Solar sail

Solar sails (also called light sails or photon sails) are a form of spacecraft propulsion which uses large mirrors, driven by radiation pressure exerted by sunlight. A useful analogy may be a sailing boat; the light exerting a force on the mirrors is akin to a sail being blown by the wind. High-energy laser beams could be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing.