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prescription glasses two types of screening machines that let passengers skip the undressing part. A machine undresses you by using either X rays or millimeter radio waves. The backscatter X ray technique is the one getting the most publicity at the moment. In this machine, imagine a beam of low power X rays, similar to a laser beam in dimensions, scanning across your body, left to right, top to bottom. The machine uses detectors to see how many of the X rays scatter off each point of your body instead of being absorbed. Certain materials like clothing don't cause much scatter at all. Skin has a certain characteristic scattering effect, as do different metals and certain explosives. The machine paints an image of the backscattered results point by point, and an agent looking at the image can see metals, ceramics and explosives attached to a passenger's body.The image that comes back is basically an image of a naked human body it is a strip search without the stripping. Plus it is fast and efficient.So what is the problem? There are three actually. First, many people don't like the idea of having photos of their naked bodies taken by any means. In addition, there are a number of anecdotal stories about attractive women being more likely to be scanned, which doesn't help in that regard. Second, because X rays involve ionizing radiation, many perhaps most people have health concerns. All you have to do is look at public reaction to new nuclear power plants and the public acceptance of sunscreens to understand these concerns.The third problem is the perception that it is much ado about nothing that the TSA represents "security theater" rather than actual security. This idea first took root because the TSA has not traditionally been very proactive. A terrorist had to bring explosives in the soles of his shoes before the TSA scanned shoes.A terrorist had to bring in innocent looking liquids to mix a bomb in the air before liquids were prohibited. Printer cartridges were not banned until explosives showed up in printer cartridges.In the case of backscatter scanners, the TSA actually is being proactive. It is plugging a security hole before anyone exploits it. In doing this the TSA has met