Invisibility cloaks: Will we ever really have them?
By Jason Palmer Science and technology reporter, BBC News
12 November 2012



You've seen the films, you've read the popular science stories. It's time to ask: when will you have your invisibility cloak?

Hold your horses. It's looking like a great many things inspired by cloaking science will come to pass before then.

Behind most cloaking ideas is the use of metamaterials - materials whose properties are purposefully designed, defined not by chemistry but by the materials' size, shape and structure.

They are already starting to crop up in consumer technology, and could find widespread use in applications ranging from computers to concert halls.

It is a simple idea whose scientific foundations are dizzyingly complex.

At its simplest, explains John Pendry of Imperial College London, "you just want to grab hold of the light coming from an object, guide light around the hidden thing, and then return it to the path it was going on originally - and that's easier said than done."

Another alternative is to find out what a given object will do to incident light beams and create a cloak that does the exact opposite - that's the aim of what are known as plasmonic metamaterials.

Luckily, there are many ways to pull off the invisibility trick. The metamaterials approach seems to be the most promising, but a number of what might be called optical tricks have also cropped up.

... much more at link
http://www.bbc.co.uk/news/science-environment-19661503

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Do not go gentle into that good night.
___________ Rage, rage against the dying of the light

Other ways to disappear


optical camouflage, keio university

• Optical camouflage technology: A modified background image is projected onto a cloak of retro-reflective material (the kind used to make projector screens); the wearer becomes invisible to anyone standing at the projection source
  
• The "mirage effect": Electric current is passed through submerged carbon nanotubes to create very high local temperatures, this causes light to bounce off them, hiding objects behind
  
• Adaptive heat cloaking: A camera records background temperatures, these are displayed by sheets of hexagonal pixels which change temperature very quickly, camouflaging even moving vehicles from heat-sensitive cameras
  
• Calcite crystal prism: Calcite crystals send the two polarisations of light in different directions. By gluing prism-shaped crystals together in a specific geometry, polarised light can be directed around small objects, effectively cloaking them

_________________
Do not go gentle into that good night.
___________ Rage, rage against the dying of the light

Interesting

We had a strange disappearing effect here at the back of my house. If we turn off the patio lights but just use the flood lights then as people walked along the back they would appear to disappear just before they came to a turn. We tried it over and over with all size people and they all went poof! Hahaa

How cool! I love that photo of the man in front of the soda.


That must be a trip, Packy!

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