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Electromagnetic radiation

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Original author: 
Liv Siddall

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It’s the work that everyone’s talking about, Richard Mosse’s infrared film shot in the heart of Congo that was shown this year at the Venice Biennale in the Irish pavilion. In this short documentary produce by frieze, Richard explains the ideas behind the film and the history behind the method itself. It turns out that infrared film, which picks up chlorophyl from only the healthiest living plants, was produced in the 1940s by the military to help them see enemies hiding out in the bushes.

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Original author: 
John Timmer

FirasMT

In the past few years, there have been a regular series of announcements about devices that cloak something in space. These typically bend light around the cloak so that it comes out behind the object looking as if it had never shifted at all. In contrast, there's just been a single description of a temporal cloaking device, something that hides an event in time. The device works because in some media different frequencies of light move at different speeds. With the right combination of frequency shifts, it's possible to create and then re-seal a break in a light beam.

But that particular cloak could only create breaks in the light beam that lasted picoseconds. Basically, you couldn't hide all that much using it. Now, researchers have taken the same general approach and used it to hide signals in a beam of light sent through an optical fiber. When the cloak is in operation, the signals largely disappear. In this case the cloak can hide nearly half of the total bandwidth of the light, resulting in a hidden transmission rate of 12.7 Gigabits per second.

The work started with the Talbot effect in mind, in which a diffraction grating causes repeated images of the grating to appear at set distances away from it. The cloaking device relies on the converse of this. At other distances, the light intensity drops to zero. The key trick is to convert the Talbot effect from something that happens in space to something that happens in time.

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MrSeb writes "Electrical engineers and material scientists at MIT have created a fiber-borne laser that could be woven to form a flexible display that could project different 3D images in any number of directions, to any number of viewers. MIT's fiber is similar to standard telecoms fiber, but it has a tiny droplet of fluid embedded in the core. When laser light hits the fluid, it scatters, effectively creating a 360-degree laser beam. The core is then surrounded by layers of liquid crystal, which can be controlled like 'pixels,' allowing the laser light to escape from specific points anywhere along the length of the fiber. This means that you could have a display that shows one picture on the 'front' and another on the 'back' — or different, glasses-free 3D images for everyone sitting in front and behind. In the short term, the laser fiber is more likely to have a significant application in photodynamic therapy, an area of medicine where drugs are activated using light. Photodynamic therapy is one of the only ways to treat cancer in a relatively non-invasive and non-toxic manner. MIT's laser could be threaded into almost any part of the body, where the ability to produce pixels of laser light at any point along its length would make it a highly accurate device."


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xmas2003 writes "Several months ago, I posted to Slashdot about being able to see ultraviolet light after cataract surgery. While a lot of the discussion whimsically discussed the best way for 'Captain UV' or 'UltraMan' to use this 'super-power,' there were some people who were skeptical or (incorrectly) said this is Tetrachromatic vision. I've subsequently done more testing using an Oriel Instruments MS257 Monochromator and was able to see color down to 350nm — below the usual ~400nm limit of the visual spectrum. It's also easily demonstrable with a pair of 400nm and 365nm UV flashlights. Some readers who also have UV vision commented this can be quite annoying at black-lit Disney Rides, Halloween Haunted Houses, etc. Fortunately for me, it's just an interesting oddity so far. Along those lines, some interesting related stories about using UV vision during World War II and Star Gazing. Finally, many/most people end up getting vision debilitating cataracts, so my experience having a Crystalens implanted after cataract surgery may be informative."


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maisel-hs_1.jpg© David Maisel, from History's Shadow

Photographer David Maisel collaborated with major art museums to create a series of stunning photos of x-rays of antique statues, sculptures and fragile vessels. The title of the series is History's Shadow, and the results are immediately compelling as they draw you in through multiple milky layers of translucent materials that could never be seen with the naked eye.

Thanks to the miracle of x-rays, we're able to see all of the surface features (front, back and sides, all at once), as well as the inner areas that display some pentimento-like traces of the artists' hands plus the pins, nails, staples and struts that support these beautiful old works of art.

Maisel's photos are beautifully eerie, ghost-like, and almost alive. It is as if we can visually see someone's thought process, suspended and preserved, from hundreds of years ago.

maisel-hs_6.jpg© David Maisel, from History's Shadow

Be sure to view the work in our high-resolution slide show, and read David's insightful text about this project.

maisel-hs_14.jpg© David Maisel, from History's Shadow

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The Senate just drove a stake into the Navy’s high-tech heart. The directed energy and electromagnetic weapons intended to protect the surface ships of the future? Terminated.

The Free Electron Laser and the Electromagnetic Railgun are experimental weapons that the Navy hope will one day burn missiles careening toward their ships out of the sky and fire bullets at hypersonic speeds at targets thousands of miles away. Neither will be ready until at least the 2020s, the Navy estimates. But the Senate Armed Services Committee has a better delivery date in mind: never.

The committee approved its version of the fiscal 2012 defense authorization bill on Friday, priced to move at $664.5 billion, some $6.4 billion less than what the Obama administration wanted. The bill “terminates” the Free Electron Laser and the railgun, a summary released by the committee gleefully reports.

“The determination was that the Free Electron Laser has the highest technical risk in terms of being ultimately able to field on a ship, so we thought the Navy could better concentrate on other laser programs,” explains Rick DeBobes, the chief of staff for the committee. “With the Electromagnetic Railgun, the committee felt the technical challenges to developing and fielding the weapon would be daunting, particularly [related to] the power required and the barrel of the gun having limited life.”

Both weapons are apples in the eye of the Office of Naval Research, the mad scientists of the Navy. “We’re fast approaching the limits of our ability to hit maneuvering pieces of metal in the sky with other maneuvering pieces of metal,” its leader, Rear Adm. Nevin Carr, told me in February. The answer, he thinks, is hypersonics and directed energy weapons, hastening “the end of the dominance of the missile,” Adm. Gary Roughead, the top officer in the Navy, told me last month. With China developing carrier-killer missiles and smaller missiles proliferating widely, both weapons would allow the Navy to blunt the missile threat and attack adversaries from vast distances.

And both have recently experienced technical milestones that made researchers squeal with glee.

In December, the Navy corralled reporters to Dahlgren, Virginia, to watch a railgun the size of a schoolbus fire a 23-pound bullet using no moving parts — just 33 megajoules of energy, a world record. (A prototype of a ship-ready railgun is pictured above.)

And this winter, the Free Electron Laser, the most powerful and sophisticated laser there is, boasted two big advances within a month. In January, its 14-kilowatt prototype passed tests that injected enough energy into it to get it up to a megawatt’s worth of death ray — a “remarkable breakthrough,” nine months ahead of schedule, the Office of Naval Research crowed. The next month, its testers at the Jefferson Lab in Newport News added even more power. Researchers think it could be far more than a weapon: it might act as a super-sensor, and Yale scientists use it to hunt for cosmic energy.

Shipboard power is the question mark surrounding both weapons. The laser and the railgun require diverting power from a ship’s generators in order to fire. The Navy’s waved that away, saying that its onboard generators — especially the superpowerful ones in development — can handle the megawattage necessary, and the Free Electron Laser’s guts are shaped like a racetrack to “recycle” some of the energy injected into it. But both plans rely on the power efficiency of ships that aren’t built yet.

Neither comes cheap, either. The Navy’s spent some $211 million since 2005 developing the railgun. Its milestones with the Free Electron Laser — in development in some form since the ’90s — led it to ask Congress for $60 million in annual directed-energy research funds, most of which go to the superlaser. Needless to say, a Senate panel facing a huge budget crunch was unsympathetic.

The Office of Naval Research didn’t respond by press time. The process of passing a defense budget making it through no fewer than four committees and two floor votes, so it’s not like these programs cease to exist. But unless the Navy makes a big push for its futuristic weapons, both of them will die on the drawing board.

Photo: Spencer Ackerman

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