Allan Ruell asked:
If a laser pointer was floating in space and not moving in any direction, would the laser pointer move if the light was switched on? Maybe even a nano meter or movement? Has this been tested?
We ask Dave Ansel for the answer to Allan's question...
Dave - You certainly can. In fact, itís absolutely tiny, but you will get pushed backwards very, very, slowly. In fact, theyíre planning to use the same principle to sail around the solar system. So, if you build yourself a very, very, very large mirror and then the sunlight shines on it, then the light is coming towards it in one direction, itís reflected back again and that means itís changed itís direction and your mirror will get pushed away. The force is a tiny micro-newtons (I mean mili-newtons), but because you donít need to carry fuel to do that you can keep your rocket engine going continuously as you fly round the solar system. It means you can actually travel round the solar system, especially if youíre going a long way, far quicker than you couldÖ
Chris - Because over time, it will build up, and build up, and build up with no losses because thereís almost nothing to hit you and slow you down again.
Dave - Itís been suggested itís one of the ways you could get to another solar system would be to have one of these solar sails and a very, very, very large laser. Point at the solar sail and then sail on it all the way out to another star.
Light has momentum, and momentum is conserved, so the pointer would move backwards. You can indeed measure "radiation pressure" when a light beam strikes an object. alancalverd, Tue, 8th Dec 2015
There is a fault in the question was floating in space and not moving in any direction from release there is nothing to stop it moving it will already be in motion the test would have to be a specific vector with the light facing the direction the laser pointer was travelling and then maybe we could see if turning the light on had any effect on velocity.
A Solar Sail is a promising way of using light pressure to move or position spacecraft in the inner solar system.
let's put some numbers.