What would happen if you switched on a laser pointer in space?
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, it's absolutely tiny, but you will get pushed backwards very, very, slowly. In fact, they're 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, it's reflected back again and that means it's changed it's direction and your mirror will get pushed away. The force is a tiny micro-newtons (I mean mili-newtons), but because you don't 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 you're going a long way, far quicker than you could.
Chris - Because over time, it will build up, and build up, and build up with no losses because there's almost nothing to hit you and slow you down again.
Dave - It's been suggested it's 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.