A Point of No Return for Greenland's Ice

Every molecule of carbon dioxide added to the atmosphere brings Greenland's ice sheet closer to irreversible melting -- and a sea level rise of more than 20 feet.

A new analysis suggests that if we pass a certain threshold of total emissions, the ice sheet will melt completely, no matter how high or low a peak CO2 concentration is reached or how quickly emissions are reduced afterward.

"A peak warming for a very short period will have an impact, but it might not be enough to cause long-term melting," said John Church of the Center for Australian Weather and Climate Research in Hobart, Australia, who was not a part of the study. "It's a matter of getting the temperatures up and keeping them up."

"We show that it's not really a question of how much CO2 in terms of 700 or 800 ppm [parts per million] in the atmosphere," said study author Gilles Ramstein of the Centre National de la Recherche Scientifique in Gif-sur-Yvette, France "It's really about cumulative doses. That means you can get a deglaciation of Greenland at 700 ppm if you reach this value and stay on that value for a long time."

The researchers used a climate model designed to reach over very long timescales -- tens of thousands of years -- to test the effect of different emissions scenarios on the extent of Greenland ice melting over millennia.

Their results indicate that regardless of the peak CO2 concentration, if total emissions surpass 3,800 billion tons of carbon, the Greenland ice sheet will melt completely over thousands of years. So far, humans have emitted about 380 billion tons of carbon from fossil fuel combustion, according to the researchers.

It will take longer -- perhaps thousands of years longer -- to melt Greenland completely, the longer it takes to reach the threshold. But once the threshold is passed, the melting will be irreversible, because CO2 stays in the atmosphere for hundreds of years, and because positive feedback cycles -- where loss of snow increases heat absorption by darker, exposed surfaces -- will propagate melting.

And, the researchers emphasize, the true threshold may be lower than they calculate.

"What we found here is largely an underestimate," Ramstein said. "We have a model that is quite simple, with coarse resolution so that it can simulate for thousands of years. You might actually get complete melting for lower carbon emissions." The work was published in Geophysical Research Letters.

Scenarios below the 3,800-billion-ton threshold led to a reduction in the ice sheet size of 10 to 63 percent over the course of the simulations, still a concerning loss. "Even one meter of sea level rise is a complete catastrophe," Ramstein said.

"Rates of a meter per century are feasible," Church said, so it will not take thousands of years to feel the effects of melting.

"This is only the northern part of the story," Ramstein added. "There is also a southern part, in Antarctica. In the south there is the ice shelf. This makes west Antarctica very vulnerable to changes."

Pharaonic Boat to Be Excavated, Reassembled

Ancient wood hidden for millennia in an underground chamber beside the Great Pyramid of Khufu in Giza will soon be excavated and reassembled into a unique pharaonic boat, according to Zahi Hawass, chief of Egypt's Supreme Council of Antiquities.

The glorious heap of beams and planks can now be seen for the first time by the public just as it was left by the ancient Egyptians 4,500 years ago -- fully disassembled and carefully stacked. Tourists can view images of the inside of the boat pit from a camera inserted through a hole in the chamber's ceiling.

View a slideshow about the boat here.

"We are currently reviewing a Japanese proposal to fully excavate the wood fragments and rebuild the boat. The project will take five years and will cost $10 million," Hawass told Discovery News in a phone interview.

Archaeologists have long known the existence of a boat buried 10 meters (33 feet) below the last resting place of the 4th dynasty Pharoah Khufu (2589-2566 B.C.), or "Cheops" as the Greeks called him.

Two pits carved into the bedrock came to light in 1954, when a mountain of debris was cleared from the south face of the Great Pyramid.

Almost perfectly preserved, the cedar timbers excavated from the first pit were painstakingly reassembled into an extraordinary boat. About 142 feet long and made of 1,224 components, Khufu's first ship now stands resurrected in a specially built museum near the Great Pyramid.

While evidence of a second pit very near to the first one was noted first in 1954, it took some 31 years before Egyptian authorities investigated the underground chamber by inserting a camera through thick slabs of stone in 1985.

Now a Japanese team from Waseda University, led by Egyptologist Sakuji Yoshimura, has submitted a proposal to excavate, restore, rebuild and transport the boat along with its mate to the Grand Egyptian Museum. Without a prompt intervention, the vessel would be at risk of serious damage, the Japanese team said.

"Although the boat has been sealed in the pit for the last 4,500 years, it seems that in 1954 the archaeologist who discovered it opened a small hole, and insects were able to get inside. These insects may have caused some damage to the wood," Hawass said.

Similarities between the timbers of the first ship and what archaeologists have been able to see from video footage, support the theory that the two were sister ships.

"There is no question about that. The ships are about the same size and probably have the same overall appearance. Both have similar measurements for plank dimensions and fastenings, and both have pre-fabricated cabins for the deck," Cheryl Ward, one of the maritime archaeologists who evaluated the first video footage back in the 1980s, told Discovery News.

Ward, the author of "Sacred and Secular: Ancient Egyptian Ships and Boats," confirmed that the wood, mainly cedar imported from Lebanon, is rather damaged.

"There seems to be less volume of wood compared to the first pit, not because the boat is smaller but because there is more degradation. We did not see any evidence for termites, but one of the first things that we saw actually was a large beetle. So there is an opening somewhere that lets the insects come and go," Ward said.

Beautifully engineered, the boats reveal a level of skill that rivals the pyramids themselves. And like the pyramids, they raise many questions: What was their purpose? Was the embalmed Khufu taken to his pyramid in one of these ships? And why were there two boats? But most of all, why did the ancient Egyptians first build and then disassemble and buried two expensive, full-sized royal ships at the base of the Great Pyramid?

According to Hawass, the boats were symbolic vessels, and were not used in the funerary procession to carry Khufu's body from his palace at Memphis to his tomb at Giza.

"It is my belief that the boats were buried to serve symbolically -- they would transport the dead king on his daily journey with the sun god across the sky," Hawass explained.

The ancient Egyptians believed that the sun traveled from east to west in a "day boat," moving to a "night boat" for the return trip to the underworld.

"The second boat was intended to carry the king across the daytime sky, while the first one was for his night voyage," Hawass said.

He believes that the king would have been thought to travel through a channel that leads from the south side of the King's Chamber of the Great Pyramid.

"The oars would have been used symbolically by the sun god to kill the wild creatures that threatened him on his journey," Hawass said

As for the boat being disassembled -- that wasn't a problem.

"The sun god knew how to reconstruct it. That's why they dismantled these ships and buried them in a pit," Hawass explained.

One of the most interesting aspects about these boats is the technology with which they were built and then dismantled. Basically, they were stored like Ikea furniture -- pre-fabricated and ready for assembly.

In the case of Khufu's first ship, the timbers were carefully placed in the underground chamber, and stacked in a sequence that basically led to the vessel's finished form.

"The Egyptians had a very strong understanding on how to treat, conserve and recycle wood timbers," Ward said. "Amazingly, they were able to take these boats apart and package them for travel."

Oldest Bible Pieced Together

The oldest surviving copy of the New Testament, a 4th century version that had its Gospels and epistles spread across the world, is being made whole again -- online.

The British Library says the full text of the Codex Sinaiticus will be available to Web users by next July, digitally reconnecting parts that are held in Britain, Russia, Germany and a monastery in Egypt's Sinai Desert.

A preview of the Codex, which also has some parts of the Old Testament, will hit the Web on Thursday -- the Book of Psalms and the Gospel of Mark.

"Only a few people have ever had the opportunity to see more than a couple of pages of the (Codex)," said Scot McKendrick, the British Library's head of Western manuscripts. The Web site will give everyone access to a "unique treasure," he said.

Discovered at the Monastery of Saint Catherine at Mount Sinai by German Bible scholar Constantine Tischendorf in the mid-19th century, much of the Codex eventually wound up in Russia -- just how exactly the British Library won't say, citing lingering sensitivity over the circumstances surrounding its removal from the monastery.

The British Library bought 347 pages from Soviet authorities in 1933. Forty-three pages are at the University Library in Leipzig, Germany, and six fragments are at the National Library of Russia in St. Petersburg. And in 1975, monks stumbled on 12 more pages and 40 fragments stashed in a hidden room at the monastery.

Biblical scholars are thrilled at the news that the Codex Sinaiticus -- divided since Tischendorf's trip to the monastery in 1844 -- is finally being put back together, albeit virtually.

In the past, anyone wishing to examine the document first hand would have had to approach the British Library "on bended knee," said Christopher Tuckett, a professor of New Testament studies at Oxford University.

"To have it available just at the click of a button is fantastic," he said. "You could do in two seconds what would take hours and hours of flicking through the leaves."

Handwritten in Greek more than 1,600 years ago -- it isn't exactly clear where -- the surviving 400 or so pages carry a version of the New Testament that has a few interesting differences from the Bible used by Christians today.

The Gospel of Mark ends abruptly after Jesus' disciples discover his empty tomb, for example. Mark's last line has them leaving in fear.

"It cuts out the post--resurrection stories," said Juan Garces, curator of the Codex Sinaiticus Project. "That's a very odd way of ending a Gospel."

James Davila, a professor of early Jewish studies at St. Andrews University in Scotland, said the Codex also includes religious works foreign to the Roman Catholic and Protestant canons -- such as the "Epistle of Barnabas" and the "Shepherd of Hermas," a book packed with visions and parables.

Davila stressed that did not mean the works were necessarily considered Scripture by early Christians: They could have been bound with the Bible to save money.

The Codex itself is a fascinating artifact, representing the best of Western bookmaking, Garces said. The parchment was arranged in little multipage booklets called quires, which were then numbered in sequence.

"It was the cutting edge of technology in the 4th century," he said.

The British Library bound its quires into two volumes after their purchase from the Soviets, one of which is kept on show in a climate--controlled, bulletproof display case. Visitors can peer at the ancient book, but only see two pages at a time.

Dead Baby Penguins Wash Ashore by the Hundreds

Hundreds of baby penguins swept from the icy shores of Antarctica and Patagonia are washing up dead on Rio de Janeiro's tropical beaches, rescuers and penguin experts said Friday.

More than 400 penguins, most of them young, have been found dead on the beaches of Rio de Janeiro state over the past two months, according to Eduardo Pimenta, superintendent for the state coastal protection and environment agency in the resort city of Cabo Frio.

While it is common here to find some penguins -- both dead and alive -- swept by strong ocean currents from the Strait of Magellan, Pimenta said there have been more this year than at any time in recent memory.

Rescuers and those who treat penguins are divided over the possible causes.

Thiago Muniz, a veterinarian at the Niteroi Zoo, said he believed overfishing has forced the penguins to swim further from shore to find fish to eat "and that leaves them more vulnerable to getting caught up in the strong ocean currents."

Niteroi, the state's biggest zoo, already has already received about 100 penguins for treatment this year and many are drenched in petroleum, Muniz said. The Campos oil field that supplies most of Brazil's oil lies offshore.

Muniz said he hadn't seen penguins suffering from the effects of other pollutants, but he pointed out that already dead penguins aren't brought in for treatment.

"Aside from the oil in the Campos basin, the pollution is lowering the animals' immunity, leaving them vulnerable to funguses and bacteria that attack their lungs," Pimenta said, quoting biologists who work with him.

But biologist Erli Costa of Rio de Janeiro's Federal University suggested weather patterns could be involved.

"I don't think the levels of pollution are high enough to affect the birds so quickly. I think instead we're seeing more young and sick penguins because of global warming, which affects ocean currents and creates more cyclones, making the seas rougher," Costa said.

Costa said the vast majority of penguins turning up are baby birds that have just left the nest and are unable to out-swim the strong ocean currents they encounter while searching for food.

Every year, Brazil airlifts dozens of penguins back to Antarctica or Patagonia.

Web-Crawling Program ID's Disease Outbreaks

Scientists are searching within the virtual world and finding real viruses.

Every hour, HealthMap, an infectious disease-tracking Web site, culls through news Web sites, public health list servs, the World Health Organization's online pages, and other Web sites in six different languages to pinpoint outbreaks of disease that real-world doctors can then act on.

"We were originally thinking about how we could expand disease surveillance and pick up outbreaks earlier than traditional methods," said John Brownstein of Harvard Medical School and Children's Hospital Boston, who created HealthMap in September of 2006 with Clark Friefeld, a software developer at Harvard Medical School.

"It was a pilot project, a side gig for us," explained Brownstein.

About nine months ago, HealthMap came to the attention of Google.org, the philanthropic arm of the Internet search giant, which began to fund the team. Then, as Brownstein recalled, "all of a sudden, it just took off."

HealthMap gathers information from the Internet and filters it, removing, for example, duplicated or irrelevant information. It can pinpoint an incident of bubonic plague in Siberia, for example, while ensuring that a "plague" of home foreclosures in northern California doesn't show up on the free access Google Maps.

So far the program identifies about 95 percent of all disease outbreaks, sometimes days before the World Health Organization or the Centers of Disease Control announce them.

The most recent example of this is the ongoing salmonella outbreak in the United States that has sickened more than 1,000 people and the cause of which is still unknown. HealthMap detected the outbreak before the CDC announced anything.

"This will definitely save lives," said Larry Madoff, editor of ProMED, an infectious disease monitoring Web site run by the International Society for Infectious Disease.

"This is a good step forward," said Madoff. "[HealthMap] helps us predict how disease outbreaks will happen."

ProMed, unlike HealthMap, uses human moderators, not mathematical algorithms, who specialize in geographic regions or specific areas of disease to identify public health outbreaks.

HealthMap isn't just for doctors, specialists and public health officials, however. If travelers are heading to Paraguay they can see if there is an instance of Yellow Fever, for instance, and get vaccinated before they leave.

There is room for improvement however, says Madoff -- and Brownstein agrees. The HealthMap team is expanding operations and increasing the amount of detailed information for each particular outbreak and incorporating more "noisy" sources of information, such as blogs and chat rooms.

These sources can be less reliable than traditional sources but could alert authorities to outbreaks much sooner than traditional detection methods.

"We hope to improve that score of 95 percent by picking up that needle in the haystack, the quiet, early indication of potentially serious outbreaks," said Brownstein.

Giant Laser in the Works to Achieve Fusion

In the movie "Spiderman II," the web-slinging hero stops the creation of a tritium-fueled laser fusion machine. Doctor Octopus's theory was right, but his machine was too small.

Scientists at the Lawrence Livermore National Laboratory in California are building their own laser fusion machine that is 10 stories tall, 400 feet long and fueled with tritium (and deuterium).

The goal of the project, known as the National Ignition Facility (NIF), is to create such intense heat and pressure that the fuel, both isotopes of the element hydrogen, will fuse together to form helium.

Researchers expect that reaction will release massive amounts of energy that could one day provide nearly unlimited and environmentally friendly power to the world, advance basic scientific research and ensure the effectiveness of the nation's nuclear warheads.

"It is absolutely essential that we try this," said Richard Petrasso of the Massachusetts Institute of Technology's Plasma Science and Fusion Center who is also working on the NIF.

"If we can in fact achieve fusion and make copious amounts of energy, that would be a clear achievement."

To achieve nuclear fusion, scientists will cool samples of deuterium and tritium -- two isotopes of the element hydrogen that have extra neutrons -- to just above absolute zero in a glass-capped cylinder about the size of a quarter.

Then 192 laser beams, split into two groups, will shine onto the fuel, heating it up to about the point of ignition.

Some of the energy will explode outwards, but some of the energy will further compress the innermost core of the fuel, compressing it so much that two hydrogen atoms will fuse together and create one helium atom.

Nuclear ignition, as Petrasso explains, is like a smoldering log suddenly bursting into flames.

"Once you reach certain conditions of pressure and temperature that log will spontaneously start to burn," said Petrasso. "But the fuel for NIF is nuclear, not chemical, and because of that we will get much more energy."

That reaction powers and creates similar, but controlled conditions found in huge supernovae many times the size of the sun and thermonuclear warheads, both of which will also be research focuses at the NIF, said Bob Hirschfeld, also at the NIF.

Since exploding nuclear warheads both above and below ground is now forbidden, the military has a difficult time telling if its stockpile of nuclear weapons works.

For those worried about the prospect of either a supernovae or thermonuclear explosion stemming from the project, Hirschfeld says not to worry.

"The amount of fuel being used is smaller than a BB," said Hirschfeld. "And the reaction is not self-sustaining," meaning that without the lasers the reaction will fizzle out harmlessly.

The target chamber is also encased in aluminum, then in 16 inches of concrete, which is then encased with another round of concrete.

The lasers can only fire every few hours because of the extreme heat generated by the 500 trillion watts, more than 1,000 times the power generated in the United States at any moment, necessary to power the lasers.

Despite its size and energy consumption, the goal of cheap energy has attracted other countries to nuclear fusion as well.

Scientists in France and the U.K. are working on other laser-based fusion plans. Other groups, notably the ITER experiment to be based in France, are trying to reach ignition through magnetic fields.

However nuclear fusion is achieved, the result would be a boon for humanity.

"The great thing about fusion is the fuel is widely available to all nations, it's a relatively benign form of energy, and there isn't long-lived radioactive waste," said Ron Davidson of Princeton University who is not involved in the NIF.

"It would be a great scientific step forward if the NIF achieves ignition and I personally believe that they will."

Fast-Spoiling Pear Mystery Solved

Pears spoil more quickly than apples because they're out of breath, according to European researchers.

The finding could lead to new ways of storing pears to prevent them from rotting on the way to the fruit bowl.

Pieter Verboven and his colleagues from the Catholic University of Leuven in Belgium and the European Synchrotron Radiation Facility (ESRF) have published the findings in the journal Plant Physiology.

After being picked from the tree, apples and pears continue to 'breathe.' To keep the fruit healthy, a minimum level of oxygen must be supplied to all of its cells. If this does not happen, the fruit turns brown.

To understand why pears spoil more quickly than apples, Verboven and his team placed samples of each fruit in the path of a synchrotron beam. The beam was used to create 3D images that have a resolution of one thousandth of a millimeter.

Researchers have hypothesized that apples and pears contain microscopic pathways between each cell, thereby allowing oxygen to pass into the fruit.

The synchrotron images revealed that apples contain large, irregular cavities between cells, while in pears the cavities have the shape of tiny, interconnected channels.

They found the voids in apple were often larger than the surrounding cells, and some cells were not connected to voids.

In comparison, the voids inside pears were smaller than the cells. Each cell was surrounded by a tight and continuous network of voids.

"It is still unclear how airways in the fruit develop and why apples have cavity structures and pears micro-channel networks," said Verboven.

"The micro-channels are so small that oxygen supply to the fruit core is very limited, and cells are quickly 'out of breath' when oxygen levels fall below the safety threshold," he added.

The researchers believe their results provide a better understanding of how the fruit degrades after harvest and explain why pears are more susceptible to decay during storage.

It is hoped the research can also be used in computer models to calculate oxygen concentration in individual cells of fruit tissues.

Sleep-Deprived? You Might Sound Drunk

Lack of sleep alters the brain to such a degree that it can be heard in the way a person speaks, according to a new study that found sleep-deprived people sound almost drunk.

Bystanders might describe this type of speech as "tired-sounding" or "slurred," but experts studying the phenomenon say those descriptions aren't quite accurate.

"Slurred speech is an extreme form of unclearly articulated speech," lead author Suzanne Boyce told Discovery News.

"The differences we pick up are much less extreme, but they go in the same direction," added Boyce, a professor in the Department of Communication Sciences and Disorders at the University of Cincinnati. "We'd call it 'faintly blurred,' rather than 'slurred,' speech."

Boyce and her team theorized that the differences between the speech of people lacking sleep and those who had a good night's rest would be comparable to the differences between conversational and "clear" speakers.

"Clear" speech occurs when a person articulates or even over-emphasizes syllables, words and phrases -- such as when addressing a formal gathering, talking to people who are hard of hearing or for whom the spoken language is not their native tongue.

A word like "police," for example, might sound more like "blees" in conversational speech, but like "poe-lees" in clear speech.

Boyce explained that "the process is largely subconscious," but when people articulate more "they add more acoustic information bits to the acoustic signal." Computers can then detect these bits of information and note "landmarks," such as marking the puff of air released by the mouth when producing "t" or "k" sounds.

The researchers documented these changes and then applied the same analysis to recordings of test subjects who read sentences aloud and were asked to give driving directions approximately 10 hours since last sleep, then 34 and, finally, 58 hours.

The participants were allowed to eat and drink water, but not coffee or cola.

The findings were recently presented at the Acoustics08 meeting in Paris.

As expected, the sleep-deprived speakers gradually lost their ability to articulate, producing fewer detectible landmarks. Oddly enough, however, when such people hear themselves, they think they sound fine.

Boyce explained that "people lose awareness of how clearly they are speaking when they are tired." In the future, the research may be used to train 911 employees, communication professionals, and therapists who work with the hearing impaired.

Outside listeners, however, appear to have no trouble figuring out that the speaker missed some sleep.

"Listeners seem to clue in on other aspects, like sighs, long breaths and pauses in the recording, or even yawns, if they are audible," Boyce said, adding that if the person can see the speaker, they may also detect visual cues, "like posture, skin tone, eye gaze" and more.

Although not an optimal solution, Wake Forest University School of Medicine scientists have shown that the effects of sleep deprivation can be reversed when given a dose of the naturally occurring brain peptide orexin-A. This chemical, normally secreted by brain neurons, regulates sleep. The brains of sleep-deprived people produce it, but often not enough to achieve full alertness.

"These findings are significant because of their potential applicability," said Samuel Deadwyler, a professor of physiology and pharmacology at Wake Forest.

"This could benefit patients suffering from narcolepsy and other serious sleep disorders," he said, "but it also has applicability to shift workers, the military and many other occupations where sleep is often limited, yet cognitive demand remains high."

'Middle Earth' Mountains: Steep and Strong

It's the composition of the rocks, not elfin magic, that makes New Zealand's mountains some of the steepest on Earth -- without being particularly prone to landslides.

A new survey of the mountain ranges that form the spine of New Zealand confirms the steepest are made almost entirely of tough but otherwise unexciting rocks called greywackes and schists.

The lack of variety, paired with a great range of climates and mountain growth rates throughout the ranges, makes the region an ideal test of the importance of rock types in determining how often the slopes fail and generate killer landslides.

"They're pretty boring rocks," confirmed avalanche and landslide researcher Oliver Korup of the Swiss Federal Research Institutes in Davos, Switzerland. They are simply petrified deep sea sediments that have been pushed up to form the mountains, he said. "They don't even have fossils."

Korup is the author a paper on the New Zealand mountains in the July issue of Geophysical Research Letters.

In general, there are three things that control the steepness of mountain slopes: 1) the rate the mountains are being uplifted, or growing, 2) the rate that erosion is wearing the mountains away, and 3) the strength of the rocks, as measured by their ability to pile up without collapsing as a landslide.

By measuring slopes and landslide frequencies in New Zealand, Korup found that regardless of the growth rates or rainfall in a particular mountain range, the slopes tend to be steeper than mountains elsewhere in the world. That suggests the only other variable -- rock type -- is especially important.

That is not, however, the way many geomorphologists have seen it in recent years, particularly when using computers to model landscape changes, explained geologist David Montgomery of the University of Washington.

"The funny thing is," agreed Korup, "a lot of these sophisticated models know a lot about the physics of erosion, but not rock types."

His New Zealand study suggests that's a big omission. In fact, it turns the erosion-based approach to interpreting landscapes almost on its head.

"You might be able to look at a mountain range and explain the slopes by the different rock types," said Montgomery.

Korup hopes that someone will look at another fairly homogeneous mountain belt somewhere else to see how well this idea holds up. The Olympic Range in Washington, he suggested, might be a good candidate.

Invisible Carpet Idea Close to Actual Invisibility

Invisibility cloaks are cool, but an invisibility carpet is more practical.

That's according to scientists from Imperial College London, who recently published a paper detailing the creation of a material that would be the first to hide objects in visible light, something no cloaking device has ever achieved.

"We've given a prescription for how to cloak something in visible light," said John Pendry, who, along with Jensen Li, wrote the paper that appeared recently on ArXiv.org. "It will be difficult to make but it is also practical."

Cloaking an object requires structures, often referred to as metamaterials, that channel light in a specific way.

The only way to channel light in that fashion is by using structures smaller than the wavelength of light being used to detect an object. In 2006, Duke University scientists cloaked an object from light centimeters long by creating a metamaterial with structures millimeters in size.

To cloak an object in visible light, which has a much smaller wavelength, around half a micron, scientists would have to create structures nanometers in size, which, according to Pendry, "requires some clever nanotechnology."

That nanotechnology would come from combining special layers of common silica and silicon, each of which reflects light differently.

"It's a lot like a mirage," said Pendry. "The sun heats the air above the desert and creates a temperature gradient, so when light from the sky comes down the graded refraction bends the light and it enters your eye and you see a mirage the looks like water."

Instead of creating a temperature gradient that only partially reflects light, the silicon and silica mix would create a physical gradient that instead makes light do a complete U turn, exiting in the same direction it entered.

The result would look like a mirror. If you looked at it you would see your reflection. The difference is that this mirror would let you check your reflection from any angle, not just one.

"This new cloak is not perfect," said Vladimir Shalaev, a professor at Purdue University in Indiana involved in metamaterial research who did not contribute to the ArXiv.org paper.

"Instead it leaves an observer with illusion that there is only a flat mirror on the ground with some transparent dielectric box on top of it, whereas, in reality, there an object concealed in the "transparent" box which is not visible for the observer."

Perfect or not, it's still an important result according to Shalaev.

"This 'invisibility carpet' can be fabricated and it's indeed an important step toward making the dream of invisibility true."

Theory and actual fabrication are far apart, however. Pendry estimates that with appropriate funding and expertise, invisibility carpets could be produced in one to two years.

"We are theorists; we have an easy life," said Pendry. "The difficult stuff is to actually make this."