Building ‘invisible’ materials with light brings science fiction cloaking devices one step closer to reality

A new technique which uses light like a needle to thread long chains of particles could help bring sci-fi concepts such as cloaking devices one step closer to reality.

                                                          Image Credit: Ventsislav Valev

This level of control opens up a wide range of potential practical applications

A new method of building materials using light, developed by researchers at the University of Cambridge, could one day enable technologies that are often considered the realm of science fiction, such as invisibility cloaks and cloaking devices.

Ventsislav Valev

Although cloaked starships won’t be a reality for quite some time, the technique which researchers have developed for constructing materials with building blocks a few billionths of a metre across can be used to control the way that light flies through them, and works on large chunks all at once. Details are published in the journal Nature Communications.

The key to any sort of ‘invisibility’ effect lies in the way light interacts with a material. When light hits a surface, it is either absorbed or reflected, which is what enables us to see objects. However, by engineering materials at the nanoscale, it is possible to produce ‘metamaterials’: materials which can control the way in which light interacts with them. Light reflected by a metamaterial is refracted in the ‘wrong’ way, potentially rendering objects invisible, or making them appear as something else.

Metamaterials have a wide range of potential applications, including sensing and improving military stealth technology. However, before cloaking devices can become reality on a larger scale, researchers must determine how to make the right materials at the nanoscale, and using light is now shown to be an enormous help in such nano-construction.

The technique developed by the Cambridge team involves using unfocused laser light as billions of needles, stitching gold nanoparticles together into long strings, directly in water for the first time. These strings can then be stacked into layers one on top of the other, similar to Lego bricks. The method makes it possible to produce materials in much higher quantities than can be made through current techniques.

In order to make the strings, the researchers first used barrel-shaped molecules called cucurbiturils (CBs). The CBs act like miniature spacers, enabling a very high degree of control over the spacing between the nanoparticles, locking them in place.

In order to connect them electrically, the researchers needed to build a bridge between the nanoparticles. Conventional welding techniques would not be effective, as they cause the particles to melt. “It’s about finding a way to control that bridge between the nanoparticles,” said Dr Ventsislav Valev of the University’s Cavendish Laboratory, one of the authors of the paper. “Joining a few nanoparticles together is fine, but scaling that up is challenging.”

The key to controlling the bridges lies in the cucurbiturils: the precise spacing between the nanoparticles allows much more control over the process. When the laser is focused on the strings of particles in their CB scaffolds, it produces plasmons: ripples of electrons at the surfaces of conducting metals. These skipping electrons concentrate the light energy on atoms at the surface and join them to form bridges between the nanoparticles. Using ultrafast lasers results in billions of these bridges forming in rapid succession, threading the nanoparticles into long strings, which can be monitored in real time.

“We have controlled the dimensions in a way that hasn’t been possible before,” said Dr Valev, who worked with researchers from the Department of Chemistry, the Department of Materials Science & Metallurgy, and the Donostia International Physics Center in Spain on the project. “This level of control opens up a wide range of potential practical applications.”

---

- See more at: http://www.cam.ac.uk/research/news/building-invisible-materials-with-light#sthash.HbctmqrE.dpuf

A New Approach to SETI: Targeting Alien Polluters

Humanity is on the threshold of being able to detect signs of alien life on other worlds. By studying exoplanet atmospheres, we can look for gases like oxygen and methane that only coexist if replenished by life. But those gases come from simple life forms like microbes. What about advanced civilizations? Would they leave any detectable signs?

They might, if they spew industrial pollution into the atmosphere. New research by theorists at the Harvard-Smithsonian Center for Astrophysics (CfA) shows that we could spot the fingerprints of certain pollutants under ideal conditions. This would offer a new approach in the search for extraterrestrial intelligence (SETI).

"We consider industrial pollution as a sign of intelligent life, but perhaps civilizations more advanced than us, with their own SETI programs, will consider pollution as a sign of unintelligent life since it's not smart to contaminate your own air," says Harvard student and lead author Henry Lin.

"People often refer to ETs as 'little green men,' but the ETs detectable by this method should not be labeled 'green' since they are environmentally unfriendly," adds Harvard co-author Avi Loeb.

The team, which also includes Smithsonian scientist Gonzalo Gonzalez Abad, finds that the upcoming James Webb Space Telescope (JWST) should be able to detect two kinds of chlorofluorocarbons (CFCs) -- ozone-destroying chemicals used in solvents and aerosols. They calculated that JWST could tease out the signal of CFCs if atmospheric levels were 10 times those on Earth. A particularly advanced civilization might intentionally pollute the atmosphere to high levels and globally warm a planet that is otherwise too cold for life.

There is one big caveat to this work. JWST can only detect pollutants on an Earth-like planet circling a white dwarf star, which is what remains when a star like our Sun dies. That scenario would maximize the atmospheric signal. Finding pollution on an Earth-like planet orbiting a Sun-like star would require an instrument beyond JWST -- a next-next-generation telescope.

The team notes that a white dwarf might be a better place to look for life than previously thought, since recent observations found planets in similar environments. Those planets could have survived the bloating of a dying star during its red giant phase, or have formed from the material shed during the star's death throes.

While searching for CFCs could ferret out an existing alien civilization, it also could detect the remnants of a civilization that annihilated itself. Some pollutants last for 50,000 years in Earth's atmosphere while others last only 10 years. Detecting molecules from the long-lived category but none in the short-lived category would show that the sources are gone.

"In that case, we could speculate that the aliens wised up and cleaned up their act. Or in a darker scenario, it would serve as a warning sign of the dangers of not being good stewards of our own planet," says Loeb.

This work has been accepted for publication in The Astrophysical Journal and is available online.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

article link

Scientists Make Most Precise Measurement of an Alien World's Size

Thanks to NASA's Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the radius of a planet outside our solar system. The size of the exoplanet, dubbed Kepler-93b, is now known to an uncertainty of just 74 miles (119 kilometers) on either side of the planetary body.

The findings confirm Kepler-93b as a "super-Earth" that is about one-and-a-half times the size of our planet. Although super-Earths are common in the galaxy, none exist in our solar system. Exoplanets like Kepler-93b are therefore our only laboratories to study this major class of planet.

With good limits on the sizes and masses of super-Earths, scientists can finally start to theorize about what makes up these weird worlds. Previous measurements, by the Keck Observatory in Hawaii, had put Kepler-93b's mass at about 3.8 times that of Earth. The density of Kepler-93b, derived from its mass and newly obtained radius, indicates the planet is in fact very likely made of iron and rock, like Earth.

"With Kepler and Spitzer, we've captured the most precise measurement to date of an alien planet's size, which is critical for understanding these far-off worlds," said Sarah Ballard, a NASA Carl Sagan Fellow at the University of Washington in Seattle and lead author of a paper on the findings published in the Astrophysical Journal.

"The measurement is so precise that it's literally like being able to measure the height of a six-foot tall person to within three quarters of an inch -- if that person were standing on Jupiter," said Ballard.

Kepler-93b orbits a star located about 300 light-years away, with approximately 90 percent of the sun's mass and radius. The exoplanet's orbital distance -- only about one-sixth that of Mercury's from the sun -- implies a scorching surface temperature around 1,400 degrees Fahrenheit (760 degrees Celsius). Despite its newfound similarities in composition to Earth, Kepler-93b is far too hot for life.

To make the key measurement about this toasty exoplanet's radius, the Kepler and Spitzer telescopes each watched Kepler-93b cross, or transit, the face of its star, eclipsing a tiny portion of starlight. Kepler's unflinching gaze also simultaneously tracked the dimming of the star caused by seismic waves moving within its interior. These readings encode precise information about the star's interior. The team leveraged them to narrowly gauge the star's radius, which is crucial for measuring the planetary radius.

Spitzer, meanwhile, confirmed that the exoplanet's transit looked the same in infrared light as in Kepler's visible-light observations. These corroborating data from Spitzer -- some of which were gathered in a new, precision observing mode -- ruled out the possibility that Kepler's detection of the exoplanet was bogus, or a so-called false positive.

Taken together, the data boast an error bar of just one percent of the radius of Kepler-93b. The measurements mean that the planet, estimated at about 11,700 miles (18,800 kilometers) in diameter, could be bigger or smaller by about 150 miles (240 kilometers), the approximate distance between Washington, D.C., and Philadelphia.

Spitzer racked up a total of seven transits of Kepler-93b between 2010 and 2011. Three of the transits were snapped using a "peak-up" observational technique. In 2011, Spitzer engineers repurposed the spacecraft's peak-up camera, originally used to point the telescope precisely, to control where light lands on individual pixels within Spitzer's infrared camera.

The upshot of this rejiggering: Ballard and her colleagues were able to cut in half the range of uncertainty of the Spitzer measurements of the exoplanet radius, improving the agreement between the Spitzer and Kepler measurements.

"Ballard and her team have made a major scientific advance while demonstrating the power of Spitzer's new approach to exoplanet observations," said Michael Werner, project scientist for the Spitzer Space Telescope at NASA's Jet Propulsion Laboratory, Pasadena, California.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

NASA's Ames Research Center in Moffett Field, California, is responsible for Kepler's ground system development, mission operations and science data analysis. JPL managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colorado, developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by the agency's Science Mission Directorate.

For more information about the Kepler mission, visit:

http://www.nasa.gov/kepler

For more information about Spitzer, visit:

http://spitzer.caltech.edu

http://www.nasa.gov/spitzer

article link

Astronauts to Test Free-Flying “Housekeeper” Robots

                 Image Credit: NASA

NASA Ames' Smart SPHERES, a Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) equipped with Google's Project Tango smartphone.

Image Credit: 

NASA Ames / Eric James

Aboard Orbital Sciences Corp.'s second contracted commercial resupply mission to the space station, which arrived to the orbital laboratory July 16,  NASA's Ames Research Center in Moffett Field, California, sent two Google prototype Project Tango smartphones that astronauts will attach to the SPHERES for technology demonstrations inside the space station. By connecting a smartphone to the SPHERES, it becomes "Smart SPHERES, " a more "intelligent" free-flying robot with built-in cameras to take pictures and video, sensors to help conduct inspections, powerful computing units to make calculations and Wi-Fi connections to transfer data in real time to the computers aboard the space station and at mission control in Houston.

For the first Smart SPHERES experiments in 2011, a Nexus S was launched to the station on the final flight of space shuttle Atlantis. For the upcoming experiments, the features of the Project Tango phone add new capabilities to increase the options of what researchers can do with the SPHERES platform.

In a two-phase experiment, astronauts will manually use the smartphones to collect visual data using the integrated custom 3-D sensor to generate a full 3-D model of their environment. After the map and its coordinate system are developed, a second activity will involve the smartphones attached to the SPHERES, becoming the free-flying Smart SPHERES. As the free-flying robots move around the space station from waypoint to waypoint, utilizing the 3-D map, they will provide situational awareness to crewmembers inside the station and flight controllers in mission control. These experiments allow NASA to test vision-based navigation in a very small mobile product. 

“NASA uses robots for research and mission operations; just think about the rovers on Mars or the robotic arm on the ISS or space shuttle," said Chris Provencher, manager of the Smart SPHERES project. "Inside the ISS space is limited, so it’s really exciting to see technology has advanced enough for us to demonstrate the use of small, mobile robots to enhance future exploration missions."

Ultimately it is the hope of researchers that these devices will perform housekeeping-type tasks, such as video surveys for safety and configuration audits, noise level measurements, air flow measurements, and air quality measurements, that will offset work the astronauts currently perform.

The SPHERES facility is managed under NASA's Human Exploration and Operations Mission Directorate, Advanced Exploration Systems division. The Smart SPHERES project and SPHERES facility are managed under the Intelligent Robotics Group at NASA Ames, with participation from NASA’s Johnson Space Center in Houston and NASA's Jet Propulsion Laboratory in Pasadena, California.

Credit: Maria Alberty NASA's Ames Research Center

The remarkable similarity to the spheres of science fiction, in particular the film Oblivion is noted: ed

Australian Scientists Twist Light with New Material

Scientists at The Australian National University (ANU) have uncovered the secret to twisting light at will. It is the latest step in the development of photonics, the faster, more compact and less carbon-hungry successor to electronics.

This image depicts David Powell twisting light.

Credit: ANU

A random find in the washing basket led the team to create the latest in a new breed of materials known as metamaterials. These artificial materials show extraordinary properties quite unlike natural materials.

"Our material can put a twist into light – that is, rotate its polarisation – orders of magnitude more strongly than natural materials," said lead author Mingkai Liu, a PhD student at the ANU Research School of Physics and Engineering (RSPE).

"And we can switch the effect on and off directly with light," said Mr Liu .

Electronics is estimated to account for two per cent of the global carbon footprint, a figure which photonics has the potential to reduce significantly. Already light carried by fibre optics, has replaced electricity for carrying signals over long distances. The next step is to develop photonic analogues of electronic computer chips, by actively controlling the properties of light, such as its polarisation.

The ability of a material to rotate polarisation, as in this experiment, springs from the asymmetry of a molecule. It occurs in natural minerals and substances; for example, sugar is asymmetric and so polarisation rotation can be used to measure sugar concentrations, which is useful in diabetes research.

However the remarkable properties of this artificial material might first be put to use in the budding photonics industry, suggests co-author Dr David Powell, also from RSPE.

"It's another completely new tool in the toolbox for processing light," he says. "Thin slices of these materials can replace bulky collections of lenses and mirrors. This miniaturisation could lead to the creation of more compact opto-electronic devices, such as a light-based version of the electronic transistor."

The metamaterials are formed from a pattern of tiny metal shapes, dubbed meta-atoms. To obtain optical rotation Mr Liu and his colleagues used pairs of C-shaped meta-atoms, one suspended above the other by a fine wire. When light is shined on to the pair of meta-atoms the top one rotates, making the system asymmetric.

"The high responsiveness of the system comes because it is very easy to make something hanging rotate," says Mr Liu.

"The idea came to me when I found a piece of wire in my washing one day."

The fact that the team's meta-atoms move when light shines on them adds a new dimension, he says.

"Because light affects the symmetry of our system, you can tune your material's response simply by shining a light beam on it. Tunability of a metamaterial is an important step towards building devices based on these artificial materials," he says.

###

The work is published in Nature Communications.

credit ANU

It’s go for LUX-Zeplin experiment in dark matter

From the physics labs at Yale University to the bottom of a played-out gold mine in South Dakota, a new generation of dark matter experiments is ready to commence.

The LZ water shield, currently housing the LUX experiment.

 Daniel McKinsey, a professor of physics, leads a contingent of Yale scientists working on the project.

The U.S. Department of Energy’s Office of Science and the National Science Foundation recently gave the go-ahead to LUX-Zeplin (LZ), a key experiment in the hunt for dark matter, the invisible substance that may make up a large part of the universe.

“We emerged from a very intense competition,” said McKinsey, whose ongoing LUX (Large Underground Xenon) experiment looks for dark matter with a liquid xenon detector placed 4,850 feet below the Earth’s surface. The device resides at the Sanford Underground Research Facility, in South Dakota’s Black Hills.

The new, LZ device will boost the size and effectiveness of the original LUX technology.

“We have the most sensitive detector in the world, with LUX,” McKinsey said. “LZ will be hundreds of times more sensitive. It’s gratifying to see that our approach is being validated.”

LZ is an international effort, involving scientists from 29 institutions in the United States, Portugal, Russia, and the United Kingdom. The DOE’s Lawrence Berkeley National Lab manages the experiment.

Dark matter is a scientific placeholder, of sorts. Although it can’t be seen or felt, its existence is thought to explain a number of important behaviors of the universe, including the structural integrity of galaxies.

LZ’s approach posits that dark matter may be composed of Weakly Interacting Massive Particles – known as WIMPs – which pass through ordinary matter virtually undetected. The experiment aims to spot these particles as they move through a container of dense, liquid xenon. That container will be surrounded by a tank of water, along with an array of sophisticated light sensors and other systems.

A 3D rendering of the LZ detector.

Putting the device down a mineshaft weeds out cosmic rays, McKinsey said. Gamma rays and neutrinos, however, still will be able to seep into the device. They’ll be like tiny bowling balls, careening into the liquid xenon and colliding with electrons. Those collisions will be identified and factored out.

The researchers hope that the remaining collisions, the ones involving nuclei, will identify the presence of dark matter. “It comes down to distinguishing between electron and nuclear recoils,” McKinsey said.

LZ will be a meter taller and significantly wider than its predecessor. The amount of xenon will jump from 250 kilograms to 7,000 kilograms. Such considerations become critical when you’re conducting research in a mine, according to McKinsey.

“Everything has to come down in the same cage,” he said.

As with LUX, a number of systems and components for LZ will be designed and built at Yale. For example, McKinsey said, team members in New Haven will work on calibration systems. They also will construct a system for bringing high voltage into the device’s lower grid.

The goal is to have LZ operational in 2017, while continuing work with the LUX experiment.

“We want to get moving soon,” McKinsey said. “We have new systems we want to start testing. Our activity has begun.”

Two other dark matter initiatives also earned support. Those are the SuperCDMS-SNOLAB, which will look for WIMPs, and ADMX-Gen2, which will search for axion particles.

By Jim Shelton

credit 

Congrats to Planetary Society who will Sail Again with LightSail

"We're back!" said Louis Friedman, Executive Director of The Planetary Society. “With an even more ambitious solar sail program than our last venture."

The Planetary Society today announced LightSail, a plan to sail a spacecraft on sunlight alone by the end of 2010. The new solar sail project, boosted by a one-million-dollar anonymous donation, was unveiled at an event on Capitol Hill in Washington, D.C on the 75th anniversary of the birth of Planetary Society co-founder Carl Sagan, a long-time advocate of solar sailing.

LightSail is an innovative program that will launch three separate spacecraft over the course of several years, beginning with LightSail-1, which will demonstrate that sunlight alone can propel a spacecraft in Earth orbit. LightSails 2 and 3, more ambitious still, will reach farther into space.

“We are going to merge the ultra-light technology of nanosats with the ultra-large technology of solar sails in an audacious new program,” said Friedman.

Taking advantage of the technological advances in micro- and nano-spacecraft over the past five years, The Planetary Society will build LightSail-1 with three Cubesat spacecraft. One Cubesat will form the central electronics and control module, and two additional Cubesats will house the solar sail module. Cameras, additional sensors, and a control system will be added to the basic Cubesat electronics bus.

"To get sunlight to push us through space, we need a large sail attached to a small spacecraft.Lightsail-1 fits into a volume of just three liters before the sails unfurl to fly on light. It's elegant," exclaimed Planetary Society Vice President Bill Nye the Science Guy.

LightSail seeks to create and prove solar sail technologies that in a few years can

* monitor the Sun for solar storms,
* provide stable Earth observation platforms, and
* explore our solar system without carrying heavy propellants.

Sailing on light pressure (from lasers rather than sunlight) is also the only known technology that might carry out practical interstellar flight, helping pave our way to the stars.

"Sailing on light is a pathway to the stars, but on that path are also some very important scientific and engineering applications that help us understand and protect our own planet and explore other worlds," remarked Planetary Society President Jim Bell.

Reflected light pressure, not the solar wind, propels solar sails. The push of photons against a mirror-bright surface can continuously change orbital energy and spacecraft velocity. LightSail-1will have four triangular sails, arranged in a diamond shape resembling a giant kite. Constructed of 32 square meters of mylar, LightSail-1 will be placed in an orbit over 800 kilometers above Earth, high enough to escape the drag of Earth’s uppermost atmosphere. At that altitude the spacecraft will be subject only to the force of gravity keeping it in orbit and the pressure of sunlight on its sails increasing the orbital energy.

Lightsail-2 will demonstrate a longer duration flight to higher Earth orbits. LightSail-3 will go to the Sun-Earth Libration Point, L1, where solar sails could be permanently placed as solar weather stations, monitoring the geomagnetic storms from the Sun that potentially endanger electrical grids and satellite systems around Earth.

The Planetary Society’s attempt in 2005 to launch the world's first solar sail, Cosmos 1, was scuttled when its launch vehicle, a Russian Volna rocket, failed to reach Earth orbit. But the organization’s membership never lost faith in the goal to sail on wings of light, and now, thanks to their continued support – including the million dollar private (and anonymous) donation – the new LightSail project will begin.

Sagan’s widow and collaborator, Ann Druyan – whose Cosmos Studios was the Society’s partner and principal sponsor of Cosmos 1 – serves as Chief Advisor to the current project.

Druyan commented, “Carl and I once wrote ‘We have lingered too long on the shores of the cosmic ocean. It’s time to set sail for the stars.’ We are celebrating his birthday by announcing the maiden voyages of a fleet of ships conceived to fulfill that mythic imperative. I think I know what this would have meant to him.”

James Cantrell, CEO of Strategic Space Inc, is Project Manager of LightSail-1. Stellar Exploration will build the spacecraft in San Luis Obispo, CA. Other team participants include the Cubsesat development group at California Polytechnic University, San Luis Obispo, and a team at Russia’s Space Research Institute.

credit link