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Published: Thursday 29 August, 2013

cheap shoes on sale cheap shoes on sale Could Tsarnaev have hid from infrared



This article originally appeared on Scientific American.



Late last Friday a terrible week that began with the bombing of the Boston Marathon came to a satisfying, if somber, conclusion. The last alleged perpetrator of the horrific events at the marathon and MIT was arrested after a most dangerous game of hide and seek.



Photos and videoslike these highlight just how far our detective technology has come. Specifically, Tsarneav was indentified with the aid of a FLIR forwardlooking infrared camera mounted to a police helicopter. But how does this apparent Xray vision work, and is there any way the bomber could have hid from this seemingly allseeing eye?



What You Dont See Gives You Away



Infrared IR radiation is able to make it through a lot of interference like smoke or fog or a boat tarp because it is composed of long electromagnetic waves. Take a look at theelectromagnetic spectrumand youll see that infrared has longer waves than visible light right beforeinfra, beneathred light. And as we have all seen from thermal images, it just so happens that heat throws much of its energy across the universe as infrared. In fact, if you heat something up enough, these long infrared wavelengths bunch closer together until some bleeds into the visible spectrum. This is why you can heat something up until it glows red. Keep heating it and it will glow blue, following the same spectrum. Note that most of the color thermal images have this scale reversed. This is because it is more intuitive to think of redder areas as hotter.



So when you look at an infrared image, you arent actually looking through anything. Infrared is just another kind of electromagnetic radiation that happens to make it through the material your camera is focused on. When police looked through the tarp of the boat Tsarneav was hiding in, they saw him because his bodys output of long wavelengths were making it through the boat tarp material, not some Supermanlike Xray vision.



But because seeing someone or something with infrared requires the radiation to make it through whatever is between it and the camera, there are bound to be materials that effectively block out IR. Slippin cheap shoes on sale g behind a mat cheap shoes on sale erial like that makes you invisible to a camera that sees the invisible.



Nowhere to Run, One Place to Hide



Glass, specifically the kind of glass you have in your home, is designed to block infrared radiation. Keeping in all that heat is important for keeping heating bills down. Point an IR camera at most glass and it will seriously distort, if not completely block, any IR radiation coming from behind it. Youll get the relative surface temperature of the glass and thats about it.



You can prove this pretty easily. First notice the differencein this videobetween a car with a window up and a window down in terms of what you can see the camera is the same FLIR technology used to catch the Boston bomber. Next find a device that puts out nearinfrared radiation shorter wavelengths close to visible light, like your TV remote. The signal it sends is still invisible to you, but I bet you can change the channel through a window. The shorter wavelengths emitted by your remote make it through glass while the FLIR cant make it past the passenger window. This is partly why your car gets so unholy hot in the summer; the glass traps the IR radiation!



If Tsarneav wanted to hide from infrared cameras, he couldnt have picked a worse spot.



The ideal place to shield your heat signature would be in a glass greenhouse. Surrounded by glass that isdesigned to reflect heaton all sides, you would be invisible to IR cameras and Predator. Visible light comes in but IR cant get out. In fact, this is partly why humans are able to live on this planet. Light from the Sun penetrates our atmosphere, heats up the surface, and then that heat attempts to leave. Greenhouse gases reflect the IR down back at Earth, keeping the heat inthe greenhouse effect. By masking yourself in glass and hiding in an envelop of greenhouse gases, a helicopter like the one used in Watertown, MA would be blind.



Unless he knew some critical physics, the alleged Boston bomber could have never escaped infrared detection. Of course, knowing how to shield yourself from the seeing eye in the sky has one key disadvantage: putting yourself behind glass puts you squarely back in the visible spectrum. But dont hate it for being beautiful; its got substance, too. The forest boasts 8 wilderness areas, 2,500 miles of trail, 1,900 miles of winding service system roads, and 12 ski resorts should your snow shredders fit the trunk space. If ice isnt your thing: take the tirefriendly Flat Tops Trail Scenic Byway 82 miles connecting the towns of Meeker and Yampa, half of which is unpaved for you road rebels. Try driving the Ridge and Valley Scenic Byway, which saw Civil War battles fought. If the tall peaks make your engine tremble, opt for the relatively flat Oconee National Forest, which offers smaller hills and an easy trail to the ghost town of Scull Shoals. Scaredycats can opt for Johns Mountain Overlook, which leads to twin waterfalls for the sensitive sightseer in you. Travel 20 miles west of Dolly Sods among cheap shoes on sale the busiest in the East to find the Canaan Backcountry for more quiet and peace. Those willing to leave the car for a bit and foot it would be remiss to neglect dayhiking the White Rim Rocks, Table Rock Overlook, or the rim at Blackwater River Gorge. Rogers NRA via Hurricane Creek Road, North CarolinaMost know it as the highest country theyll see from North Carolina to New Hampshire. What they may not know? Car campers can get the same grand experience for less hassle. Drop the 50pound backpacks and take the highway to the high country by stopping anywhere on the twisting hence the name Hurricane Road for access to a 15mile loop that boasts the best of the grassy balds. Its the road less travelled, and the high one, at that. For a weekend getaway of the coastal variety and quieter version of the Florida Keys thats no less luxe, stick your head in the sand and ocean, if snorkelings your thing at any of Long Keys 60 sites. Canoes and kayaks are aplenty, as are the hot showers and electric power source amenities. Think of it as the getaway from the typical getaway. With the Colorado River still within view of this cliffedge site, Crazy Jug is a carside campers refuge from the troops of tourists. Find easy access to the Bill Hall Trail less than a mile from camp, and descend to get a peek at the volcanic Mt. Trumbull. With a worldwide print and digital audience of more than five million people, fourteen local language editions, and a major new



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