Hi everyone, I am not a physicist, so I've been looking at "layman's terms" type sources for the answers to these questions, but I'm afraid they've just left me with more questions. I'll frame the questions around the concept of solar sails: 1. Solar sails are reflective -- since some of the momentum of light is being transferred to the solar sail, I assume the reflected light has a lower energy than the incoming light. Is the reflected light a lower frequency? Or lower amplitude (brightness?)? 2. According to this source: http://science.howstuffworks.com/solar-sail.htm/printable" [Broken], you could power a solar sail with an on-board laser... that doesn't make sense to me. Maybe I'm just thinking too "Newtonian" about this, but wouldn't the emitting laser impart a force equal and opposite to force of the light bouncing off the solar sail? Isn't this why we don't see large fans on sail boats to create wind on calm days? 3. If solar sails were absolutely black, would they still work (though less efficiently)? I'm ignoring the fact that they would heat up, and then radiate their own energy for the purposes of this question. I'm having trouble wrapping my head around how reflecting the light results in more momentum transferred than absorbing it completely. I thank you in advance for your help here.