Molecule in earth's atmosphere could "cool the planet"

Scientists have shown that a newly discovered molecule in Earth's atmosphere has the potential to play a significant role in off-setting global warming by cooling the planet.

In a breakthrough paper published in Science, researchers from The University of Manchester, The University of Bristol and Sandia National Laboratories report the potentially revolutionary effects of Criegee biradicals.

These invisible chemical intermediates are powerful oxidisers of pollutants such as nitrogen dioxide and sulfur dioxide, produced by combustion, and can naturally clean up the atmosphere.

Although these chemical intermediates were hypothesised in the 1950s, it is only now that they have been detected. Scientists now believe that, with further research, these species could play a major role in off-setting climate change.

The detection of the Criegee biradical and measurement of how fast it reacts was made possible by a unique apparatus, designed by Sandia researchers, that uses light from a third-generation synchrotron facility, at the Lawrence Berkeley National Laboratory's Advanced Light Source.

The intense, tunable light from the synchrotron allowed researchers to discern the formation and removal of different isomeric species -- molecules that contain the same atoms but arranged in different combinations.

The researchers found that the Criegee biradicals react more rapidly than first thought and will accelerate the formation of sulphate and nitrate in the atmosphere. These compounds will lead to aerosol formation and ultimately to cloud formation with the potential to cool the planet.

The formation of Criegee biradicals was first postulated by Rudolf Criegee in the 1950s. However, despite their importance, it has not been possible to directly study these important species in the laboratory.

In the last 100 years, Earth's average surface temperature increased by about 0.8 °C with about two thirds of the increase occurring over just the last three decades.

Most countries have agreed that drastic cuts in greenhouse gas emissions are required, and that future global warming should be limited to below 2.0 °C (3.6 °F).

Dr Carl Percival, Reader in Atmospheric Chemistry at The University of Manchester and one of the authors of the paper, believes there could be significant research possibilities arising from the discovery of the Criegee biradicals.

He said: "Criegee radicals have been impossible to measure until this work carried out at the Advanced Light Source. We have been able to quantify how fast Criegee radicals react for the first time.

"Our results will have a significant impact on our understanding of the oxidising capacity of the atmosphere and have wide ranging implications for pollution and climate change.

"The main source of these Criegee biradicals does not depend on sunlight and so these processes take place throughout the day and night."

Professor Dudley Shallcross, Professor in Atmospheric Chemistry at The University of Bristol, added: "A significant ingredient required for the production of these Criegee biradicals comes from chemicals released quite naturally by plants, so natural ecosystems could be playing a significant role in off-setting warming."

Electron's negativity cut in half by supercomputer

Simulations Slice Electron in Half -- A Physical Process That Cannot Be Done in Nature.

While physicists at the Large Hadron Collider smash together thousands of protons and other particles to see what matter is made of, they're never going to hurl electrons at each other. No matter how high the energy, the little negative particles won't break apart. But that doesn't mean they are indestructible.

Using several massive supercomputers, a team of physicists has split a simulated electron perfectly in half. The results, which were published in the Jan. 13 issue of Science, are another example of how tabletop experiments on ultra-cold atoms and other condensed-matter materials can provide clues about the behavior of fundamental particles.

In the simulations, Duke University physicist Matthew Hastings and his colleagues, Sergei Isakov of the University of Zurich and Roger Melko of the University of Waterloo in Canada, developed a virtual crystal. Under extremely low temperatures in the computer model, the crystal turned into a quantum fluid, an exotic state of matter where electrons begin to condense.

Many different types of materials, from superconductors to superfluids, can form as electrons condense and are chilled close to absolute zero, about -459 degrees Fahrenheit. That's approximately the temperature at which particles simply stop moving. It's also the temperature region where individual particles, such as electrons, can overcome their repulsion for each other and cooperate.

The cooperating particles' behavior eventually becomes indistinguishable from the actions of an individual. Hastings says the phenomenon is a lot like what happens with sound. A sound is made of sound waves. Each sound wave seems to be indivisible and to act a lot like a fundamental particle. But a sound wave is actually the collective motion of many atoms, he says.

Under ultra-cold conditions, electrons take on the same type of appearance. Their collective motion is just like the movement of an individual particle. But, unlike sound waves, cooperating electrons and other particles, called collective excitations or quasiparticles, can "do things that you wouldn't think possible," Hastings says.

The quasiparticles formed in this simulation show what happens if a fundamental particle were busted up, so an electron can't be physically smashed into anything smaller, but it can be broken up metaphorically, Hastings says.

He and his colleagues divided one up by placing a virtual particle with the fundamental charge of an electron into their simulated quantum fluid. Under the conditions, the particle fractured into two pieces, each of which took on one-half of the original's negative charge.

As the physicists continued to observe the new sub-particles and change the constraints of the simulated environment, they were also able to measure several universal numbers that characterize the motions of the electron fragments. The results provide scientists with information to look for signatures of electron pieces in other simulations, experiments and theoretical studies.

Successfully simulating an electron split also suggests that physicists don't necessarily have to smash matter open to see what's inside; instead, there could be other ways to coax a particle to reveal itself.

Mystery of source of supernova in nerby galaxy solved

Using NASA's Hubble Space Telescope, astronomers have solved a longstanding mystery of the type of star, or so-called progenitor, which caused a supernova seen in a nearby galaxy. The finding yields new observational data for pinpointing one of several scenarios that trigger such outbursts.

Based on previous observations from ground-based telescopes, astronomers knew that a kind of supernova called a Type Ia supernova created a remnant named SNR 0509-67.5, which lies 170,000 light-years away in the Large Magellanic Cloud galaxy.

The type of system that leads to this kind of supernova explosion has long been a high importance problem with various proposed solutions but no decisive answer. All these solutions involve a white dwarf star that somehow increases in mass to the highest limit.

Astronomers failed to find any companion star near the center of the remnant, and this rules out all but one solution, so the only remaining possibility is that this one Type Ia supernova came from a pair of white dwarfs in close orbit.

"We know that Hubble has the sensitivity necessary to detect the faintest white dwarf remnants that could have caused such explosions," said lead investigator Bradley Schaefer of Louisiana State University (LSU) in Baton Rouge. "The logic here is the same as the famous quote from Sherlock Holmes: 'when you have eliminated the impossible, whatever remains, however improbable, must be the truth.'"

The cause of SNR 0509-67.5 can be explained best by two tightly orbiting white dwarf stars spiraling closer and closer until they collided and exploded.

The results are being reported January 11 at the meeting of the American Astronomical Society in Austin, Texas. A paper on the results will be published in the Jan. 12 issue of the journal Nature.

For four decades, the search for Type Ia supernovae progenitors has been a key question in astrophysics. The problem has taken on special importance over the last decade with Type Ia supernovae being the premier tools for measuring the accelerating universe.

Type Ia supernovae are tremendous explosions of energy in which the light produced is often brighter than a whole galaxy of stars. The problem has been to identify the type of star system that pushes the white dwarf's mass over the edge and triggers this type of explosion. Many possibilities have been suggested, but most require that a companion star near the exploding white dwarf be left behind after the explosion.

Therefore, a possible way to distinguish between the various progenitor models has been to look deep in the center of an old supernova remnant to search for the ex-companion star.

In 2010, Schaefer and Ashley Pagnotta of LSU were preparing a proposal to look for any faint ex-companion stars in the center of four supernova remnants in the Large Magellanic Cloud when they discovered that the Hubble Space Telescope had already taken the desired image of one of their target remnants, SNR 0509-67.5, for the Hubble Heritage program, which collects images of especially photogenic astronomical targets.

In analyzing the central region, they found it to be completely empty of stars down to the limit of the faintest objects that Hubble can detect in the photos. Schaefer reports that the best explanation left is the so-called "double degenerate model" in which two white dwarfs collide.

There are no recorded observations of the star exploding. However, researchers at the Space Telescope Science Institute in Baltimore, Md., have identified light from the supernova that was reflected off of interstellar dust, delaying its arrival at Earth by 400 years. This delay, called a light echo of the supernova explosion also allowed the astronomers to measure the spectral signature of the light from the explosion. By virtue of the color signature, astronomers were able to prove it was a Type Ia supernova.

Because the remnant appears as a nice symmetric shell or bubble, the geometric center can be accurately determined. These properties make SNR 0509-67.5 an ideal target to search for ex-companions. The young age also means that any surviving stars have not moved far from the site of the explosion.

The team plans to look at other supernova remnants in the Large Magellenic Cloud to further test their observations.

30-story building built in 15 days

What can you accomplish in 360 hours?

The Chinese sustainable building company, Broad Group, has yet attempted another impossible feat, building a 30-story tall hotel prototype in 360 hours, after building a 15-story building in a week earlier in 2011.

You may ask why in a hurry, and is it safe? The statistics in the video can put you in good faith. Prefabricated modular buildings has many advantages over conventional buildings.

Higher precision in fabrication (+/- 0.2mm).
More coordinated on-site construction management.
Shorter construction time span.
Lower construction waste.
Also many other health and energy features are included in Broad Sustainable Buildings (BSB)

The building was built over last Christmas time and finished before New Years Eve of 2012.


An Introduction to BROAD SUSTAINABLE BUILDING CO., LTD Jan.11, 2012
Established in March, 2009, BROAD SUSTAINABLE BUILDING CO., LTD is a wholly-owned subsidiary of BROAD Group, solely operates the magnitude-9 earthquake resistant, 5x more energy efficient, 20x purer air, 90% factory-built, and 1% construction waste Broad Sustainable Buildings (BSB).

BSB headquarter and its R&D Center are situated in the Xiangyin County of Hunan Province in Southern China, with 80,000sqm workshops, 900 employees in 2011. In 2012 with 220,000sqm workshops, 12,000 employees, and in 2013 with 360,000sqm workshops and 19,000 employees, reaching an annual production and installation capacity of 10 million sqms. BSB's central goal is:

1. Improving R&D of BSB technologies, setting up supply chains
2. Sell BSBs in compliance with local regulations in the Hunan building market.
3. Transfer BSB technology to 100 partnership enterprise, every Chinese province and distributed evenly in each nation worldwide.

By December, 2011, BSB technology reached finalization, altogether with 12 BSBs built in Changsha, Xiangyin, Shanghai, Zhejiang and Mexico and developed 2 franchise partners in Ningxia and Fujian with identical factory sizes to the Xiangyin BSB Factory. Another 10 Chinese & international potential partners are in negotiation.

BROAD envisions in the near future, there will be one BSB among three buildings worldwide, allowing all men and women to share BSB's solace. Proving that by responsible use of technology, earth's environment and human living can be elevated simultaneously.

In a squeeze

Elements under pressure reveal secrets of extreme chemistry.

Bruce Banner isn’t the only scientist who could crush you with one mighty squeeze. These days, the Hulk’s superhuman strength is matched by researchers who squish all kinds of stuff in superscience experiments.

The goal isn’t to save the world from baddies, but to explore new frontiers in the nature of matter. After all, most material in the universe exists at bone-crushing pressures. Think massive stars and planetary cores — realms no comic book fan or other Earth dweller has ever seen.

Deep within the planet, rock experiences pressures more than 1 million times as great as the “1 atmosphere” that ordinary humans live under at sea level. Pressures at the centers of ultradense neutron stars are some trillion quadrillion times greater. Under such extreme conditions, atoms themselves begin to buckle.

To mimic these hellish realms, scientists are ramping up pressure in the lab, like the Hulk getting ever stronger as he gets madder. In the process, they’re squeezing out some surprising insights.

One team has found a new kind of iron oxide, a compound that somehow had never been seen before, even though it contains two of the most common elements in Earth’s crust. Another group argues that hydrogen’s odd behavior at high pressures means that the cores of giant gas planets, such as Jupiter, are eroding in a slow hydrogen drip. Meanwhile scientists at the National Ignition Facility in Livermore, Calif., have squeezed diamond to record pressures, uncovering unexpected and exotic behaviors.

Chemistry, it seems, is a different beast under high pressure. “We’re developing a whole new paradigm for understanding the nature of matter,” says Russell Hemley, a chemist at the Carnegie Institution for Science in Washington, D.C.

Hydrogen crush

The idea of squeezing materials to see what happens dates back at least to the 17th century, when British chemist Robert Boyle discovered that doubling the pressure on an ideal gas halved its volume. Around the same time, researchers at the Accademia del Cimento, a scientific society in Florence, Italy, were exploring whether liquids, too, could be compressed. The scientists filled a metal sphere with water and banged it with a hammer. Perhaps not surprisingly, the sphere leaked. But that experiment, Hemley says, set the stage for far more technologically adept investigations.

By the 20th century scientists knew that ordinary matter — be it solid, liquid or gas — behaves according to chemical rules laid out by its electrons, those negatively charged particles that buzz around atomic nuclei in well-defined regions known as orbitals. It turns out that squishing matter doesn’t just compress its atoms so that they stack closer together, like a pile of well-arranged oranges at a farmers market. Compression also radically alters electron orbitals, in different ways depending on their original shapes.

Suddenly electrons can zip around in places they haven’t been before, and the rules typically governing the periodic table of the elements go out the window.

Perhaps the poster child for odd behavior at high pressures is hydrogen, the most common element in the universe. As the simplest element, with just one proton in its nucleus and one orbiting electron, hydrogen seems like it should behave in a straightforward way. But recent experiments have shown that, like Bruce Banner, it suffers from multiple personalities.

Most intriguing, scientists say, is the fact that if you squeeze hydrogen hard enough, this flighty gas transforms into a dense fluid whose electrons move in an ill-defined sea, allowing it to conduct electricity and behave as a metal. Understanding how two atoms linked as a gaseous H2 molecule split and form single atoms flowing as a liquid could illuminate what happens to more complicated molecules under pressure, says physicist Alexander Goncharov of Carnegie. “Once we understand that simple system, others may become simpler,” he says.

Goncharov, Hemley and many other scientists probe hydrogen and other materials by crushing them between two small diamonds in a machine known as a diamond anvil cell. The pointy ends of the cut diamonds narrow to a tiny tip where, when squeezed together, the pressure soars. In a small dent where the diamonds meet, an injected sample can be compressed to unfathomably high pressures.

Using such a device, scientists at the Max Planck Institute for Chemistry in Mainz, Germany, announced in Nature Materials in November that they had created metallic hydrogen at room temperature and pressures around 2.6 million times Earth’s atmosphere (SN: 12/17/11, p. 9). If confirmed, the discovery would fulfill a long-sought goal; scientists first predicted the existence of metallic hydrogen in 1935.

But some experts are withholding judgment on the new work. It’s one thing to squeeze materials at high pressures and see something unusual; it’s another to establish conclusively what that unusual observation means. Several researchers say they have data that contradict the metallic hydrogen claim, but they do not want to discuss their work in detail until it appears in peer-reviewed journals.

The Max Planck group, led by Mikhail Eremets, is involved in another high-pressure disagreement. In a paper appearing in Science in 2008, Eremets’ team, along with colleagues from the University of Saskatchewan in Canada, reported that a mix of silicon and hydrogen became superconducting at high pressures. This compound, known as silane, is made of one silicon atom bonded with four hydrogen atoms. As an industrial compound, silane is used as a coating agent, a water repellent and in other applications. But mash it in a diamond anvil cell, and at around 960,000 atmospheres it starts allowing electrons to flow freely, the researchers reported.

Not so fast, other scientists said. One challenge with studying hydrogen is that at high enough pressures and temperatures, it starts reacting with just about everything around it — even elements that are usually chemically inert. Theorists led by Duck Young Kim, now at Carnegie, have reported that hydrogen may hook up with famously unreactive platinum at pressures around 210,000 atmospheres. At higher pressures, 700,000 atmospheres or above, this newborn platinum hydride may even start to superconduct, shuttling electrons without resistance, the scientists wrote in September in Physical Review Letters.

Such a mix of platinum and hydrogen could explain the superconductivity reported in silane, an international team argued in August in Physical Review B. The team’s calculations suggest that platinum hydride could form as the silane breaks apart into silicon and hydrogen — and that hydrogen reacts with platinum electrodes used in the experiment. One particular crystal form of platinum hydride, the scientists say, could explain the superconductivity supposedly observed.

Eremets’ team stands by its work, but the experience underscores how complicated high-pressure science can be.

Core compression

Despite the difficulties involved in working under extreme conditions in the lab, it is still the only way to figure out what’s happening in many places in the universe, including the ground under people’s feet. For geologists, high-pressure experimentation is about as close as they will ever get to a journey to the center of the Earth. And the latest high-pressure studies show how many surprises still lurk there.

Iron, for instance, is the fourth most abundant element in the Earth’s crust and makes up nearly all of the planet’s core. Yet researchers have only now discovered an entirely new iron compound; it contains four atoms of iron and five of oxygen and exists only at high pressure.

Barbara Lavina of the University of Nevada, Las Vegas and colleagues synthesized this compound in a diamond anvil cell by smooshing a different compound made of iron, carbon and oxygen. The compound began to break apart, and at about 100,000 atmospheres and 1,800 kelvins (1,500˚ Celsius) a new type of crystal appeared.

Other iron oxides are common in nature, but this was the first time this particular chemical combination had been seen. “It was thrilling for me just to write the formula Fe4O5,” says Lavina, whose report appeared October 18 in the Proceedings of the National Academy of Sciences.

Understanding the details of how iron and oxygen atoms bond with one another may also reveal key properties of the Earth’s innards, such as how heat flows within the planet. One mineral crucial to revealing these details is wüstite, or FeO. Independent teams at the University of Chicago and Osaka University in Japan recently squeezed wüstite and found that it conducts electricity at pressures and temperatures similar to those found in the planet’s outer core and lower mantle, the layer just above the core.

Pockets rich in wüstite may exist at the core-mantle boundary, where the mineral may transfer heat from the core into more shallow depths, says Chicago’s Rebecca Fischer. Metallic FeO could also help explain why oxygen dissolves in metal more readily at high pressures, such as in the planet’s core, Fischer’s team reports in an upcoming Geophysical Research Letters.

The world of high-pressure discovery also extends well beyond Earth — to other planets in the solar system, and on to other planetary systems. In particular, the cores of gas giant planets are “the least accessible but in many ways the most important objects in the solar system,” says Hugh Wilson, a planetary chemist at the University of California, Berkeley. The very existence of the cores allowed Jupiter and Saturn to coalesce around them; the gravitational pull of the completed gas giants then helped dictate how the rest of the solar system grew.

Yet scientists don’t know much about how the giant planet cores formed. In principle, they were born as bits of rock and ice swirling around the newborn sun began to glom together, becoming big enough to start attracting hydrogen and helium gas to make up the rest of the planet. Today researchers don’t agree on how big the cores are, much less the conditions that exist inside them.

One new idea, born from some high-pressure theoretical calculations involving hydrogen, even suggests that giant planet cores are slowly dissolving away. Over time, watery ice in Jupiter’s core dissolves in the hydrogen-rich material swirling above so that the core shrinks, Wilson and Burkhard Militzer, also of Berkeley, write in an upcoming Astrophysical Journal. “What’s going on inside Jupiter is more complicated and less homogeneous than had been taken into account in previous models,” Wilson says.

The work may even shed light on planets in other solar systems, which astronomers have glimpsed only indirectly so far. Many known exoplanets are more massive than Jupiter, and so they are also hotter inside. Cores of these exoplanets would have started eroding away even faster than Jupiter’s, Wilson says. As a result, elements may have leached from the core and become well-mixed in the gassy atmosphere. One day, if astronomers on Earth can get a detailed picture of an exoplanet’s atmosphere from afar, they may need to account for such internal chemical mixing in order to properly understand what they’re seeing.

The squeeze machine

In perhaps the ultimate test of high-pressure science, researchers are gearing up to squeeze things at the world’s most powerful laser machine. The three-football-field-long National Ignition Facility will focus 192 laser beams on a single tiny target. The eventual goal is to fuse the nuclei of hydrogen atoms, thus harnessing in the lab what the sun and billions of other stars do daily.

But for now, as NIF ramps up toward full power, other scientists are taking advantage of early, prefusion tests to see what happens to materials put in the path of the beams. “NIF is uniquely capable of trying to explore this realm of compression science,” says Jon Eggert, a material scientist at the lab.

This spring, NIF scientists squished diamond in the facility’s laser beams to pressures up to a crushing 50 million atmospheres — more than double the previous record set using a different compression technique by the OMEGA laser at the University of Rochester. So far, Eggert and his colleagues have seen stress patterns appear in diamond crystals that no one has seen before. The researchers have also put tantalum into the machine and spotted what may be a new transition between crystal forms at around 3.4 million atmospheres.

Later this year, the NIF team plans to squeeze materials at 100 million atmospheres. In theory, NIF could approach or exceed the pressure required to seriously disrupt the shell structure of atoms, called the atomic unit of pressure. That would come at around 300 million atmospheres, Eggert says, and would bring with it breakthrough insights into how matter behaves under such conditions. But it’s still not clear, he says, whether the geometry of how the laser beams come together will allow the team to achieve the atomic unit of pressure.

No matter how high the NIF manages to go, Hemley says, it and the other experiments will continue to uncover new surprises. “Exploring these simple planetary materials under extreme conditions is really deepening our understanding of chemistry,” he says. “A lot of what we thought we knew is wrong.”

Researchers create a wire four atoms wide, one atom tall

The smallest wires ever developed in silicon -- just one atom tall and four atoms wide -- have been shown by a team of researchers from the University of New South Wales, Melbourne University and Purdue University to have the same current-carrying capability as copper wires.

Experiments and atom-by-atom supercomputer models of the wires have found that the wires maintain a low capacity for resistance despite being more than 20 times thinner than conventional copper wires in microprocessors.

The discovery, which was published in this week's journal Science, has several implications, including:

For engineers it could provide a roadmap to future nanoscale computational devices where atomic sizes are at the end of Moore's law. The theory shows that a single dense row of phosphorus atoms embedded in silicon will be the ultimate limit of downscaling.
For computer scientists, it places donor-atom based silicon quantum computing closer to realization.
And for physicists, the results show that Ohm's Law, which demonstrates the relationship between electrical current, resistance and voltage, continues to apply all the way down to an atomic-scale wire.

Bent Weber, the paper's lead author and a graduate student in the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales, was thrilled with the finding.

"It's extraordinary to show that Ohm's Law, such a basic law, still holds even when constructing a wire from the fundamental building blocks of nature -- atoms," he says.

The innovation of the Australian group was to build the circuits up atom by atom, instead of the current method of building microprocessors, in which material is stripped away, says Gerhard Klimeck, a Purdue professor of electrical and computer engineering and director of the Network for Computational Nanotechnology.

"Typically we chip or etch material away, which can be very expensive, difficult and inaccurate," Klimeck says. "Once you get to 20 atoms wide you have atomic flucuations that make scaling difficult. But this experimental group built devices by placing atomically thin layers of phosphorus in silicon and found that with densely doped phosphorus wires just four atoms wide it acts like a wire that conducts just as well as metal."

The goal of the research is to develop future quantum computers in which single atoms are used for the computation, says Michelle Simmons, director of the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales and the project's principal investigator.

"We are on the threshold of making transistors out of individual atoms," Simmons says. "But to build a practical quantum computer we have recognized that the interconnecting wiring and circuitry also needs to shrink to the atomic scale."

Hoon Ryu, a Purdue graduate who is now a senior researcher with the Korea Institute of Science and Technology's Supercomputing Center, said the practicality of the research is exciting.

"The metallic wire is in principle quite difficult to be scaled into one- to two-nanometer pitch, but in both experimental and modeling views, the research result is quite remarkable," Ryu says. "For the first time, this demonstrates the possibility that densely doping wire is a viable alternative for the next-gerenation, ultra-scale metallic interconnect in silicon chips."

To assist the Australian researchers, Klimeck's research team ran hundreds of simulations to study the variability of these nanoscale structures.

"Having the throughput capability for a highly scalable code is important for doing that, and we have that capability here at Purdue with http://nanoHUB.org/

 

," Klimeck says. "We ran hundreds of cases to understand the potential landscape of these devices, so this was computationally intensive work."

Klimeck says that in addition to the project's scientific and engineering implications, he found the collaboration the most rewarding aspect.

"It is an exciting collaboration," he says. "We were doing simulations of experimental work, which was based on a theoretical model. So we were bringing the three legs of modern science together in one project. Plus, our graduate students are able to stay in contact and work with each other despite working in various locations around the world. It's hard to think of a better example of how science is done today."

Now you see it, now you don't: researchers cloak a moment in time

Think Harry Potter movie magic: Cornell researchers have demonstrated a "temporal cloak" -- albeit on a very small scale -- in the transport of information by a beam of light.

The trick is to create a gap in the beam of light, have the hidden event occur as the gap goes by and then stitch the beam back together. Alexander Gaeta, Cornell professor of applied and engineering physics, and colleagues report their work entitled "Demonstration of temporal cloaking," in the journal Nature (Jan. 5, 2012.)

The researchers created what they call a time lens, which can manipulate and focus signals in time, analogous to the way a glass lens focuses light in space. They use a technique called four-wave mixing, in which two beams of light, a "signal" and a "pump," are sent together through an optical fiber. The two beams interact and change the wavelength of the signal. To begin creating a time gap, the researchers first bump the wavelength of the signal up, then by flipping the wavelength of the pump beam, bump it down.

The beam then passes through another, very long, stretch of optical fiber. Light passing through a transparent material is slowed down just a bit, and how much it is slowed varies with the wavelength. So the lower wavelength pulls ahead of the higher, leaving a gap, like the hare pulling ahead of the tortoise. During the gap the experimenters introduced a brief flash of light at a still higher wavelength that would cause a glitch in the beam coming out the other end.

Then the split beam passes through more optical fiber with a different composition, engineered to slow lower wavelengths more than higher. The higher wavelength signal now catches up with the lower, closing the gap. The hare is plodding through mud, but the tortoise is good at that and catches up. Finally, another four-wave mixer brings both parts back to the original wavelength, and the beam emerges with no trace that there ever was a gap, and no evidence of the intruding signal.

None of this will let you steal the crown jewels without anyone noticing. The gap created in the experiment was 15 picoseconds long, and might be increased up to 10 nanoseconds, Gaeta said. But the technique could have applications in fiber-optic data transmission and data processing, he added. For example, it might allow inserting an emergency signal without interrupting the main data stream, or multitasking operations in a photonic computer, where light beams on a chip replace wires.

The experiment was inspired by a theoretical proposal for a space-time cloak or "history editor" published by Martin McCall, professor of physics at Imperial College in London, in the Journal of Optics in November 2010. "But his method required an optical response from a material that does not exist. Now we've done it in one spatial dimension. Extending it to two [that is, hiding a moment in an entire scene] is not out of the realm of possibility. All advances have to start from somewhere," Gaeta says.