Cloaking device developed, for fish

13 June 2013
Posted by Dominic Ford.

The dream of invisibility goes back to at least the Greeks whose god of the underworld, Hades is supposed to have had a helmet of invisibility.

But this week scientists at the Nanyan Technological University in Singapore, unveiled a video of a goldfish and cat disappearing and reappearing behind a new 'invisibility cloak' they'd developed. If you haven't seen it yet you can find a link to the video below but in the meantime here's the Quickfire Science...

At the moment objects like tanks can only be disguised, using cameras to project the view behind the tank onto screens covering the other side. This was seen on a car in the James Bond movie, Die Another Day.

However this technology only works from one perspective - the angle the camera is facing - so if you spotted the tank from a different angle, it would distort the illusion.

But in 2006, British Researcher Sir John Pendry came up with a way of bending light around an object to create a 'cloak', which would make it invisible to the naked eye.

However when light waves are bent around an object they have to travel further than the light unaffected by the cloak. This means the bent light arrives slightly later than it should so the image isn't perfect.

To correct this, the bent light waves have to appear to move faster than the unaffected light travelling in air, which is impossible with natural materials.

Cloaks like this have been built successfully with artificial 'metamaterials', made with carefully designed structures smaller than the wavelength of light. But they've only been able to hide objects from view in microwaves rather than visible light.

To disguise large objects in visible light, the team in Singapore decided to see how well they could manage with conventional materials, not worrying about whether the light was delayed.

They used prisms of glass in a hexagon or square which refract the light through one another around the object - so even if your pet moves inside the prisms it looks like it has disappeared!

This can still only be seen from a maximum of six angles but the hope is that they will be able to increase this by changing the layout of the prisms.

They have managed to hide goldfish and even a cat in a real life environment and hope it could be used for both surveillance and entertainment.

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