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curiousuburb
Antimatter Man
 
Join Date: May 2004
Location: that interweb thing
 
2010-12-08, 08:19

Light provides lift to a 'Lightfoil'

Quote:
Originally Posted by BBC

Time-lapse images show the progression of the "lightfoil"
Just as air causes lift on the wings of an aeroplane, light can do the same trick, researchers have said.

The effect, first shown in simulations, was proven by showing it in action on tiny glass rods.

Like the aerofoil concept of wings, the approach, published in Nature Photonics, works by making use of the radiation pressure of light.

The results are of interest for steering "solar sails", a spacecraft propulsion based on the same force.

Each photon - or packet of light - carries its own momentum, and this "lightfoil" works by gathering the momentum of light as it passes through a material.

This radiation pressure has been considered as a fuel-free source of propulsion for long-distance space missions; a "solar sail" gathering up the momentum of the Sun's rays can get a spacecraft up to a significant fraction of the speed of light.

But until now, no one thought to use the pressure in an analogue of an aerofoil, said Grover Swarzlander of the Rochester Institute of Technology (RIT).


*Light coming in from the left passes through the glass "lightfoil"
*Some passes straight through the back surface, while some is reflected and exits through the bottom (white arrows)
*This change in the light particles' momentum is balanced by another force: lift (blue arrow)
"The surprising thing from our model shows it has different positions of rotational equilibrium, so it will roll to a given position, stay there, and continue to undergo lift," Dr Swarzlander said.

The team went on to design tiny glass rods, less than a hair's breadth across, to prove the principle.

The rods were floated in water, through which a laser was shone. They behaved just as the simulations had predicted.

Given the widely known radiation pressure effect, the discovery of optical lift may be most surprising in that no one had come to this conclusion before.

... continues ...
Optical Travel (with sunglasses required).
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