I was watching a show on the science channel called "Alien Encounters". Well in one of them they showed a ship that looked as if it was propelling itself by firing a laser at it's solar sail. Now I am pretty sure that from what I understand about physics, that would not be possible. Correct if I am wrong but when a laser is fired, the laser beam (electromagnetic waves) carry momentum, now since the laser beam carry's momentum then a reverse momentum must be created on the ship that it is firing from, only in the opposite direction. So now if you have a solar sail on that very same ship and the laser beam is absorbed or reflected from that solar sail, then the laser beam momentum is transferred to the solar sail. So now your momentum from firing the laser and the momentum absorbed from the solar sail should cancel out and thus your ship should not move at all. Is this correct? Don't atoms move the opposite direction that a photon is emitted from?