Human-scale invisibility cloak created by father and son team for $150

Human-scale invisibility cloak created by father and son team for $150

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Two magicians physicists at the University of Rochester in New York have created an invisibility cloak capable of hiding large objects, such as humans, buses, or satellites, from visible light. Surprisingly, rather than relying on exotic and hard-to-manufacture materials, this invisibility cloak is fashioned out of conventional mirrors. This isn’t theoretical, like some of the other invisibility cloaks we’ve covered — you could build this cloak today from off-the-shelf parts and hide yourself from view.

Before you get too excited, though, this invisibility cloak — created by John Howell at the University of Rochester and his 14-year-old son Benjamin — is unidirectional. This means that it only cloaks objects that are being observed from a single, fixed position; if you move more than a few degrees to the side, or above, you can clearly see the object that’s being cloaked. With that said, though, if you’re far enough away from the object — say, if you’re cloaking an orbiting satellite or military spy plane — then the very narrow field of view means that unidirectional cloaking works just fine. It should work reasonably well at medium range, too; at a range of a few hundred meters, a human (or tank) could be fairly well hidden by this invisibility cloak.

The unidirectional invisibility is fashioned out of two right-angle mirrors. As you can see in the diagram to the right, this arrangement of mirrors bounces the light around an object, so that the light striking your eye comes from the scene behind the object. The invisibility isn’t perfect, but due to the finicky nature of electromagnetic radiation we’ll probably never have perfect invisibility. That’s basically all there is to it.

If this sounds vaguely familiar, it’s because it’s the same setup that magicians have been using for years to vanish people and objects. “The point we wish to emphasize is not the novelty,” Howell & Son admit in their research paper, “but the ease of scaling to nearly arbitrary size.” Here they are referring to the fact their mirror-based invisibility cloak can be scaled up indefinitely, while other invisibility cloaks — such as those based on metamaterials — currently operate on the centimeter scale or smaller.

While this current approach with flat, rectangular mirrors placed at right angles will always be limited to unidirectional cloaking, exotic mirrors and interesting angles might allow for multi-directional and -dimensional invisibility. A cloak with spherical symmetry could perhaps be constructed out of retroreflecting spheres – spheres that reflect almost all of the light back to its source with minimal scattering, such as a cat’s eyes. In recent years, there have been numerous theoretical studies and a few practical demonstrations of mirrored invisibility that move us towards methods of cloaking that would be useful in everyday life. For now, though, the prospect of satellites that are almost invisible from Earth is fairly chilling…

ET deals: slim Dell XPS 18 all-in-one mobile desktop

As Intel’s ULV processors have improved over the years and dropped in price, they are now suitable for more than just ultraportable laptops. Dell took the Ivy Bridge chips and built an oversized tablet form factor around them. The XPS 18 combines an 18.4-inch ultra-slim slate design running Windows 8.

This nets you a full PC experience, including a spacious 1080p screen, but with the mobile touch experience of a tablet. A built-in battery gets you up to five hours of run time away from an outlet, while the whole chassis weighs in at five pounds. It comes with all the built-in features you need to get around, including Wireless-N, Bluetooth, Ethernet, USB 3.0, media card reader, and an HD webcam. You get a wireless keyboard and mouse included for docking at the home, and Dell even throws in on-site service and accidental damage coverage for no charge.

If this kind of computing experience is appealing, you can snag one right now with a very rare coupon code that takes $50 off the base dual-core model and $100 off the Core i3 and higher versions. This lets you grab the XPS 18 starting at just $849.99 with free shipping.