The only thing that you know regarding > aberration is that something is moving. It most certainly isn't a > demonstrated fact that the Earth rotates. I didn't say it was. What I said is that it demonstrates the fact that the earth MOVES - i.e. it goes in an orbit round the sun. Look at it again Alan. Stevem said "The only thing that you know regarding aberration is that something is moving." That means rotating and orbiting. I am getting some very confused returns (confused people) from Google on aberration, so I'm not commenting till I see it in action. However I still think everything is relative, so the effect can be caused by either movement. More important to me at the moment is doppler and the speed of light in different inertial frames, special relativity n all that. Any body know what the speed of light is through glass or water? Pity we cant post graphics. Fowler shows a whammy for thinking about. me anyway. Phil.