The beams of sun might have appeared only hot so far but now it will be regarded as forceful too. Basically, light emitted from sun is also a kind of radiation and it is a common knowledge that radiation of every kind exerts pressure. Now this theory has come into practice, although in a nascent stage right now.
The scientist community knew as early as in 1920s that a spaceship can be propelled only by the force of sunbeams but at that time it was just on paper. After almost ninety years in May 2010, Japan’s Aerospace Exploration Agency launched, for first time in aeronautics history, a spacecraft which only uses solar propulsion as its primary source of driving force.
The spacecraft, named as ‘Interplanetary Kite-craft Accelerated by Radiation of the Sun’, reached Venus, in December, after five months, as was expected. A polyimide sail was used for spacecraft’s movement. The main feature of the sail is that of it being only 7.5 microns thick despite being 14 meters long. Its highly reflective surface, made up of high quality polymer, doubles the thrust given by sun beams to almost .112 grams force. Encouraged by this experiment, a team of scientists at Rochester Institute of Technology, New York has demonstrated another force light can exert.
They took a transparent rod, semicircular at cross section and even thinner than a human hair and then they directed a beam at it. As the photons of beams flew through it, the pressure which they exert on rod, first rotated it till it found equilibrium and then pushed it. It’s exactly the same way the flow of air round an aerofoil creates ‘lift’.
Though this effect is on a very small scale, such a ‘light foil’ can have applications not only in the near-vacuum of space but even on Earth. “The advantage of these rods is that you can use a lot of them together.” Explained Ortwin Hess, Professor in Physics and Leverhulme Chair in Metamaterials at Imperial College London.
So what is the expected benefit from these experiments? The pressure light exerts is at a very small scale, and so this pressure can be used in two contexts, first is space because there is total vaccum and therefore there will be no resistance to it’s force and secondly, in nanotechnology, where moving things have very little mass. It is hoped that in future the energy of light will be used to drive micro machines and bring huge changes in our lives.
Via: Guardian
