Monday, September 1, 2008

Cosmic crash unmasks dark matter

By Paul Rincon
Science reporter, BBC News

MACS J0025    Image: Nasa, Esa, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University)
Dark matter is shown in blue, ordinary matter is coloured pink

Striking evidence has been found for the enigmatic "stuff" called dark matter which makes up 23% of the Universe, yet is invisible to our eyes.

The results come from astronomical observations of a titanic collision between two clusters of galaxies 5.7 billion light-years away.

Astronomers detected the dark matter because it separated from the normal matter during the cosmic smash-up.

The research team are to publish their findings in the Astrophysical Journal.

They used the Hubble and Chandra space telescopes to study the object MACSJ0025.4-1222 - formed after an incredibly energetic collision between two large galaxy clusters.

Each of these large clusters contains about a quadrillion times the mass of our Sun.

It puts to rest all the worries that the Bullet Cluster was an anomalous case. We have gone out and found another one
Richard Massey, Royal Observatory Edinburgh

A technique known as gravitational lensing was used to map the dark matter with Hubble.

If an observer looks at a distant galaxy and some dark matter lies in between, the light from that galaxy gets distorted.

It looks as if it is being seen through lots of little lenses. And each of these lenses represents a piece of dark matter.

Astronomers used the Chandra X-ray telescope to map ordinary matter in the merging clusters, mostly in the form of hot gas, which glows brightly in X-rays.

As the two clusters that formed MACSJ0025 merged at speeds of millions of kilometres per hour, hot gas in the two clusters collided and slowed down.

However, the dark matter kept on going, passing right through the smash-up.

Speeding bullet

This phenomenon has been seen before, in a structure called the Bullet Cluster - which also formed after the collision of two large galaxy clusters. The Bullet Cluster lies closer to Earth, at a distance of 3.4 billion light-years.

"It puts to rest all the worries that the Bullet Cluster was an anomalous case. We have gone out and found another one," co-author Richard Massey, from the Royal Observatory Edinburgh, told BBC News.

The study sheds light on the properties of dark matter.

The fact that dark matter does not slow down in the collision supports a view that dark matter particles interact with each other only very weakly or not at all (when one excludes their gravitational interaction).

"Dark matter makes up five times more matter in the Universe than ordinary matter," said co-author Marusa Bradac, from the University of California at Santa Barbara (UCSB).

"This study confirms that we are dealing with a very different kind of matter, unlike the matter that we are made of. And we're able to study it in a very powerful collision of two clusters of galaxies."

Larger sample

The latest astronomical observations suggest that dark matter makes up some 23% of the Universe. Ordinary matter - such as the galaxies, gas, stars and planets - makes up just 4%.

The remaining 73% is made up of another mysterious quantity; dark energy, which is responsible for speeding up the expansion of the cosmos.

CMS at Cern (M. Brice/Cern)
The Large Hadron Collider may shed further light on dark matter
According to one model, dark matter may be comprised of exotic sub-atomic "stuff" known as Weakly Interacting Massive Particles (WIMPS).

Others hold that the dark substance consists of everyday matter, rather than some elusive sub-atomic particle. However, this ordinary matter, referred to as Massive Astrophysical Compact Halo Objects (MACHOS), happens to radiate little or no light.

A powerful physics experiment, the Large Hadron Collider, which is currently under construction on the French-Swiss border, could shed further light on this question after it begins operating later this year.

Dr Massey said his team had found other candidates for colliding clusters.

"Ideally, we don't want just one or two, we want lots of these things to really study them statistically," he explained.

"Then we either use the whole lot, or pick out one 'golden bullet' which will provide the best constraints on what dark matter is."

The Hubble Space Telescope failed just after the team had taken their image of MACSJ0025, so they have not yet been able to study these other candidates.

Dr Massey said the astronomers hope to do this after the next Hubble servicing mission with the space shuttle, which is due to launch in October 2008.

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Daydream achiever

By Jonah Lehrer

ON A SUNDAY morning in 1974, Arthur Fry sat in the front pews of a Presbyterian church in north St. Paul, Minn. An engineer at 3M, Fry was also a singer in the church choir. He had gotten into the habit of inserting little scraps of paper into his choir book, so that he could quickly find the right hymns during the service. The problem, however, was that the papers would often fall out, causing Fry to lose his place.

Daydream achiever (David Flaherty for the Boston Globe)

But then, while listening to the Sunday sermon, Fry started to daydream. Instead of focusing on the pastor's words, he began to mull over his bookmark problem. "It was during the sermon," Fry remembers, "that I first thought, 'What I really need is a little bookmark that will stick to the paper but will not tear the paper when I remove it.' " That errant thought - the byproduct of a wandering mind - would later become the yellow Post-it note, one of the most successful office products of all time.

Although there are many anecdotal stories of breakthroughs resulting from daydreams - Einstein, for instance, was notorious for his wandering mind - daydreaming itself is usually cast in a negative light. Children in school are encouraged to stop daydreaming and "focus," and wandering minds are often cited as a leading cause of traffic accidents. In a culture obsessed with efficiency, daydreaming is derided as a lazy habit or a lack of discipline, the kind of thinking we rely on when we don't really want to think. It's a sign of procrastination, not productivity, something to be put away with your flip-flops and hammock as summer draws to a close.

In recent years, however, scientists have begun to see the act of daydreaming very differently. They've demonstrated that daydreaming is a fundamental feature of the human mind - so fundamental, in fact, that it's often referred to as our "default" mode of thought. Many scientists argue that daydreaming is a crucial tool for creativity, a thought process that allows the brain to make new associations and connections. Instead of focusing on our immediate surroundings - such as the message of a church sermon - the daydreaming mind is free to engage in abstract thought and imaginative ramblings. As a result, we're able to imagine things that don't actually exist, like sticky yellow bookmarks.

"If your mind didn't wander, then you'd be largely shackled to whatever you are doing right now," says Jonathan Schooler, a psychologist at the University of California, Santa Barbara. "But instead you can engage in mental time travel and other kinds of simulation. During a daydream, your thoughts are really unbounded."

The ability to think abstractly that flourishes during daydreams also has important social benefits. Mostly, what we daydream about is each other, as the mind retrieves memories, contemplates "what if" scenarios, and thinks about how it should behave in the future. In this sense, the content of daydreams often resembles a soap opera, with people reflecting on social interactions both real and make-believe. We can leave behind the world as it is and start imagining the world as it might be, if only we hadn't lost our temper, or had superpowers, or were sipping a daiquiri on a Caribbean beach. It is this ability to tune out the present moment and contemplate the make-believe that separates the human mind from every other.

"Daydreaming builds on this fundamental capacity people have for being able to project themselves into imaginary situations, like the future," Malia Mason, a neuroscientist at Columbia, says. "Without that skill, we'd be pretty limited creatures."

Teresa Belton, a research associate at East Anglia University in England, first got interested in daydreaming while reading a collection of stories written by children in elementary school. Although Belton encouraged the students to write about whatever they wanted, she was startled by just how uninspired most of the stories were.

"The tales tended to be very tedious and unimaginative," Belton says, "as if the children were stuck with this very restricted way of thinking. Even when they were encouraged to think creatively, they didn't really know how."

After monitoring the daily schedule of the children for several months, Belton came to the conclusion that their lack of imagination was, at least in part, caused by the absence of "empty time," or periods without any activity or sensory stimulation. She noticed that as soon as these children got even a little bit bored, they simply turned on the television: the moving images kept their minds occupied. "It was a very automatic reaction," she says. "Television was what they did when they didn't know what else to do."

The problem with this habit, Belton says, is that it kept the kids from daydreaming. Because the children were rarely bored - at least, when a television was nearby - they never learned how to use their own imagination as a form of entertainment. "The capacity to daydream enables a person to fill empty time with an enjoyable activity that can be carried on anywhere," Belton says. "But that's a skill that requires real practice. Too many kids never get the practice."

While much of the evidence linking daydreaming and creativity remains anecdotal, rooted in the testimony of people like Fry and Einstein, scientists are beginning to find experimental proof of the relationship. In a forthcoming paper, Schooler's lab has shown that people who engage in more daydreaming score higher on experimental measures of creativity, which require people to make a set of unusual connections.

"Daydreams involve a more relaxed style of thinking, with people more willing to contemplate ideas that seem silly or far-fetched," says Belton. While such imaginative thoughts aren't always practical, they are often the wellspring of creative insights, as Schooler's research shows.

However, not all daydreams seem to inspire creativity. In his experiments, Schooler distinguishes between two types of daydreaming. The first type consists of people who notice they are daydreaming only when asked by the researcher. Even though they are told to press a button as soon as they realize their mind has started to wander, these people fail to press the button. The second type, in contrast, occurs when subjects catch themselves daydreaming during the experiment, without needing to be questioned. Schooler and colleagues found that individuals who are unaware of their own daydreaming while it's happening don't seem to exhibit increased creativity.

"The point is that it's not enough to just daydream," Schooler says. "Letting your mind drift off is the easy part. The hard part is maintaining enough awareness so that even when you start to daydream you can interrupt yourself and notice a creative insight."

In other words, the reason Fry is such a good inventor - he has more than twenty patents to his name, in addition to Post-it notes - isn't simply because he's a prolific daydreamer. It's because he's able to pay attention to his daydreams, and to detect those moments when his daydreams lead to a useful idea.

Every time we slip effortlessly into a daydream, a distinct pattern of brain areas is activated, which is known as the default network. Studies show that this network is most engaged when people are performing tasks that require little conscious attention, such as routine driving on the highway or reading a tedious text. Although such mental trances are often seen as a sign of lethargy - we are staring haplessly into space - the cortex is actually very active during this default state, as numerous brain regions interact. Instead of responding to the outside world, the brain starts to contemplate its internal landscape. This is when new and creative connections are made between seemingly unrelated ideas.

"When you don't use a muscle, that muscle really isn't doing much of anything," says Dr. Marcus Raichle, a neurologist and radiologist at Washington University who was one of the first scientists to locate the default network in the brain. "But when your brain is supposedly doing nothing and daydreaming, it's really doing a tremendous amount. We call it the 'resting state,' but the brain isn't resting at all."

Recent research has confirmed the importance of the default network by studying what happens when the network is disrupted. For instance, there is suggestive evidence that people with autism engage in less daydreaming than normal, with a default network that exhibits significantly reduced activity during idle moments. In addition, more abnormal default networks in autistic subjects correlated with the most severe social deficits. One leading theory is that atypical default activity interferes with the sort of meandering memories and social simulations that typically characterize daydreams, causing people with autism to instead fixate on things in their environment.

The exact opposite phenomenon seems to occur in patients with schizophrenia, who exhibit overactive default networks. This might explain the inability of schizophrenics to differentiate properly between reality and the ideas generated by the imagination.

Problems with daydreaming also seem to afflict the aging brain: Harvard researchers recently discovered that one of the main symptoms of getting older is reduced coordination in the default network, as brain areas that normally operate in sync start to fire at different times. Scientists speculate that this deficit contributes to the inability of many elderly subjects to control the duration and timing of their daydreams.

"It's very important to use the default network at the right time," says Jessica Andrews-Hanna, a researcher at Harvard who has studied the network in older subjects. "When you need to focus" - such as during stop-and-go traffic, or when engaged in a conversation - "you don't want to let your mind wander off."

What these studies all demonstrate is that proper daydreaming - the kind of thinking that occurs when the mind is thinking to itself - is a crucial feature of the healthy human brain. It might seem as though our mind is empty, but the mind is never empty: it's always bubbling over with ideas and connections.

One of the simplest ways to foster creativity, then, may be to take daydreams more seriously. Even the mundane daydreams that occur hundreds of times a day are helping us plan for the future, interact with others, and solidify our own sense of self. And when we are stuck on a particularly difficult problem, a good daydream isn't just an escape - it may be the most productive thing we can do.

Jonah Lehrer is an editor at large at Seed magazine and the author of "Proust Was a Neuroscientist." He is a regular contributor to Ideas.

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'Lost World' Beneath Caribbean To Be Explored

Scientists at the National Oceanography Centre, Southampton, are set to explore the world's deepest undersea volcanoes and find out what lives in a 'lost world' five kilometres beneath the Caribbean.

Scientists at the National Oceanography Centre, Southampton, are set to explore the world's deepest undersea volcanoes and find out what lives in a 'lost world' five kilometres beneath the Caribbean.

The team of researchers led by Dr Jon Copley has been awarded £462,000 by the Natural Environment Research Council to explore the Cayman Trough, which lies between Jamaica and the Cayman Islands. This rift in the Caribbean seafloor plunges to a depth of more than 5000 metres below sea level. It contains the world's deepest chain of undersea volcanoes, which have yet to be explored.

The researchers are planning two expeditions over the next three years using the UK's newest research ship, RRS James Cook. From the ship, the team will send the UK's remotely-operated vehicle Isis and a new British robot submarine called Autosub6000 into the abyss.

The team will look for new geological features and new species of marine life in the rift on the seafloor. Geologist Dr Bramley Murton will use a whale-friendly sonar system to map the undersea volcanoes in unprecedented detail to understand their formation. At the same time, oceanographer Dr Kate Stansfield will study the deep ocean currents in the Cayman Trough for the first time and geochemist Dr Doug Connelly will hunt for volcanic vents on the ocean floor. These volcanic vents are home to exotic deep-sea creatures that will be studied by marine biologists Dr Jon Copley and Professor Paul Tyler.

"The Cayman Trough may be a 'lost world' that will give us the missing piece in a global puzzle of deep-sea life," says Dr Copley, a lecturer with the University of Southampton’s School of Ocean and Earth Science. Volcanic vents in the Atlantic are home to swarms of blind shrimp and beds of unusual mussels. But similar deep-sea vents in the eastern Pacific are inhabited by bizarre metre-long tubeworms. The researchers hope to find out whether creatures living in the Cayman Trough are related to those in the Pacific or the Atlantic – or completely different to both.

Before North and South America joined three million years ago, there was a deep water passage from the Pacific to the Atlantic. This means that the undersea volcanoes of the Cayman Trough could harbour a 'missing link' between deep-sea life in the two oceans. Finding out just what lives in the rift will help scientists understand patterns of marine life around the world.

"The deep ocean is the largest ecosystem on our planet, so we need to understand its patterns of life," says Dr Copley. "Deep-sea exploration has also given us new cancer treatments and better fibre-optic cables for the internet, both thanks to deep-sea creatures."

Working at depths of more than five kilometres will take the UK's deep-diving vehicles close to their limits. Isis is the UK’s deepest diving remotely-operated vehicle (ROV) reaching depths of 6,500 metres. The team will control Isis from their research ship to film the ocean floor and collect samples with its robotic arms.

Autosub6000, a new unmanned undersea vehicle built in Southampton, can dive to 6000 metres deep. Autosub6000 is an autonomous underwater vehicle (AUV) – a robot submarine that can carry out missions on its own, without being remote-controlled. The team will launch Autosub6000 from their ship to survey the area and hunt for volcanic vents on the ocean floor.

"These undersea volcanoes lie within British seabed territory recognised by the United Nations," says Dr Copley. "We now have the technology to explore them." The public will be able to follow the progress of the expeditions through web pages updated from the ship. The team will also invite a school teacher to join them and share the scientific adventure with classrooms around the world.

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Stonehenge 'was hidden from lower classes'

Archeologists believe Stonehenge was screened from the view of unworthy Stone Age Britons.
Stonehenge, which today is can be enjoyed by ordinary people and druidic priests alike Photo: Getty Images

The wooden construction extended nearly two miles across Salisbury Plain more than 5,000 years ago, and would have served to shield the sacred site from the prying eyes of ordinary lower-class locals.

Trenches have been dug around the monument, tracing the course of the fence which meanders around the stone circle.

The dig's co-director Dr Josh Pollard, of Bristol University, said: "The construction must have taken a lot of manpower.

"The palisade is an open structure which would not have been defensive and was too high to be practical for controlling livestock.

"It certainly wasn’t for hunting herded animals and so, like everything else in this ceremonial landscape, we have to believe it must have had a religious significance.

"The most plausible explanation is that it was built at huge cost to the community to screen the environs of Stonehenge from view. Basically, we think it was to keep the lower classes from seeing what exactly their rulers and the priestly class were doing."

Mike Pitts, editor of British Archaeology Magazine and author of the book Hengeworld, said: "This is a fantastic insight into what the landscape would have looked like.

"This huge wooden palisade would have snaked across the landscape, blotting out views to Stonehenge from one side.

"The other side was the ceremonial route to the Henge from the River Avon and would have been shielded by the contours.

"The palisade would have heightened the mystery of whatever ceremonies were performed and it would have endowed those who were privy to those secrets with more power and prestige. In modern terms, you had to be invited or have a ticket to get in."

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Google is Now America's Largest Investor In Geothermal Research

Written by Philip Proefrock
Geothermal power is getting a closer look from several directions. These new studies are based on "hot rocks" at temperatures of around 150 degrees C (about 300 degrees F) that can be reached by drilling a couple of miles into the earth's crust. This is a much more involved approach than dealing with surface or near-surface geothermal activity, as is used for much of Iceland's power generation.

Google, which has an interest in affordable power to run its growing numbers of server farms, is heavily investing (through in research into the development of geothermal power. In the US, Google is the largest funding source for geothermal research.

At the same time, the Australian government is investing nearly four times as much as Google to develop geothermal power for Australia. "An Australian Geothermal Energy Association report this week forecast it could potentially produce 2,200 megawatts of baseload power by 2020, adding that represented up to 40 percent of Australia's 2020 renewable energy target."

MIT scientists estimate that the US could develop 100 gigawatts of generating capacity from geothermal over the next 40 years at a cost of US$1 billion. The Australians' timetable is much more aggressive, and comes with a higher price tag. "The association estimated A$12 billion would need to be invested to develop the 2,200 megawatts of power, but added the cost of generating electricity would fall to acceptable levels by the time commercial projects were up and running."

The amount of energy that could be generated from geothermal power is potentially huge. The Australian group estimates that just 1 percent of the country's geothermal capacity could provide 26,000 years worth of clean electricity.

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Lights out? Experts fear fireflies are dwindling

By MICHAEL CASEY, AP Environmental Writer

BAN LOMTUAN, Thailand - Preecha Jiabyu used to take tourists on a rowboat to see the banks of the Mae Klong River aglow with thousands of fireflies.

These days, all he sees are the fluorescent lights of hotels, restaurants and highway overpasses. He says he'd have to row a good two miles to see trees lit up with the magical creatures of his younger days.

"The firefly populations have dropped 70 percent, in the past three years," said Preecha, 58, a former teacher who started providing dozens of row boats to compete with polluting motor boats. "It's sad. They were a symbol of our city."

The fate of the insects drew more than 100 entomologists and biologists to Thailand's northern city of Chiang Mai last week for an international symposium on the "Diversity and Conservation of Fireflies."

They then traveled Friday to Ban Lomtuan, an hour outside of Bangkok, to see the synchronous firefly Pteroptyx malaccae — known for its rapid, pulsating flashing that look like Christmas lights.

Yet another much-loved species imperiled by humankind? The evidence is entirely anecdotal, but there are anecdotes galore.

From backyards in Tennessee to riverbanks in Southeast Asia, researchers said they have seen fireflies — also called glowworms or lightning bugs — dwindling in number.

No single factor is blamed, but researchers in the United States and Europe mostly cite urban sprawl and industrial pollution that destroy insect habitat. The spread of artificial lights also could be a culprit, disrupting the intricate mating behavior that depends on a male winning over a female with its flashing backside.

"It is quite clear they are declining," said Stefan Ineichen, a researcher who studies fireflies in Switzerland and runs a Web site to gather information on firefly sightings.

"When you talk to old people about fireflies, it is always the same," he said. "They saw so many when they were young and now they are lucky now if they see one."

Fredric Vencl, a researcher at Stonybrook University in New York, discovered a new species two years ago only to learn its mountain habitat in Panama was threatened by logging.

Lynn Faust spent a decade researching fireflies on her 40-acre farm in Knoxville, Tenn., but gave up on one species because she stopped seeing them.

"I know of populations that have disappeared on my farm because of development and light pollution," said Faust. "It's these McMansions with their floodlights. One house has 32 lights. Why do you need so many lights?"

But Faust and other experts said they still need scientific data, which has been difficult to come by with so few monitoring programs in place.

There are some 2,000 species and researchers are constantly discovering new ones. Many have never been studied, leaving scientists in the dark about the potential threats and the meaning of their Morse code-like flashes that signal everything from love to danger.

"It is like a mystery insect," said Anchana Thancharoen, who was part of a team that discovered a new species Luciola aquatilis two years ago in Thailand.

The problem is, a nocturnal insect as small as a human fingertip can't be tagged and tracked like bears or even butterflies, and counting is difficult when some females spend most of their time on the ground or don't flash.

And the firefly's adult life span of just one to three weeks makes counting even harder.

European researchers have tried taking a wooden frame and measuring the numbers that appear over a given time. Scientists at the Forest Research Institute Malaysia have been photographing fireflies populations monthly along the Selangor River.

But with little money and manpower to study the problem, experts are turning to volunteers for help. Web sites like the Citizen Science Firefly Survey in Boston, which started this year, encourages enthusiasts to report changes in their neighborhood firefly populations.

"Researchers hope this would allow us to track firefly populations over many years to determine if they are remaining stable or disappearing," said Christopher Cratsley, a firefly expert at Fitchburg State College in Massachusetts who served as a consultant on the site run by the Boston Museum of Science.

Scientists acknowledge the urgency to assess fireflies may not match that of polar bears or Siberian tigers. But they insist fireflies are a "canary in a coal mine" in terms of understanding the health of an ecosystem.

Preecha, the teacher turned boatman, couldn't agree more. He has seen the pristine river of his childhood become polluted and fish populations disappear. Now, he fears the fireflies could be gone within a year.

"I feel like our way of life is being destroyed," Preecha said.

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What do our dreams mean?

What did you dream about last night? Were you chased by some unseen phantom through dark woods; did you get intimate with a Hollywood film star; or were you simply doing some shopping in your local supermarket? According to new research that has analysed more than 22,000 dreams, you're most likely to have dreamt the latter.

The dreams, some dating back to the late 19th century, are stored on the Dreambank at the University of California. The facility, which relies on people phoning the university to report their dreams, is giving researchers new insights into the nature and content of dreams.

The research suggests claims that dreams are top heavy with sex and religion might be wrong, and that most - as many as eight out of ten - are about mundane everyday concerns and interests such as parents, friends, driving, shopping and sport. Men might think about sex every seven seconds, it seems, but don't dream about it anywhere near as much.

Dreams have long been a source of fascination because of their surreal content, our lack of control over them, and the absence of a universally accepted explanation for exactly what they are and whether or not they have any purpose.Although there is no consensus on the purpose, if any, of dreams, there are many theories. One suggests that dreams are random images created by the brain as it reworks the previous day's events, while another proposes that dreaming is simply the brain keeping itself occupied with home-made B movies while the body sleeps.

Yet another theory is that they are part of a survival strategy that evolved in early Man to help him to learn while he slept so he could recognise and deal with threats in a hostile world. Others suggest that dreams have a kind of mulling-over effect, helping to solve problems that cannot be dealt with while awake, or that they are part of the process of memorising the previous day's events, or that they can somehow foretell the future.

Do dreams have a function?

Although there are many of these theories, they broadly split into two camps: those that suggest a function for dreams; and those that propose they have no purpose. “The fact that we remember so few of our dreams, a few per cent at best, argues against any function for dreams. If they are so important, why don't we remember more of them? If dreams are important, why aren't the recallers of them better off in some way?” says Dr Bill Domhoff, of the University of California, Santa Cruz, home of the Dreambank. “We are thinking creatures because thinking is a valuable adaptation, but that doesn't mean that all forms of thinking have a function. Dreams at this moment in the collective findings of dream researchers seem to be a throwaway production, an offhand story to while the night away.''

Dr Domhoff and his colleagues have used new search tools to investigate the content of the individual dreams in the Dreambank, a database whose contributors range from scientists and academics to teenagers, middle-aged women and pensioners. It includes 86 dreams from a physiology graduate student at Massachusetts Institute of Technology that date back to 1897, and 900 dreams from a psychologist recorded between 1913 and 1965. When the psychologists searched the bank for keywords, they found that references to sexual intercourse and religion were relatively rare. Sexual intercourse references were 2 per cent for men and 0.4 per cent for women. Only 3.3 per cent of the dream reports mentioned churches, cathedrals, temples and chapels, and only 0.8 per cent referredto specific religions or denominations.

“The findings from this search raise the general question: why is thinking about sexuality more pervasive in waking thought than it appears to be in dreaming?” say the researchers. “Although dreams and sexuality are often closely related in popular culture, perhaps in part due to Freud's theory concerning the hidden sexual meanings said to be present in most dreams, studies suggest that there is little explicit sexual content in dreams.''

The findings also raise questions about what people dream about. According to the research, as many as 75 to 80 per cent of dreams deal with everyday personal concerns and interests. A dream series from one man that they analysed in detail showed that his mother and father appeared in 23.9 per cent of dream reports, friends in 53.9 per cent, driving 24.5 per cent, outdoor activities 17 per cent, eating 13.7per cent and sport 6.1 per cent.

The theory that dreams are not full of magical worlds and bizarre fantasies but are about events in our day-to-day lives has been bolstered by other research. For example, researchers at the University of Florence found that musicians dream of music more than twice as often as non-musicians. Other research has shown that the number of women dreaming about work has increased at the same time as the proportion of women in the workforce has risen.

An evolutionary purpose

But although the everyday content seems to support the idea that dreams have no function, other researchers have shown otherwise. Researchers at the University of Turku in Finland have found support for an evolutionary purpose of dreams. When they analysed nearly 600 dreams they found that two thirds contained at least one threat, and that more than 60 per cent of these threats were likely to be experienced in real life.

The idea is that during dreaming the brain builds up a model of the world, taking into account what happened in the real world so that strategies can be planned and problems solved.

“The hypothesis is that the biological function of dreaming is to simulate threatening events and to rehearse threat perception and threat avoidance,'' says Dr Antti Revonsuo, a psychologist at the University of Turku. “In the ancestral environment human life was short and full of threats. A dream-production mechanism that tends to select threatening waking events and simulate them over and over again would have been valuable for the development of threat-avoiding skills.'

An aid to daytime learning?

Research at Harvard University has found support for another idea, that sleeping and dreaming boost daytime learning. Researchers found that when they woke people as soon as they had fallen asleep and then analysed the content of their dreams that the subjects were already processing images from a computer game that they had been playing beforehand. That, say the researchers, suggests nocturnal brain processing was helping them to play the game better.

Jim Horne, the director of the Sleep Research Centre at Loughborough University and author of Sleepfaring, is sceptical about the value of analysing the dreams of others. “People who obsessively record their dreams probably are not normal dreamers. Most normal dreamers don't remember dreams because they are junk basically. Most dreams last for 20 minutes or longer, so recall is often of the distorted end of the dream,'' he says.

The idea that dreams have an essential function is further undermined, he adds, by research showing that people taking some drugs, including certain antidepressants, do not dream at all for months. Dreaming, he suggests, is a consequence of the brain not wanting to be switched off for eight hours and its needs to be stimulated. The job of dreams, it seems, may be to keep the brain entertained and the body asleep. “They are the cinema of the mind where the brain creates junk B movies that are entertaining, but which mean little and arebest forgotten.”

Factbox: What do our dreams mean?

The stuff of nightmares

According to the dream specialist Dr Patricia Garfield, a past president of the Association for the Study of Dreams, there are 12 basic nightmares that are universal, including being chased or being naked in public, as well as drowning, falling or being menaced by the dead.

Personality and dreams

People with conservative personalities dream more about being chased, fall from high buildings with greater frequency, and are prone to themes of discontent and unhappiness. They also have far fewer sexual dreams, according to research by the Santa Clara University, California.

Be careful what you read

People who are attracted to fantasy novels are more prone to nightmares, while children who read scary books are three times as likely to have scary dreams, according to research at Swansea University. It also shows that the dreams of those who prefer romantic novels are more emotionally intense.

Flying high

Nearly one person in 12 has had a recent dream about flying, according to a study at Mannheim University in Germany. “The increase in people who report flying dreams might reflect the increasing amount of air travel,'' they say.

Don't watch the news

Dream topics change in response to what we worry about. According to dreams filed at the World Dream Bank, a library of 1,500 dream texts and images (, more people seem to be dreaming about climate change, while a study at Tufts University in Boston disclosed that the dreams of dream diarists immediately after the 9/11 attacks were different from those just before.

Dreams in numbers

5-30 minutes the average length of a dream

Every 90min how often we dream at night

33% of dreams convey misfortune

25% of dreams take place in a known location

50% of social interactions in dreams are aggressive, usually towards the dreamer

95% to 99% the proportion of dreams that we forget

Source: Times database, Sleepfaring by Professor Jim Horne

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Fears over damage to US oil rigs

Oil rig in the Gulf of Mexico
The Gulf of Mexico accounts for a quarter of US oil production

With Hurricane Gustav on course to hit the US Gulf of Mexico coast, the damage it does to the region's oil facilities could be a "worst case scenario".

The stark warning comes from extreme weather impact analyst Jim Roullier, who says Gustav may be more damaging than 2005's Hurricane Katrina.

Output from oil rigs in the US Gulf has already been cut by three-quarters, as staff continue to be evacuated.

The region produces 25% of the US's crude oil and 15% of its natural gas.

About 4,000 offshore oil and gas facilities are located in the US gulf, 100 of which were badly damaged three years ago by Katrina and the follow on Hurricane Rita.

UK oil giants BP and Shell said on Sunday that all of their Gulf of Mexico facilities were being shut down.

"This storm will be more dangerous than Katrina," said Mr Roullier, of Planalytics.

"I think this storm will prove to be a worst case scenario for the production region."

Impact on prices

Forecasters predict that Gustav will hit the central Louisiana coast west of New Orleans by late Monday or early Tuesday.

Predicted route of Hurricane Gustav (31 August 2008)

Concern about the impact of Gustav is likely to push global oil prices higher when trading resumes on Monday.

Crude prices had increased last week as concern mounted about Gustav, before finishing slightly down on Friday.

US light sweet ended Friday 13 cents lower to $115.46 a barrel, while London's Brent closed down 12 cents to $114.05.

However, it is important to remember that global demand for oil has eased since record highs of more than $147 a barrel were hit back in July.

The mayor of New Orleans, Ray Nagin, has already ordered the evacuation of the city.

In 2005, three-quarters of the city was flooded by Katrina after a storm surge breached its protective levees.

More than 1,800 people died in coastal areas.

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Ice Age lesson predicts a faster rise in sea level

Writing this week (Aug. 31) in the journal Nature Geoscience, a team of researchers led by University of Wisconsin-Madison geologist Anders Carlson reports that sea level rise from greenhouse-induced warming of the Greenland ice sheet could be double or triple current estimates over the next century.
"We're not talking about something catastrophic, but we could see a much bigger response in terms of sea level from the Greenland ice sheet over the next 100 years than what is currently predicted," says Carlson, a UW-Madison professor of geology and geophysics. Carlson worked with an international team of researchers, including Allegra LeGrande from the NASA Center for Climate Systems at Columbia University, and colleagues at the Woods Hole Oceanographic Institution, the California Institute of Technology, University of British Columbia and University of New Hampshire.

Scientists have yet to agree on how much melting of the Greenland ice sheet — a terrestrial ice mass encompassing 1.7 million square kilometers — will contribute to changes in sea level. One reason, Carlson explains, is that in recorded history there is no precedent for the influence of climate change on a massive ice sheet.

"We've never seen an ice sheet disappear before, but here we have a record," says Carlson of the new study that combined a powerful computer model with marine and terrestrial records to provide a snapshot of how fast ice sheets can melt and raise sea level in a warmer world.

Carlson and his group were able to draw on the lessons of the disappearance of the Laurentide ice sheet, the last great ice mass to cover much of the northern hemisphere. The Laurentide ice sheet, which encompassed large parts of what are now Canada and the United States, began to melt about 10,000 years ago in response to increased solar radiation in the northern hemisphere due to a cyclic change in the orientation of the Earth's axis. It experienced two rapid pulses of melting — one 9,000 years ago and another 7,600 years ago — that caused global sea level to rise by more than half an inch per year.
Those pulses of melting, according to the new study, occurred when summer air temperatures were similar to what are predicted for Greenland by the end of this century, a finding the suggests estimates of global sea level rise due to a warming world climate may be seriously underestimated.

The most recent estimates of sea level rise due to melting of the Greenland ice sheet by the Intergovernmental Panel on Climate Change (IPCC) suggest a maximum sea level rise during the next 100 years of about 1 to 4 inches. That estimate, Carlson and his colleagues note, is based on limited data, mostly from the last decade, and contrasts sharply with results from computer models of future climate, casting doubt on current estimates of change in sea level due to melting ice sheets.

According to the new study, rising sea levels up to a third of an inch per year or 1 to 2 feet over the course of a century are possible.

Even slight rises in global sea level are problematic as a significant percentage of the world's human population — hundreds of millions of people — lives in areas that can be affected by rising seas.

"For planning purposes, we should see the IPCC projections as conservative," Carlson says. "We think this is a very low estimate of what the Greenland ice sheet will contribute to sea level."

The authors of the new Nature Geoscience report were able to document the retreat of the Laurentide ice sheet and its contributions to changes in sea level by measuring how long rocks once covered by ice have been exposed to cosmic radiation, estimates of ice retreat based on radiocarbon dates from organic material as well as changes in ocean salinity.

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Large Wind Power Park Will Be Peru’s First Major Alternative Energy Project

Arctic becomes an island as ice melts

By Auslan Cramb

The North Pole has become an island for the first time in human history as climate change has made it possible to circumnavigate the Arctic ice cap.

Global warming has caused the Arctic icecap to retreat from neigbouring continents creating opening a gap

The historic development was revealed by satellite images taken last week showing that both the north-west and north-east passages have been opened by melting ice.

Prof Mark Serreze, a sea ice specialist at the National Snow and Ice Data Centre (NSIDC) in the US said the images suggested the Arctic may have entered a "death spiral" caused by global warming.

Shipping companies are already planning to exploit the first simultaneous opening of the routes since the beginning of the last Ice Age 125,000 years ago. The Beluga Group in Germany says it will send the first ship through the north-east passage, around Russia, next year, cutting 4,000 miles off the voyage from Germany to Japan.

Meanwhile, Stephen Harper, Canada's Prime Minister, has announced that ships entering the north-west passage should first report to his government. The routes have previously opened at different times, with the western route opening last year, and the eastern route opening in 2005.

The satellite images gathered by Nasa show that the north-west passage opened last weekend and the final blockage on the east side of the ice cap, an area of sea ice stretching to Siberia, dissolved a few days later.

Last year the extent of sea ice in the Arctic reached a record low that could be surpassed in the next few weeks, with some scientists warning that the ice cap could soon vanish altogether during summer.

Four weeks ago tourists had to be evacuated from a park on Baffin Island because of flooding caused by melting glaciers, and polar bears have been spotted off Alaska trying to swim hundreds of miles to the retreating ice cap.

Measurements on August 26 showed an ice cap of just over two million square miles, confirming the second biggest ice cap melt since records began. New of the opening of the passages emerged as the British explorer and adventurer Lewis Gordon Pugh began a kayak expedition to the North Pole aimed at drawing attention to the dramatic impact of melting polar ice.

"I want to bring home to world leaders, on this expedition, the reality of what is now happening here in the Arctic," said the 38-year-old environmentalist in his blog.

"The rate of change is clearly faster than nearly all the models predict, which has huge implications for climate change and how to tackle it."

Meanwhile Prof James Lovelock, of the University of Oxford, has claimed "planet-scale engineering of the climate" may have to be attempted to counter global warming.

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Eiffel Tower's lights are to go out

By Henry Samuel in Paris

Eiffel tower
The decision is part of a plan to make the Eiffel tower and other monuments more environmentally friendly. Photo: Paul Grover

The French capital's top landmark first donned its "diamond dress" of flash bulbs to mark the new millennium, but they were kept on due to popular demand.

Since January 1, 2000, every hour after dusk, the 20,000 bulbs twinkle brilliantly for ten minutes in what has become a tourist hit.

But starting next month, Sete, the company subcontracted by Paris to run the tower, has decided to half the time the bulbs are on, cutting illumination from 400 to 200 hours per year.

"It's above all a symbolic decision, as the cost savings are not enormous", said the tourism deputy of Paris mayor Bertrand Delanoë.

"But in terms of image, it shows that we are putting sustainable development into practice", Jean-Bertrand Bros told the Journal du Dimanche.

The decision is part of a plan to make the Eiffel tower and other monuments more environmentally friendly. Tickets and documents in the tower are made of recycled paper, and management claims that all the electricity used comes from renewable sources. It is currently studying a plan to put solar panels on the roof of its restaurants.

This latest green initiative comes just after the "city of light" completed a massive five-year energy saving plan to replace the standard incandescent light bulbs with metal iodide light bulbs on 125 of its' monuments.

The new bulbs have five times more energy efficiency and last much longer.

Now, just 218 kilowatts are necessary to power the floodlights on the 280 Paris monuments, down 927 kilowatts from what was needed before to make the city glow. The city's the power bill has been divided by four as a result.

Mr Delanoë, who was re-elected this year for a second term, has put the environment at the heart of his policy-making, introducing a popular low-cost bike rental scheme and reducing traffic volume by 10 percent by multiplying bus lanes, cutting parking spaces, widening pavements and by promoting public transport.

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Hurricane Gustav becoming Category 5 storm

Associated Press

WASHINGTON - Hurricane Gustav is growing into a monster Category 5 storm, the government's disaster relief chief said Saturday. The storm could reach landfall along the Gulf Coast by early Tuesday.

David Paulison, who heads the Federal Emergency Management Agency, told reporters several times at a briefing that the storm was strengthening into a Category 5 hurricane -- a category that means winds greater than 155 mph and a storm surge greater than 18 feet above normal.

FEMA officials said Bill Read, the director of the National Hurricane Center, interrupted an afternoon teleconference involving FEMA, Gulf Coast states and the National Weather Service to say he was going to issue a special advisory statement raising Gustav to Category 5.

"Bill Read got up in the middle of that, interrupted it and said they've just upped the category to a Category 5 storm. That puts a different light on our evacuations and hopefully that will send a very clear message to the people in the Golf Coast to really pay attention," Paulison said.

After Paulison's briefing, hurricane forecasters said the storm still was classified as Category 4 although it was intensifying rapidly. They are predicting it will grow into a Category 5 hurricane by early Sunday.

A FEMA spokesman, Butch Kinerney, also said after the briefing that Read had said he would issue a special advisory statement that would bring Gustav "up to a Category 5 coming off of Cuba," but did not say when that change would happen.

Gustav already has killed 81 people in the Caribbean and it was on a course for the Katrina-battered U.S. coast.

Cuba grounded all national airline fights, though planes bound for international destinations were still taking off at Havana's Jose Marti International Airport. Authorities also canceled all buses and trains to and from the capital, as well as ferry and air service to the Isla de Juventud, the outlying Cuban island-province next in Gustav's path.

Heavy winds had already felled mango and almond trees and were shaking the roofs of buildings in the province, said Ofilia Hernandez, who answered a community telephone near downtown Nueva Gerona, Isla de la Juventud's largest city.

"Everyone's at home. It's getting very ugly," she said. "All night last night there was wind, but not like now. Now it's very strong. Things are starting to fall down."

The government's AIN news agency said officials were evacuating some 190,000 people from low-lying parts of tobacco-rich Pinar del Rio province on the western tip of Cuba's main island. AIN reported that 50,000 already had been evacuated further east.

Stiff winds whipped intermittent rains across Havana, where police officers in blue and orange rain coats supervised workers removing stones, tree branches and other debris from the storied beachfront Malecon, as angry waves crashed against the sea wall below.

Some shuttered stores had hand-scrawled "closed for evacuation" signs plastered to their doors. At others, small lines formed as residents stocked up on bread. Cars waiting to fill up their tanks stretched into the street outside some gas stations.

"It's very big and we've got to get ready for what's coming," said Jesus Hernandez, a 60-year-old retiree who was using an electric drill to reinforce the roof of his rickety front porch.

The U.S. naval base at Guantanamo, Cuba, was hundreds of miles (kilometers) to the east, out of the storm's path.

Gustav rolled over the Cayman Islands Friday with fierce winds that tore down trees and power lines while destroying docks and tossing boats ashore on Little Cayman Island, but there was little major damage and no deaths were reported.

Gustav's eye was centered close to the Isla de Juventud and about 110 miles (180 kilometers) south of Havana. It was expected to be moving northwest near 14 mph (22 kph).

Hurricane force winds extended out 70 miles (110 kilometers) in some places.

Haiti's Interior Ministry on Saturday raised the hurricane death toll there to 66 from 59. Jamaica upped its death toll to seven from four. Gustav also killed eight people in the Dominican Republic.

Gustav could strike the U.S. Gulf coast anywhere from the Florida Panhandle to Texas, but forecasters said there was an increasing chance that New Orleans will get slammed by at least tropical-storm-force winds, three years after devastating Hurricane Katrina.

People began pouring out of the city along the highways and the government announced plans for broader evacuations. The Federal Emergency Management Agency said it expects a "huge number" of Gulf Coast residents will be told to leave the region this weekend.

As much as 80 percent of the Gulf of Mexico's oil and gas production could be shut down as a precaution if Gustav enters as a major storm, weather research firm Planalytics predicted. Oil companies have already evacuated hundreds of workers from offshore platforms.

Retail gas prices rose Friday for the first time in 43 days as analysts warned that a direct hit on Gulf energy infrastructure could send pump prices hurtling toward $5 a gallon. Crude oil prices ended slightly lower in a volatile session as some traders feared supply disruptions and others bet the U.S. government will release supplies from the Strategic Petroleum Reserve.

Meanwhile, the hurricane center said Tropical Storm Hanna was projected to near the Turks and Caicos Islands late Sunday or on Monday, then curl through the Bahamas by early next week before possibly threatening Cuba.

It had sustained winds near 50 mph (85 kph) Saturday and the hurricane center warned that it could kick up dangerous rip currents along parts of the southeastern U.S. coast.

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This place is the bomb

By David Wolman

Christmas Island

Photo by David Wolman

Today, sooty terns swarm over the cracked cement foundations where, 50 years ago, British and U.S. personnel detonated nuclear weapons above Christmas Island.

CHRISTMAS ISLAND -- Driving south on Christmas Island's lone north-south road, Tonga Fou and I are heading to the spot where, 50 years ago, the British military detonated a couple of thermonuclear weapons. Fou, 81, smokes USA Gold Full Flavor 100 cigarettes. As he runs a leathery hand across his forehead, he recalls his experience during one of the test explosions.

Crowded onto a military vessel in case of an emergency evacuation, Fou huddled with his wife and two children. The blast shook the boat, as if it had been shoved by a deity, and everyone winced as their ears popped. About a minute after the detonation, Fou wandered on deck, looked up and thought the world was coming to an end. "It was just terrible," he says. "The mushroom cloud was beginning to come up, with these bright colors, like breaking waves of fire, going up, bigger and bigger, until the sky was all red."

Between 1957 and 1962, this former British colony in the equatorial Pacific played involuntary host to 30 nuclear explosions conducted by the British and U.S. militaries. Code-named Operation Grapple, Britain's tests at Christmas (also known as Kiritimati) and neighboring Malden Island ranged from a 3,000-kiloton explosion 8,200 feet in the air and far out to sea, to a 24-kiloton "balloon-suspended air burst over land." (For comparison, the bomb dropped at Hiroshima had about a 15-kiloton yield.) With thousands of troops, weekly DDT spraying to keep fly populations at bay, and a steady stream of boats and airplanes delivering ever more provisions, it's safe to say that the Cold War's tenure on Christmas Island didn't exactly follow the mindful traveler's dictum: Take only pictures, leave only footprints.

But things change, even in places where WMD have inflicted their catastrophic toll. The Partial Test Ban Treaty, signed in 1963, brought an end to U.S. and British testing in the region. In the '70s, the British government followed up at Christmas with Operation Hard Look, investigating whether radioactive fallout might be found on the island and, if so, determining what to do with it. They didn't find any, although there was no shortage of trash -- abandoned vehicles and drums, mostly, decaying rapidly in the humid climate.

In 1975, American surveyors drew the same conclusion about lingering radioactivity. Still, for goodwill, to avoid future liability, or both, the British recently carried out a cleanup operation on Christmas, carting away tons of decades-old debris, most of which had been concentrated in a junkyard next to the village of Banana and totaled more than 30,000 cubic yards of material. Last May, the final shipment of waste was loaded onto a vessel bound for the U.K.

Fou is the last living person on Christmas Island who was here when the nukes, nuke scientists and soldiers came to town. Now only fragments of that era remain: old truck tires stacked as a makeshift fence between village huts, concrete platforms where buildings once stood, a rotted wooden backboard on a metal pole -- what was once a basketball hoop for recreating servicemen -- and a crumbling church constructed of dead coral and concrete.

What can be found in abundance, however, is nature. In the intervening decades since the era of nuclear-weapons testing, the natural world has quietly rebounded. Today, Christmas Island, Bikini Atoll and other Cold War proving grounds, like Monte Bello north of Perth, Australia, constitute some of the most ecologically intact corners of the world, emitting not radiation but a peculiar allure; it's atomic tourism with a naturalist spin.

Marine biologists diving at Bikini have returned with glowing reports. Inspecting a mile-wide crater left by a hydrogen bomb that exploded with a force 1,000 times greater than the bomb dropped on Hiroshima, researchers recently found the lagoon to be 80 percent covered by thriving corals, with some species growing into huge, treelike formations.

Karen Koltes, a coral specialist with the U.S. Department of the Interior, says reefs around places like Bikini "are among the few examples left in the world of what an ecosystem looks like absent human presence and exploitation." (Unintentionally pouring on the irony, scientists will sometimes employ the word "pristine.") This nature-despite-nukes contrast can be seen at other former test sites, such as the waters surrounding Alaska's Amchitka Island where, 40 years ago, the U.S. conducted three underground explosions. The same is true of the desolate dunes of a former French test site in Algeria, and even the scrublands inside the fence at the Nevada Test Site.

Radioactive materials are long-lasting, which is what makes them both scary and misunderstood. The smoke detectors in your home likely contain a radionuclide called americium. But the reason to worry about them has nothing to do with radioactive material and everything to do with whether the detector's battery is working. Contrary to popular belief, previously bombed geographies are not transformed into lifeless, poisoned landscapes for the next 50,000 years. Hiroshima and Nagasaki look just like every other bustling Japanese city, and crawling around in the grass of a city park there is no different than doing so in Seattle or Milan, Italy, or Auckland, New Zealand, at least as far as radiation hazard is concerned.

But that's not to say everything is peachy with former nuke test sites. Radioactive fallout, and the dizzyingly complex study of it, depends on factors such as microclimates, local geography, wind, altitude of detonation, size of the bomb and environmental conditions on the ground like soils, rock type and vegetation. There are places in the Pacific you don't want to go and probably can't -- that's why they're off limits. The same is true for parts of the Nevada Test Site and other detonation locations.

On or around once-pummeled Pacific Islands, the matter of harmful radiation depends on where you go and whom you ask. Christmas Island, as far as anyone can tell, was always safe from radioactivity, thanks to winds that carried fallout out to sea. And in the ocean -- not just around Christmas but anywhere -- radioactive materials dilute quickly, rendering them essentially harmless. It's when they're concentrated that they can be dangerous.

At places like Bikini and Rongelap Atolls in the Marshall Islands, the picture gets murkier. In the 1950s, the locals on Rongelap watched fallout, delivered on the wind, sprinkle down from above like snow. (And this from a people who had never seen snow.) The islanders were evacuated, only to return and then evacuate again years later because of renewed fears about perceived radiation hazards.

Today, the people of Rongelap are planning to resettle their homeland yet again. The government of the Republic of the Marshall Islands wants the U.S. to cough up money and medical support for cancers caused and damage done during the era of nuclear testing. The U.S. says a previous settlement of $150 million should have done the trick, and this conflict remains a contentious one, at least for the Marshallese. As for existing radiation hazard, U.S. and independent scientists say there is none, although you wouldn't want to dine month after month on certain local plants that accumulate radioactive material.

Still, it's one thing to accept government reports declaring that a place once used for thermonuclear target practice is fallout-free and not hazardous to one's health. It's quite another thing to travel there on vacation.

Geiger counter in hand, I hopped off the skiff and onto the coral beach at the tiny island of Motu Tabu, inside the lagoon at Christmas Island. Rain showers gave way to a mix of billowing clouds and hammering equatorial sunshine. The cacophony from the seabird colony intensified as I approached, but the thousands of noddy and sooty terns did not leave their posts, standing guard over black-speckled eggs. Encountering animals so unaccustomed to human visitors, I thought of Darwin in the Galapagos.

I switched on the Geiger counter and squinted at the digital display. The readings were minuscule -- 0.008, 0.003, 0.006 milli-Roentgens per hour -- numbers indicating nothing more than background radiation from the sun, and noticeably lower than the background radiation levels one would find in a typical American city.

For an unconventional island adventure away from it all, Bikini may have the name recognition, but Christmas is easier for most Americans to get to -- just a three-hour flight from Honolulu. The largest coral atoll on the planet, Christmas is 124 square miles of land, set in the shape of a globular crucifix, with two spits at the northern end enclosing a lagoon. (The island first became known to the Western world when Capt. James Cook discovered it on Christmas Eve, 1777.)

The island is perfectly -- no, ridiculously -- flat. The highest point is a 35-foot-high mound, Joe's Hill, erected by a British serviceman who was bulldozing coral and tar sands to construct the road that runs the length of the island. According to one account, he made the miniature hill as a perch for camping, preferring the seaside solitude to the military barracks. The rest of the island setting is made up of palm trees, a ubiquitous plant called saltbush, inedible crabs skittering everywhere, and sun that will burn you through a T-shirt.

In 1979, the British ceded possession of the island, and Christmas became the easternmost outpost of the scattered island nation of Kiribati. Straddling the international dateline, the country covers an area of the Pacific Ocean equal to that of the continental U.S., even though the tiny islands together total 311 square miles. The island's 5,000 residents subsist on international aid, tropical fish exports and scarce tourist dollars. They live in tiny villages composed of huts and yards patched together with tin, palm-thatched roofs and pigs roaming streets littered with rusting corned beef cans.

The splendor of this place is out on, and in, the water. Fly-fishing enthusiasts who come to Christmas are on a pilgrimage to stalk the elusive, torpedo-fast and deceptively strong bonefish. Christmas is home to the largest bonefishing flats in the world, shallow waters in which the fish feed on tiny shrimp, sometimes revealing their whereabouts by nosing into the sand and extending their sparkling silvery tails above the waterline. When I called one fly-fishing expert who had been to Christmas to ask for a few travel tips, he said, "If you go there without a fishing rod, you should be shot."

Vacationing anglers, decked out in $100 UV-protective shirts, long-billed hats and polarized sunglasses, carrying in their rod setup and tackle cases another $1,500 worth of gear, spend upward of 10 hours a day wading in the calf-deep waters of the lagoon, casting shrimp-shaped flies toward their prey. The visiting sport-fishermen are so essential to the barely extant island economy that locals are, at least on paper, forbidden from eating the bonefish. (Inedible in the eyes of most Westerners, bonefish are part of the islanders' regular menu.)

But some non-fishing-obsessed travelers do manage to make their way to Christmas. One morning, paddling kayaks on the far side of the lagoon, Garry and Kerry Phillips of Brisbane, Australia, were delighted to spend an afternoon in a place where they didn't see another soul for hours -- only manta rays gliding through the shallows. Having traveled and scuba-dived throughout the Pacific and points beyond, they were stunned by the quality of what they saw on the island of nuclear detonations.

"When we were looking into this trip, I did consider the weapons," recalls Garry. "I wondered if it might look like a concrete wasteland or something." But after a week spent kayaking in the aquamarine flats, snorkeling among kaleidoscopic reef fish, and then, at the seabird colony, appreciating the chance to spot rare bird species such as the phoenix petrel and red-footed booby, Phillips laughed at his pre-trip preconceptions. "The contrast of it is amazing. I mean, the hydrogen bomb is the most powerful and destructive thing there is, right? Yet out here, this place, and the reefs we saw yesterday -- it's just gorgeous."

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Plastic Electrical Grid Will Generate Power at Bottom of PA River

How Strong Can a Hurricane Get?

Hurricane Gustav, churning toward the Gulf Coast now, has a small chance of becoming a Category 5 storm before it makes landfall, according to the National Hurricane Center. That would put its winds at 156 mph or stronger. Such winds would devastate most buildings and trees in the storms path. Little would be left standing.

There is no such thing as a Category 6 storm, in part because once winds reach Category 5 status, it doesn't matter what you call it, it's really, really bad.

Category 5 on the Saffir-Simpson hurricane scale has no upper bound, on paper. But in theory, winds from a powerful hurricane could blow the scale out of the water, scientists say.

Pushing the limit

The scale starts with a Category 1, which ranges from 74 to 95 mph. A Category 5 storm has winds of 156 mph or stronger. An extrapolation of the scale suggests that if a Category 6 were created, it would be in the range of 176-196 mph.

Hurricane Wilma, in 2005, had top winds of 175 mph.

How much higher could hurricane winds blow? A hurricane gains strength by using warm water as fuel. With Earth's climate warming, oceans may grow warmer, too. And so, some scientists predict, hurricanes might become stronger.

But physics dictates there must be a limit. Based on ocean and atmospheric conditions on Earth nowadays, the estimated maximum potential for hurricanes is about 190 mph, according to a 1998 calculation by Kerry Emanuel, a climatologist at the Massachusetts Institute of Technology.

This upper limit is not absolute, however. It can change as a result of changes in climate. Scientists predict that as global warming continues, the maximum potential hurricane intensity will go up. They disagree, however, on what the increase will be.

200 mph or more

Emanuel and other scientists have predicted that wind speeds — including maximum wind speeds — should increase about 5 percent for every 1 degree Celsius increase in tropical ocean temperatures.

Chris Landsea, a meteorologist at the National Hurricane Center, disagrees.

After Wilma, Landsea said that even in the worst-case global warming scenarios, where global temperatures ratchet up by an additional 1-6 degrees Celsius, there would be about a 5 percent change, total, by the end of the 21st century. That means that hurricane-force winds are unlikely to exceed 200 mph, Landsea said.

However, Typhoon Nancy in 1961, in the Northwest Pacific Ocean, was said to have maximum sustained winds of 215 mph, according to the World Meteorological Organization's Commission on Climatology, a new clearinghouse for climate records set up at Arizona State University to settle the many disputes on weather and climate extremes. (A typhoon is the same thing as a hurricane, just in a different part of the world.)

There are known records for wind speeds that outstrip anything ever measured in a hurricane. The fastest "regular" wind that's widely agreed upon was 231 mph, recorded at Mount Washington, New Hampshire, on April 12, 1934. During a May 1999 tornado in Oklahoma, researchers clocked the wind at 318 mph.

Fix the scale?

Shortly after Wilma topped out in 2005, Emanuel called the Saffir-Simpson scale irrational, in part because it deals only with wind, ignoring factors such as a storm's size, rainfall potential and forward speed. "I think the whole category system needs serious rethinking," Emanuel told LiveScience then.

But Herbert Saffir, co-creator of the scale, countered that his scale was useful because it was simple. "As simple as it is, I like the scale," Saffir said in a post-Wilma telephone interview. "I don't like to see it too complex."

Here's why no Category 6 was included: The scale was designed to measure the amount of damage inflicted by winds, and beyond 156 mph, the damage begins to look about the same, according to Simpson.

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