most devastating quake on record was a magnitude 7.3 that rumbled near Charleston on Aug. 31, 1886, killing more than 100 people.

The researchers noted that a report in the journal Nature found that 1,700 plant, animal and insect species moved poleward at an average rate of about 4 miles per decade in the last half of the 20th century.

The warming has been stronger in the far north, where melting ice and snow expose darker land and rocks beneath allowing more warmth from the sun to be absorbed, and more over land than water.

Water changes temperature more slowly than land because of its great capacity to hold heat, but the researchers noted that the warming has been marked in the Indian and western Pacific Oceans. Those oceans have a major effect on climate and warming that could lead to more El Nino episodes affecting the weather.

"This evidence implies that we are getting close to dangerous levels of human-made pollution," Hansen said in a statement.

Few scientists doubt that the planet has warmed, though some question the causes of the change.

Hansen, who first warned of the danger of climate change decades ago, said that human-made greenhouse gases have become the dominant climate change factor.

The study said the recent warming has brought global temperature to a level within about one degree Celsius - 1.8 degree Fahrenheit - of the maximum temperature of the past million years.

"If further global warming reaches 2 or 3 degrees Celsius, we will likely see changes that make Earth a different planet than the one we know. The last time it was that warm was in the middle Pliocene, about 3 million years ago, when sea level was estimated to have been about 25 meters (80 feet) higher than today," Hansen said.

The scientists scanned the picture on both sides to obtain high resolution 3D image data of the whole painting which the NRC says will shed new light on the history and condition of the work, as well as on Leonardo da Vinci's technique.

The portrait itself will remain in the Louvre museum in Paris, where it has gazed inscrutably out at visitors since it was moved there after the French Revolution.

But the NRC, which will unveil its findings on Tuesday ahead of a public lecture in Ottawa, promises its model will allow both art history specialists and the general public to get closer than ever before without risking damage to the picture.

It will also reveal important details about Leonardo's technique, including the so-called "sfumato" method by which he created a delicate hazy effect which contributes much to the painting's general air of remote mystery.

The young woman with the ambiguous half smile has been identified as Lisa Gherardini, wife of a Florentine merchant named Francesco de Giocondo and her portrait has attracted admiration and curiosity since its creation 500 years ago.

Its popular status as Western art's most famous masterpiece was cemented in 1911 when it was stolen from the Louvre, sparking a massive hunt that saw even Pablo Picasso questioned by police before the painting turned up again two years later.

"It's unlikely to stop permanently for a long time," Adriano Mazzini told a press conference in Jakarta. "It's hard to say when the overpressure will have been fully released. It could be one, 10 or 100 years. But to seal it will be very, very difficult." According to Mr Mazzini, unless the flow stops soon, the affected land, which has already starting sinking, could subside significantly. "It will be catastrophic," he said.

The mud started flowing on May 29, a couple of hundred metres from where the gas company PT Lapindo Brantas was drilling an exploratory well nearly two miles deep. It has been gushing up to 50,000 cubic metres a day - or two large bathsfull a second - ever since.

At least four villages will almost certainly have to be destroyed, and two others have been flooded. More than 11,000 people have evacuated their homes.

On September 8, the central government, fearing a political disaster as well as the environmental impact, took command of the operation to stem the flow, control the flood (which now covers about 400 hectares (1,000 acres) and supervise the social programmes for the affected communities. A spokesman for the government team told the Guardian the latest findings were "useful and worrying". He said: "They show we still have a lot of work to do."

Observers said the president, Susilo Bambang Yudhoyono, had been wise to intervene. "This could be the achilles heel of this government," said Dennis Heffernan, a political and business consultant. "Unless more resources are put to work, we're in danger of a catastrophe on the level of the Exxon Valdez."

The Exxon Valdez was an oil tanker that sank in Alaska in 1989, causing widespread environmental devastation.

All the expenses are being borne by Lapindo, which is controlled by the family of Indonesia's senior welfare minister, Aburizal Bakrie. Estimated costs are thought to be well over £70m, while the company's insurance only covered £15m.

Mr Mazzini, whose team has studied mud volcanoes for more than a decade and spent just under a week on site, said it was impossible to say conclusively whether the drilling caused the disaster.

There has been speculation that the disaster was caused by Lapindo failing to use a proper casing during drilling. Mr Mazzini said this was unlikely. "This is a huge case of overpressure," he said. "A casing would not have made any difference, I don't think. But I'm not a drilling expert."

The mudflow is thought to have been caused by one of four possibilities: gas-charged fluids breaching coral mounds on top of the limestone rock; a magmatic reaction generating gas; a new-born mud volcano; or hydrothermal fluids migrating from neighbouring areas.

Federal Murray MP Dr Sharman Stone said she had written to Victorian Premier Steve Bracks calling on him to declare a natural disaster to "open the door to financial assistance for orchardists".

The frost was expected to have destroyed half the region's output of fruit, Dr Stone said.

Farmers alone expected to lose $70 million, with losses multiplied through the picking, packing, canning and transport industries, she said.

"This follows five years of drought, hail last year at Shepparton East, the devastating frost of 2003 and record prices for water," Dr Stone said in a statement.

"If the state declares a natural disaster, they will be able to seek reimbursement for up to 75 per cent of their costs from the Federal Government once their expenditure reaches a certain threshold.

"Unfortunately, the process of natural disaster declaration begins with the State Government.

"They must start to think beyond the Great Divide and assist farmers who, through no fault of their own, are facing another severe downturn."