I can see the future - and it's INVISIBLE. Want a magical cloak to make you disappear like Harry Potter?

I can see the future - and it's INVISIBLE. Want a magical cloak to make you disappear like Harry Potter?
November 21, 2010
By Michael Brooks
Mail Online

The studios where the Harry Potter movies are made - Hertfordshire's Leavesden Film Studios - are only about 20 miles from Imperial College's research laboratories in South Kensington, London.

Which makes it all the more intriguing that Imperial researchers are developing invisibility cloaks that are not a million miles away from the one Harry Potter uses to dash around Hogwarts unseen.

We have all dreamed of what might be possible if we could hide ourselves with an invisibility cloak. No wonder that invisibility is a staple of science fiction. H. G. Wells's The Invisible Man uses a chemical to make light pass right through him. In Star Trek, the Klingons use technology to 'cloak' their spaceship.
Harry Potter and the Sorcerer's Stone

Just wizard: Daniel Radcliffe, right, as Harry Potter in his invisibility cloak which he uses to dash around Hogwarts unseen

The ability to vanish has been useful to writers of magical fiction, too.

In The Lord Of The Rings the elves supply Frodo and his companions with magic cloaks so they can blend into the background.

Given the popularity of fictional invisibility cloaks, perhaps it's not surprising that scientists are striving to bring them into the real world.

For Professor Ulf Leonhardt of the University of St Andrews it's not just an idle dream, either. This distinguished scientist has received funding from The Royal Society to look into the possibilities.

Unsurprisingly, the people who are keenest on this are the military. They have been experimenting with putting cameras on one side of a tank, then relaying the pictures to giant screens mounted on the opposite side of the vehicle. The result is that you don't see the tank, just whatever is behind it.

However, this 'camouflage' doesn't work very well yet. Cuttlefish camouflage themselves effortlessly by changing the colour of their skin to match the background, but disguising a tank takes a lot of energy to keep all the images updated.

And there is another problem. The standard thermal-imaging devices - such as night-vision goggles or heat-seeking missiles - would easily spot a tank cloaked in this kind of technology.

A more promising idea is to make light flow around an object in the way that water flows around a rock in a stream. Generally, we bend the path of light by using mirrors and lenses. Here, the bending is caused by the different speeds at which light, which is composed of interacting electric and magnetic fields, travels through glass and air.

In 2000, Professor Sir John Pendry of Imperial College built a new version-of the glass lens. Prof Pendry's 'metamaterials' can steer electromagnetic fields in any direction, which is why he now gives talks entitled A Cloak Of Invisibility: Harry Potter Does Electromagnetism. In theory, he says, you could wear a coat made from the right metamaterial and the light hitting your back would bend around you and be redirected in front of you.

It is not yet possible to bend visible light with these materials. The process only works at the higher frequencies of microwave radiation.

But one notable hope has come from Chinese scientists.

J.K. Rowling described Harry Potter's invisibility cloak as 'fluid and silvery', but she probably wasn't thinking the scientists would copy her.

Last year, however, researchers in Shanghai worked out that a fabric made of silver-plated balls would have the right properties to bend visible light. There are, however, a couple of obstacles to clear.

First, the balls would have to be so small that 1,000 of them could fit into the diameter of a human hair. And second, they would only hold together in the presence of a very strong magnetic field.

There is still hope for invisibility, though. Last week, Professor Martin McCall and researchers at Imperial College unveiled a new idea.

Prof McCall has devised a way to halt the light's progress through the air. It means you could stop the light from your body reaching those around you. It would be as if you could press 'pause' before people see you do something, then pressing 'play' after you have finished.

Prof McCall said: 'I would say we might be able to do something like this within decades.'

However, he explained a 'poor man's version' that could be built today. It would work for images being transmitted along optical fibres connecting a camera to a monitoring screen. The idea is based on the fact that light travels through the fibres at a speed that depends on the light's brightness.

If you want to be undetected by closed-circuit TV as you crack a safe, for example, you inject a bright pulse of light directly into the fibres. This speeds up the light already going to the screen monitoring the camera, and creates a 'void' behind it.

So you crack the safe, get out of the vault and inject another pulse of bright light, speeding up the light in the fibres again to the point where it overtakes and overwrites the light carrying the picture of you cracking the safe.

However, current technology would create a window of only five nanoseconds for nefarious activities, and that would require transmitting the light down six miles of optical fibre.

When it comes to invisibility, we're not quite there yet. But Prof Leonhardt is optimistic: 'With one good idea, the situation could change dramatically.'

Michael Brooks is a consultant for New Scientist and the author of 13 Things That Don't Make Sense: The Most Intriguing Scientific Mysteries Of Our Time (Profile)

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