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NS 2 Nov 2002

Secret gas changes face of urban war

Russia used a "non-lethal" gas to rescue its hostages and more than a hundred innocent civilians died. Yet such weapons are top of many countries'wish lists

DEBORA MACKENZIE

THE rescue of hostages held by terrorists at a theatre in Moscow this week has stunned the world. The Russian authorities saved hundreds of lives by using a poison gas to incapacitate the terrorists before they could detonate their bombs, or even put on their gas masks. But the secret knockout agent also killed at least 115 of the hostages. Despite this tragic death toll such weapons appear to be here to stay. Unfettered by international conventions that bar the use of toxic chemicals in war, governments around the world have decided that knockout agents are a powerful tool for fighting the war on terrorism. Drugs that confuse, repel or sedate people are being weaponised by military researchers for rescuing hostages, riot control or urban warfare. The US may even have begun human trials.

This week's rescue demonstrates why many anti- terrorism experts believe these weapons are needed. But, it also reveals that so-called "non-lethal" weapons can be anything but. To the Russian officials dealing with the hostage crisis, the disabling gas must have seemed a godsend. Security forces released it into the theatre to render the terrorists inside unconscious, or at least unable to shoot accurately or detonate their explosives. To that extent it worked and perhaps any other strategy could have resulted in even more deaths. Whatever knockout gas was used, it is often true that the more powerful the drug, the narrower the margin between an effective dose and a lethal one. It takes a hugely powerful drug to knock out a person within seconds. And administering enough to fill a large auditorium inevitably means more sensitive bystanders, or those caught in a concentrated pocket of gas, could receive a fatal dose.

"Drugs that confuse or sedate people are being weaponised for rescuing hostages, riot control or urban warfare"

But many disturbing questions surround the rescue. One is the official secrecy about the gas. Russian military authorities refused to identify it after the attack, even to doctors treating survivors. Officials insisted this could give future enemies an advantage. Yet that knowledge could have saved lives. Such secretiveness pervades research into non-lethals. Since iggg, the US has spent more than $loo million on weapons designed to "incapacitate individuals, deny areas to personnel, and clear structures". Yet the US Department of Defense refuses to publish many reports on what has been done.

"Official secrecy could allow countries to develop devastating chemical weapons without breaking international law"

The secrecy is not because these weapons necessarily violate any treaties. The Chemical Weapons Convention permits virtually any chemical for law enforcement, apart from those such as sarin or VX, which can only be used as weapons and are banned completely. Possibly it stems from fears of a public backlash against the research. Yet, the danger is that without proper scientific testing and more open scrutiny, the risks of such weapons may never be fully appreciated, as seems to have happened in Moscow. There may be more such tragedies. Two years ago, the commander of the US non-lethals programme said that he "would like a magic dust that would put everyone in a building to sleep" (New Scientist, 16 December 2000, P 4). One possible candidate is an aerosolised form of the sedative Valium. But as with the Russian agent, there could be a dangerously narrow margin between an effective dose of Valium and a lethal one. In September this year, documents obtained by the Sunshine Project, a group campaigning against chemical weapons, revealed plans by the University of Pennsylvania to assess the anti-personnel capabilities of an 81-millimetre non-lethal mortar round that has already been subjected to "human effects testing". But the military refuses to divulge any further details. Many experts fear that official secrecy, coupled with a regulatory vacuum and an increasing emphasis on righting terrorism, could allow countries to develop devastating chemical weapons without breaking intemational law. "I fear that countries are developing new types of less- than-lethal agents," says jean- Pascal Zanders of the Stockholm Intemational Peace Research Institute. "This could undermine the core purpose of the chemical weapons treaty, to completely eliminate chemical weapons for the sake of mankind." Yet without some oversight, the possibilities for [email protected] could reach far beyond the rescue of hostages. Donald Watenpaugh of the University of North Texas in Denton told a high-level conference last November that putting long-lasting "anti- aggression chemicals" in the water might be the ultimate solution for regions plagued by war. But he admitted: "Misuse of anti-aggression technology to control civilian populations constitutes a frightening potential problem with this idea." Despite such risks, increasing antipathy to arms control means these weapons are unlikely to be banned by any forthcoming treaties. The secretive weapons programmes appear to be here to stay.

Popular herbicide may gender bend.wild frogs

A FIGHT over frogs could sway the fate of one of the world's most widely used herbicides. A team of toxicologists is claiming that the chemical atrazine is emasculating wild frogs across the US, increasing fears that it could be contributing to amphibians' decline worldwide. But another team of researchers, funded by one of the herbicide's makers, is disputing the team's earlier findings. Atrazine accounts for 40 per cent cyf all herbicide applied in the US, and is sprayed over three-quarters of the country's corn crop. Despite this, the Envimnmental Protection Agency (EPA) is considering whether to restrict the chemical's use. Endocrinologist Tyrone Hayes cyf the University of California, Berkeley, first wamed of the dangers af atrazine earlier this year. Hayes's team found that male ftgs are feminised by a dose cyf atrazine that is just 1130th the EPA safb drinking water standard. Affected males gmw ovaries and muftiple testes and have shrunken voice boxes. But critics charged the work was limited, as ftgs used were an African species (Xenopus laevis) specially bred fbr the lab. Now Hayes's group has gathered data on wild ftgs native to the US that suggest atrazine is every bit as nasty as the Xenopus study hinted, and may indeed be afrecting marrjf amphibian species worldwide. In papers in Mature (vol 419, p 895) and Environmental Health Perspectives (DOI:10.1289/ehp.5932), the team reports that atrazine damages gonads and makes male northern leopard frogs (Rana pipiens) hermaphrodites. In lab tests, the gonadal problems were actually worse at ultra-low doses than at higher ones, perhaps because the endocrine system is attuned to minute concentrations of chemicals that mimic hormones. Hayes's team also correlated the abnormalities in leopard frogs with atrazine concentrations along a 2200- kilomL-tre transect across the US agricultural heartland. The frogs commonly breed in ditches and pools ne)d to corn fields during the peak season for pesticide application. But a panel of academic scientists funded by Syngenta, one (Yf the companies that makes atrazine, questions the result. The panel will present talks at next month's environmental to)dcology conference in Utah that challenge the notion that atrazine harms amphibians. A study led by panel member James Caff of Texas Tech University in Lubbock, to be published in Envifvnmental Toxicology and Chemistry in Ja n ua ry, finds no effect on Xenopusvoice-box muscles and no low-dose effect on gonads. Some biologists suspect industry pressure, but Carr defends the work, and points out that it doesn't let atrazine off the hook completely. "We're not saying atrazine does not cause gonadal abnormalities; our data shows it does," Caff says. Just at concentrations 250 times higher than Hayes found. The EPA is reviewing the risks posed by atrazine, but such FL-Aews often take years. If Hayes is rigttt, and effects Gccur at doses tGo low to regulate, then only an outright ban will be efrecdve. And if a ban is impGsed in the US, the EPA would simply be following marry European countries, which outlawed the chemical years ago. Jay Withgott

NS 10 Aug 2002

The contraceptive plague

Australia has genetically engineered viruses thatcould provide a humane way to controlalien pests such as rabbits. Now itmust decide if it's safe to release them

GRAEME O'NEILL, MILDURA

AFFER more than a decade of trying, Australian researchers have created a highly infectious virus that could wipe out the country's rabbit pests by making them sterile. The team, at the Pest Animal Control Cooperative Research Centr ' e (PAC CRC) in Canberra, has already applied for permission to carry out field trials with a similar virus that makes European mice infertile. Advocates of this form of biological control say it is more humane than existing strategies such as poisoning, shooting or spreading lethal diseases. From cats to camels, feral mammals cost Australia hundreds of millions of dollars each year in lost agricultural production and environmental damage, and have driven some native mammals and birds to extinction. "Australia has lost more mammal species than the rest of the world combined in the past 400 years," says project director Tony Peacock. But the prospect of genetically engineered viruses being released into the wild is still likely to spark a fierce debate. The viruses make females infertile because they have an added gene for a protein from the zona pellucida, the thick layer surrounding the egg. Females infected with one of the transgenic viruses produce antibodies against their own eggs, damaging them and blocking fertilisation - a process called immunocontraception. For rabbits, geneticists chose to engineer the myxoma virus, which devastated populations when it was released in Australia half century ago. But many rabbits have become resistant, and less lethal strains have edged out the original virus. Four years ago, researchers selected the rabbit ZPB gene as the most promising of three zona pellucida genes to insert into the myxoma virus. But this sterilised less than 25 per cent of rabbits. Now they have switched to the ZPC gene, with much better results. In two trials in May, New Scientist has leamed, the latest transgenic myxoma virus sterilised 8 out of 11 female domestic rabbits, while a ninth carried only a single embryo - a success rate of over 7o per cent. It's a highly infectious but non-lethal strain that should give nwa rabbits no more than a fever for a few days. Peacock says if the virus could sterilise 70 to 8o per cent of wfld females, rabbits would decline to densities similar to those in Europe and become a relatively pest But even if it were only 5o per cent successftil, it would still end the episodic plagues that have ravaged the country. The immunocontraception idea has already been proved in another major pest, the European house mouse (New ScientiSt, 26 April 1997, p 4). An engineered herpes virus, murine cytomegalovirus, has consistently produced ioo per cent sterilisation of female mice in lab trials. The PAC CRC w!U apply to the Office of the Gene Technology Regulator 14ter this year for permission to conduct the first contained field trial of the transgenic mouse virus at Walpeup, in north-western Victoria. Peacock says extensive consultation would precede any release. The virus appears to sterilise female mice for life, but it is too early to know if the same will be true with rabbits, which are longer lived. So the team plans to add other genes to the myxoma virus to try to boost the contraceptive effect. If the government decides to release such viruses, Peacock thinks populations should decline rapidly as breeding slows and natural mortality and predation take their toll. Other researchers think the effects will only be temporary, as natural selection will favour animals with a mutated zona pellucida protein that evades the immune response. But Peacock points out that sperm can only fertilise eggs if the proteins on their head bind to the ZP proteins. So for resistance to appear, both egg and sperm proteins would have to mutate simultaneously yet still be able to bind to each other, which is extremely unlikely. However, the viruses could be accidentally - or deliberately - transferred to another continent. Another worry is that the viruses could spread to other species, but the modified viruses are no more likely to jump the species barrier than wild strains. And the myxoma virus has not done this in the 50 years it's been in the country. For Australia's worst feral predator, the fox, the PAC CRC team has not been able to identify a virus that doesn't also infect domestic and wild dogs, including dingoes. So the plan is to modify a canine herpes virus so it can only replicate when an antibiotic such as tetracyline is present. The virus and antibiotic would be added to baits that are irresistible to foxes, but are shunned by dogs and dingoes. Because the virus doesn't infect any native mammals, they would be safe even if they ate the baits. The PAC CRC is also working with a New Zealand research team to develop an immunocontraceptive virus for New Zealand's worst feral predator, the stoat, which also inflicts a heavy toll in Hawaii.

Clue to how power lines could increase the risk of cancer

WEAK magnetic fields from electric appliances or power lines might cause cancer by interfering with the checks cells make before dividing. The finding could explain the limited evidence fbr a link between pylons and childhood leukaemia, but ncyt everyone is convinced. The US National Institute of -Environmental Health Sciences lists low-frequency magnetic fields as a "possible human carcinogen". This circumspect classification reflects the weakness of e%(idence crf arry link. Some population studies have found leukaemia clusters around power lines (NewScientist, 9 August 1997, p 16), but the effect has proved impossible to replicate in the lab. Also, there is no obvious mechanism by which these flelds could cause permanent damage to DNA. Low-energy, low-frequency flelds only induce a small electrical current in body tissues. Now Brian Heaton's work at the University of Aberdeen suggests that these magnetic flelds make cells more slapdash when they are dividing. His team bombarded cell cultures with gamma radiation and then exposed some to a low-frequency magnetic field. Normally, cells stressed with gamma radiation delay division while they repairthe damage, but to the team's surprise, those subjected to the magnetic field didn't pause. In fact, 12 out of 20 cultures exposed to the field actually divided faster than those exposed to radiation alone they report in Cancer Cell lntemationafs online edition. Heaton thinks magnetic fields interfere with the repair processes that normally delay division. So exposure may increase the chances of cancer even though the fields aren't directly damaging DNA. But Michael Rapacholi, a World Health Organization expert on the effects of electromagnetic fields on health, is sceptical. "The effect is too small to be very convincing, 11 he says. He also points out that the magnetic field was a thousand times strongerthan that from a power line. James Randerson

Fresh fears over mobile phones Wednesday, 19 June, 2002, 17:32 GMT 18:32 UK The scientists said mobile phones were still safe to use A major study into the safety of mobile phones has concluded that they may affect the health of people who use them.

Research carried out by scientists in Finland suggests radiation from mobile phones causes changes in the brain.

It is the first time that scientists have looked at the effects of mobile phone radiation on human cells rather than those of rats.

The two-year study concluded that even low-level emissions from handsets are damaging.

Scientists from the Radiation and Nuclear Safety Authority found that exposing human cells to mobile phone radiation damaged the blood-brain barrier - a safety barrier in the body that stops harmful substances in blood from entering the brain.

They discovered that the exposure caused the cells in blood vessel walls to shrink which enabled molecules to pass into brain tissue.

Lab tests

Professor Darius Leszcynski, who carried out the study, said the results came from laboratory tests on human cells and that further research was needed to see if the same effect actually happened in humans.

But speaking to BBC News Online, he said: "The blood-brain barrier has been shown to be affected by radiation in animal studies.

"There is a lot of uncertainty about whether this happens in humans. We have shown some biological effects."

Prof Leszcynski said these changes could have a serious impact on a person's health if they were found to happen in humans.

"If it did happen it could lead to disturbances, such as headaches, feeling tired or problems with sleeping. A study by a Swedish research group even suggested it could lead to Alzheimer's disease."

However, he added: "It is important to remember that our study has been done in the laboratory where we can detect even the smallest changes.

"We cannot say whether it happens in humans. We need further study looking at real people to see if the blood-brain barrier is affected.

"What is happening in the human brain is an absolute enigma. We don't know at all."

'Still safe'

Prof Leszcynski said mobile phones were still safe to use.

"At the moment, there is no scientific support for introducing any sort of limitation either on use of mobile phones or setting new safety limits.

"There is no need because we don't have any science to support it. All the guidelines in place at the moment are fine."

Prof Leszcynski will present his findings at a conference in Quebec, Canada, next week.

He said a study by French scientists, which will also be presented at the conference, found similar results in rats.

Dr Michael Clark, science spokesman at the National Radiological Protection Board, said the research did not show any impact on people's health.

"This is demonstrating a biological effect in cells in the lab."

Speaking to the BBC, he said: "It doesn't relate to a health effect. You can't go from a biological effect in a Petri dish to say that's a health effect."

He added: "The authors themselves are saying that this doesn't mean that mobile phones are unsafe or the guidelines are wrong."

The Consumers' Association said there was still insufficient evidence to say whether or not mobile phones were safe.

A spokesman said: "At the moment, it's too soon to reach a definitive verdict on health risks from mobile phones, but neither has research given it the all clear."

The National Consumers' Council said mobile phone users were reaching their own conclusions about the risks.

"The people who feel that mobile phones are very important and essential in their lives would attach less weight to this new information than those who are already concerned about the risk," said a spokeswoman.

More than 40 million people in Britain have mobile phones, many of them children.

Government studies

Two years ago a government inquiry led by Sir William Stewart concluded that mobile phones posed no provable health risk.

But its report urged caution over the use of mobile phones by children until more was known about their impact on health.

In January, a new £7.4 million research programme was announced, backed by the government and the mobile phone industry, to be managed by an international committee of experts led by Sir William.

The programme includes 15 studies which will seek clear conclusions about the health hazards of mobile phones, in particular fears of an association between mobile phone radiation and brain cancer.

The main purpose of the research will be to see whether "subtle biological changes" already known to be caused by mobile phones pose a risk.

US rejection of nuclear test treaty 'unjustified'

THE US Senate was not justified in rejecting the Comprehensive Nuclear Test Ban Treaty in iggg, according to the US National Academy of Sciences, which has analysed the reasons the Senate cited for the rejection. The treaty bans all tests of nuclear explosives, but opponents in the US government claimed it would prevent the country from safely maintaining fts nuclear stockpile. They also said it would be impossible to monitor compliance, and that cheating would endanger US security. But a study published last week by the NAS refutes all three objections, and concludes that the US would be safer with the treaty than without. Critics of the treaty have long complained that it would be impossible to detect covert explosions. But the panel behind the report, headed by Harvard professor of environmental policy John Holdren, says that any tests small enough to slip under the detection threshold would be of little use to a country that didn't already have nuclear weapons. "We judge that an underground nuclear explosion cannot be confidently hidden if its yield is larger than 1 or 2 kilotons," the panel concluded. By contrast, the crude fission weapons that destroyed Hiroshima and Nagasaki yielded io tO 20 kilotons. To hide small explosions, countries would need to conduct their tests in an "insulating" cavity or simultaneously detonate large amounts of conventional explosives nearby. Explosions in water, open air or solid rock would be easier to spot. Countries such as Russia and China might be able to conceal smaller tests, but states lacking nuclear expertise would have a hard time designing low-yield tests or teaming much from them. Worries that US nuclear stockpiles will degrade over time unless tests continue are also unfounded, says the NAS. "The United States has the technical capability to maintain confidence in the safety and reliability of its existing nuclear weapon stockpile" without further nuclear tests, the panel concluded. Most of the hundreds of nuclear tests the US has performed over the years have been part of weapons development or have tested newly produced models. Only two have been to test older, stockpiled weapons. However, the report is unlikely to make a big political impact, because it was commissioned in 2ooo by the previous Democrat administration. The treaty was rejected by a Republican Senate, and although the Senate is now Democrat- controlled, the Republican Bush administration has said it will not submit the treaty to the Senate for ratification. The US has not conducted a test sincel992,andtheBush administration has not announced plans to resume testing. But that could change with pressure to develop new "bunker-busting" nuclear warheads (New Scientist, 7 October 2000, p 6). Verifying any new designs would probably involve nuclear tests. While the report addressed the reasons given by Senate for rejecting the treaty, it did not consider the issues of military strategy or the desire to test new weapons. Jeff Hecht

Future of corals is going down the pan

MARK SCHROPE, MELBOURNE, FLORIDA

HUMAN waste flushed down the toilet is having a worse effect on the aquatic environment than anyone hadthought. Some corals off the coast of Florida, which form the world's third largest barrier reef, are tainted with bacteria and viruses found in human faeces. Researchers also report this week that prescription drugs flushed into waterways can kill or maim the plankton that are a mainstay of freshwater ecosystems. On average, half of the live coral off Florida has disappeared in the past five years. Scientists and politicians have argued vigorously over just who or what is to blame, echoing similar debates elsewhere in the world. Pollution, overfishing and global warming, which can kill the coral's symbiotic algae, have all been implicated.

But some politicians in Florida have refused to accept that sewage has a major impact. For while there is some evidence that human waste can reach coral reefs miles offshore, it is hardly ever detected by water quality tests. So Erin Lipp, a microbiologist at the University of Georgia in Athens, and her team investigated whether any bacteria or viruses in sewage are contaminating the corals. They analysed the layer of mucus that coats the heads of coral polyps on reefs near shore, and found that the mucus on nine of the 15 corals tested at various locations contained faecal bacteria. Viruses contaminated 14 Of the 15 corals (Marine Pollution Bulletin, vol 44, p 666). Although the team did not study the effect of the sewage on the reefs, the results are significant because faecal bacteria have previously been shown to cause at least one disease that can devastate corals in Florida and the Caribbean. Sewage can also provide nutrients to fuel the growth of algae that attack coral. Lipp will now repeat her study on corals further offshore. But she s . ays it's about time Florida faced up to its sewage problem. There are over 24,000 septic tanks and up to lo,ooo illegal cesspools in the Florida Keys alone, she says. Both allow sewage to seep into the ocean, but politicians have been reluctant to accept the damage they are causing to coral reefs because setting up a centralised sewage system would cost millions. Human waste could also be having a dramatic and unexpected impact on freshwater habitats. The rivers and lakes of Europe and the US are being flooded with high concentrations of artificial chemicals from prescription drugs to bug repellents and narcotics.

Most are excreted and then flushed into the water system. New research reported to the Ecological Society of America's national meeting in Tucson, Arizona, this week suggests that these chemicals could be killing zooplankton, the tiny animals that are an integral part of the food chain in ponds and streams. Postgraduate student Colleen Flaherty and ecotoxicologist Stanley Dodson, both at the University of Wisconsin in Madison, studied water fleas, ordaphnia, which feed on algae and are eaten by fish. They found that, individually, low concentrations of a cholesterol- lowering drug or an antidepressant, both of which are known to pollute rivers, had little effect on Daphnia. But when exposed to both, even for a short time, the animals developed deformities and died in much higher numbers than usual.

Secrets of a long life revealed

ROBIN ORWANT

YOU may be able to have your cake and keep eating it to a ripe old age. it's been shown for the first time that the restricted-calorie diets known to extend the lifespans of animals might work for people too - -and you may not need to go hungry to reap the benefits. Putting animals on a near- starvation diet makes them live up to 50 per cent longer than normal. Until now, though, there was no evidence this works for primates, which of course includes us. To find out, a team led by George Roth at the National Institute on Aging in Maryland has been studying rhesus monkeys. It's too early to say if the monkeys on a restricted-calorie diet are living longer, but they show the same metabolic changes as rodents on the diet: lower body temperature, lower levels of insulin in the blood and less age-related decline in levels of a steroid hormone called DHEAS. They wondered if people who happen to have these metabolic markers lived longer. So they analysed the samples and records of men in the Baltimore Longitudinal Study on Aging, a study that has been running since i958 inwhich volunteers undergo a battery of medical tests every two years. For each of the three markers, they split the records into two halves and compared survival rates (Science, VOI 297, p 8ii). They found that men with lower body temperatures, lower insulin levels or higher levels of DHEAS did tend to live longer. Studies directly testing the effects of a low-calorie diet on humans are already under way. If these people show the same metabolic changes, it will be strong evidence that caloric restriction works for humans too. But it might be possible to live long without having to go hungry. The men in the Baltimore study weren't eating low calorie diets weren't eating low-calorie diets - some of them just happened to have the metabolic signs linked to caloric restriction. "They're doing something we don't know about, or they have good genes," says Roth. In fact, other groups think they know the molecular mechanism behind caloric restriction, and are trying to develop drugs that mimic the effect (New Scientist, 8 June, P 7). DHEAS is already sold in health shops, but there is no evidence that taking it makes any difference. .

Top Down Universe

When subatomic particles are in thrall to distant galaxies you know someone has just rewritten all the rules. J R Minkel explores a weird new world

PHYSICISTS are masters at describing the flickering subatomic world, at predicting how particles whizz about and bump into each other. But when they zoom out and consider the Universe as a whole, the laws governing atoms don't quite fit. They have been struggling with this problem for years, assuming that if they got the right theory everything would fall into place, but maybe they are deluding themselves. Perhaps we simply shouldn't expect the laws of the microworld to explain the world on the largest scale. Thomas Banks of Rutgers University and the University of California in Santa Cruz believes that we simply can't build everything from the bottom up; some large-scale aspects of the cosmos may be just as fundamental as the laws that govern particles. Indeed, the action of the cosmos could even change the properties of individual particles: we could be living in a top-down Universe. It's verging on heresy. Throughout the history of physics, large-scale phenomena have always been explained by smaller scale ones. Gases, for example, can be described as swarms of hyperactive atoms; the atoms in their turn as tiny electrons orbiting dense nuclei, which can be broken down into protons, quarks and so on. The end of the process will come when we find the truly elementary particles and learn to describe the forces between them, preferably within a single theoretical framework. The behaviour of particles, matter, galaxies and the whole Universe should ultimately derive from this "theory of everything," the source of all truth. Already, physics has reconciled three of the four forces that push and tug matter. RElectromagnetism and the so-called strong and weak forces that operate inside atomic nuclei can all be described in terms of their constituent particles: the quarks and electrons that make up matter bounce around under the influence of force particles, such as photons and gluons. But gravity is holding out: there is no theory that describes how gravity works on a subatomic scale. Cue the world's smallest string ensemble. According to string theory, you can think of elementary particles as loops wriggling in 10 dimensions, all differentiated by the kind of wriggle. These quantum rubber bands snap and fuse, giving rise to the four forces. One kind of string would show up as a hypothetical particle that carries the force of gravity. Certainly there are still problems: despite progress over the past five years, we still don't know what the basic principles of string theory are. And it's extremely difficult to calculate anything with strings, so the theory is largely untested. But many physicists are confident that it will work out in the end, and string theory, or something very like it, will be installed as the theory of everything. What throws a spanner into the works is the inconvenient lightness of empty space. Quantum mechanics, an essential part of any small-scale physical theory, says that everything fluctuates. And that includes the vacuum. This means that pairs of particles should be popping in and out of existence all the time, filling space with their energy. To distinguish them from the long-lived particles that make up matter, these ephemeral creatures are called virtual particles. At first glance, this predicted vacuum energy isn't at odds with reality. Over the past seven years or so, astronomers have gathered fairly firm evidence that empty space has an energy of its own. By analysing the brightness of supernova explosions, they have found that distant galaxies are receding from one another faster and faster as time goes by. Space itself seems to be accelerating outwards. To explain this behaviour, physicists'first guess is that there must be some kind of invisible but ubiquitous energy permeating space - energy that generates a repulsive kind of gravity, known as the cosmological constant, that pushes the galaxies apart.

There's one snag, though. Use the equations of quantum mechanics to tot up just how much energy there should be, adding in all the contributions from known subatomic particles such as electrons and quarks, and you get a huge figure. The strength of its repulsion should be so great that the Universe would have blown itself to smithereens long ago.

Superpartners Can strings ride to the rescue? For a while it seemed that they might. That's because adding extra kinds of particles to the Universe can actually reduce the energy of the vacuum. Whereas virtual force-carrying particles (bosons) add their mass to the vacuum, virtual matter particles (fermions) subtract some. Change the balance between bosons and fermions and you could change the energy of the vacuum. Now, strings can vibrate in many different ways - more than enough to account for all the known subatomic particles.

"The most shocking aspect of Banks's idea is that the shape and size of the cosmos can affect physics on a local scale. There have been hints in modern physicsthatthe small and large are intimately connected, butthis pushes the idea to extremes'

So in string theory, there are a lot of extra particles. indeed, every kind of elementary particle could have a long-lost twin, called a superpartner: for every kind of matter particle there'd be a force- carrying twin; for every force particle there'd be a matter twin. Many of these particles, dubbed sparticles, have entertaining names the selectron partners the electron, squarks partner quarks, and the Wino, the superpartner of the W particle which carries the weak force. If the masses of the superpartners were the same as their siblings, though, the vacuum energies of the bosons and fermions would cancel each other out exactly. There would be zero vacuum energy, and zero acceleration. But we already knew that the masses aren't equal: the superpartners must be very much heavier than their ordinary kin, or else we'd have found them in particle accelerator experiments. Given that they have to be so heavy, you can go back and work out a rough figure for the total vacuum energy. And again, it doesn't work out. It's not quite so huge a discrepancy as before, but it's still out by a factor of l0^6O. An embarrassing gap to say the least. This leads many physicists to think that a big conceptual shift is in order. The best ideas they have right now aren't that great: that somehow new physics cancels out all but the barest sliver of vacuum energy; that there are many Universes or patches of this Universe with different random vacuum energies, and we just happen to live in this one; or even that gravity changes at large scales. The particular shift Banks has in mind turns the whole problem on its head. He thinks that maybe string theory can't explain the size of the Universe's acceleration. Indeed, maybe there is no purely bottom-up explanation at all: the acceleration has to be taken as a fact of life. In a sense, it explains itself. Here's how Banks's idea works. In calculating the vacuum energy, the usual assumption is that the number of possible virtual particle states is infinite, so getting the total energy means adding up an infinite series of terms. But according to physicists who study quantum theories of gravity, that may not be so. In quantum gravity, space-time is made of little quantum fluctuations, so the total number of quantum states available is limited. What's more, it's limited in a rather shocking way: instead of growing like the volume of a region, it is proportional to the regions' surface area (New ScientiSt, 27 April, p 22). This "holographic principle" is profoundly counter-intuitive. It means that the bigger the region you are looking at, the more thinly the available quantum states are spread. That makes it rather hard to interpret; how big a region should you look at to calculate your vacuum energy, for example? The bigger the region you choose, the smaller the average vacuum energy you'd get. Unless, that is, there is a meaningful boundary to the Universe. In an accelerating cosmos, the most distant galaxies are hidden from view because light cannot move fast enough to cover the space in between and tell us what's going on out there. There is an absolute limit on all we will ever be able to see. In many ways it is like the event horizon that cloaks a black hole, as nothing from the other side can ever affect us, no matter how far in the future. The horizon in an accelerating space is called the de Sitter horizon, after the Dutch physicist who discovered this space-time as a solution to general relativity. If the horizon defines the limit to what you can ever see, it should also limit the number of quantum states you can observe. And that could reduce the vacuum energy, because the number of virtual-particle states that can exist is also limited by this distant horizon. Andrew Cohen of Boston University and David Kaplan and Ann Nelson of the University of Washington wrote in a 1999 Physical Review Letters paper that this should bring the vacuum energy calculation into line with the acceleration measured by astronomers. Scott Thomas of Stanford University also argues in a paper to be published in PRL that the fewer quantum states in a holographic theory would by themselves tame the cosmological constant problem. But there's no holographic theory that works for de Sitter space yet, so these ideas can't be put on a firm basis. Banks has made a much bolder claim. He says we should just treat the vacuum energy as a measure of the number of quantum states in de Sitter space, and not as something to be calculated from first principles. He hopes that what he'll get is a situation that is self- consistent: the horizon trims the vacuum energy to just the right amount so that it produces the right acceleration to set that horizon. "The cosmological constant determines and is determined by the number of states," says Banks. To some people, this may seem suspiciously circular, or at least hopeful. Banks hasn't won many converts yet. The idea is bold, concedes Leonard Susskind of Stanford University, a string theorist and co-originator of the holographic principle. "But it is very speculative and has not been backed up by any technical calculations.'

Cosmological calcuator

That's not to say that no one is sympathetic. "The idea that the cosmological constant is a measure of the number of states seems quite plausible," says Joseph Polchinski of the University of California in Santa Barbara's Institute for Theoretical Physics. Willy Fischler of the University of Texas in Austin has made that claim too. And indeed, Polchinski's co- worker Raphael Bousso has applied a holographic technique he derived to argue that any universe with a positive cosmological constant must have a finite number of states. The most shocking aspect of Banks's idea is that the shape and size of the cosmos can affect physics on a local scale. There have already been hints in modern physics that the small and large are intimately connected, but this pushes the idea to extremes. Could this radical shift of perspective show us how to fix our fundamental theories? Might string theory emerge stronger than before? As it stands, any quantum field theory, including strings, assumes an infinite number of states. The weird thing, according to Banks, is that physicists haven't found many versions of string theory with broken supersymmetry. In other words', [email protected] theory says that the superpartners ought to be the same mass as their ordinary partners; so a selectron would weigh as much as an electron, and so on. So what breaks this perfect symmetry? Banks thinks it's the de Sitter horizons. The acceleration of the Universe is changing their masses, generating the right vacuum energy. How could the motion of distant galaxies change the properties of a tiny object on Earth? Well, quantum particles aren't just isolated lumps of matter; they come attached to a cloud of virtual particles that trace out every path from the real particle throughout the Universe around it. These branching networks of virtual particles are attached to the real particle at their core, and when you measure the charge or mass of that particle that includes contributions from all the virtual particles too. So the traditional way of calculating the mass of a superpartner means adding up an infWte number of states. But maybe that's wrong. if there's a de Sitter horizon limiting the number of states that any particle can have, then the correct calculation won't have an infinite number of states. The superpartners would be feeling the edge of space and time. Until just recently, Banks had little hard theory to support this idea. But he has now worked out a way that one particular supersymmetric particle, called the gravitino, might become weighed down. The details are highly technical, but the picture is simple enough: first, a virtual gravitino pops into existence near the real gravitino. It zips over to the horizon, buzzes around briefly, then zips back. The number of states it has a chance to interact with in that moment determines the real gravitino's mass, which ends up at around lo-I electronvolts. According to the equations of supersymmetry, this in tum implies that the remaining sparticles are of the order of one trillion electronvolts, just above the capabilities of any existing particle accelerator. The Large Hadron Collides now being built at the CERN laboratory in Geneva, will reach into this range, and could finally detect supersymmetric particles. But to test Banks's theory, we will have to wait for more sophisticated accelerators still to pin down their masses and properties precisely enough to work out whether the theory holds true. If Banks is eventually proved right, then we'll know that the tiniest speck of matter is curiously tied to the fate of the whole Universe. We'll also know that the ultimate quest in physics has hit a rather frustrating brick wall. A theory of (almost) everything, anyone?

JR Minkel is a freelance writer based in New York City

Hex on lucky country

by Greg Andey Austalia correspowent

'CANBERRA - The "Iucky country" is unlikely to be so fortunate in the next 100 years As Australia's big cities sprawl even further and the warming Earth dehydrates resources, hammers health and lashes the continent with a 21st-century equiva- lent of fire and brimstone. Two new studies, on population growth and climate change, predict the nation wig have a harder time preserving its standard of living as plague, pestilence and disaster increasingly become part of life. This means, the federal science agency CSIRO says, that Australia will have to start making decisions now about the kind of life they want their grandchildren to inherit. ACS11RO report to be released in Sydney "tomorrow by Immigration Minister Philip Ruddock says Australia could cope with a population of 50 milhon by the end of the century, although its estimtes are based on an,upper limit of 32 million by 2050. I But even at the lowest projected popula- tion of 20 million, the Australia of two gen- orations hence would face serious challenges - including the management of the potential mega-cities of Sydney and Mel- whose populations could reach 10 million each. Key areas at risk include air quality, stocks of oil and fisheries resources. "We'll have to take a long, hard look at our infrastructure, lifestyle, energy usage, international trade and technology," says researcher Barney For-an, co-author of the CSIRO study. "The real challenge ... is how we reduce the volume of energy and materials we con- sume, while still maintaining our standard of living."

Foran says Australians must recognise that their lifestyles and behaviour wul decide the nation's future, because the long- term consequences to the continents social, economic and environmental systems can be set by short-term choices. And Australia's need to earn more and more foreign exchange to pay for imports and to service international loans will exact a growing toll on the future resources that provide the nation's wealth. CSIRO's message is underlined by another report from Climate Action Net work Australia, focusing on the potential impact of climate change on the nation's health in the coming decades. It projects a general increase of 6C by the end of the centurj, reducing rainfall and promoting wild swings in weather that will batter Australia with more droughts, storms, floods and tropical cyclones. "None of these changes are in doubt, and all of them impact on human health," the report says. "Apart from contributing to Mness and death in Australia through localised air pol- lution, the burning of fossil fuels is bringing a whole new range of risks to the health of the public by creating climate change." The report says all manner of disease - infectious, food, mosquito and waterbome - will be affected by predicted changes m climate, in most cases increasing both deaths and the incidence of potentmry fatal conditions. It is probable, for example, that bacterial diseases in food, such as salmonella will increase, especially in temperate zones. The costs wlU be huge, the report says. Mosquito-home Ross River virus infec- tion already costs Australia up to A$5.7 million a year, and the report says the ease could spread with climate change. This year Tasmania - which was free of the virus until 1994 - reported its first- ever outbreak of Ross River fever. Other likely blows include an increase in waterbome diseases, more frequent algae blooms along the continent's coast- line, and a higher risk of Ciguatera food poisoning from large reef fish and mackerel as the sea warms. The report warns that the incidence of floods, cyclones, dr-ought and bushfires wm increase, and that as the weather becomes hotter and drier, air pollution will become a greater problem. It says that more dust m the air from hotter and drier conditions, for example, clearly contributes to asthma. Fever and related illness could also rise. "The only silver lining in this dark cloud is that there may be a decrease in winter related deaths in Australia," the report says. But it says the extent of the trade-off is not clear, because it is hard to predict whether a fall in deaths from winter respir- atory diseases will outweigh any potential increase in deaths from heat-related stress.