Greetings all. For your consideration I offer the following - World/Moon system From Neville Jones Mon May 19 20:02:46 2008 "Diagrams, comments, thoughts, one-way tickets to the Gulag, ... toss them all into the pot and let's see what comes out." I've been kicking this idea around for a while and this invitation seems timely. First a few simplifications - The Earth's orbit is a circle; the Moon's orbit is a circle; The Moon's orbit lies in the plane of the ecliptic; the Earth/Moon barycentre is at the centre of gravity of the Earth. Next, some approximate dimensions - The Earth's orbit has a radius of 150 * 10^6 km; The Moon's orbit has a radius of 384 * 10^3 km; the Earth revolves at 360/365.25 = 0.986 deg/day; the Moon revolves at 360/27.322 = 13.2 deg/day; the Earth has an orbital speed of 30 km/s; the Moon has an orbital speed of 1.0 km/s. At full moon, the Moon has a cumulative speed of 30 + 1 = 31 km/s while at new moon it will be 30 - 1 = 29 km/s. Therefore the Moon at full moon in one day will traverse an angle of atan ( 31 km/s * 86400 s / (150 * 10^6) + (384 * 10^3) km ) = 1.020 deg while at new moon the corresponding angle will be atan ( 29 km/s * 86400 s / (150 * 10^6) - (384 * 10^3) km ) = 0.959 deg -- a difference of almost 0.061 deg/day. Plotted on the circumference of a circle of radius 10 m, this angle represents a shade under 11 mm. If we place the Moon without the Earth at a point on the Earth's orbit and hold it in a fixed position, it will continue to rotate on its axis at a rate of 13.2 deg per day. A shadow from a sun dial on its surface will move from West to East at 13.2 deg per day. Alternatively, if we place the Moon alone on the Earth's orbit but cause it to orbit the Sun in its own right, and we stop its rotation on its axis, then a shadow from the same sun dial will move from East to West at a rate of 0.986 deg per day. Restoring its rotation while retaining its revolution, we will find that the shadow will move in a West to East direction at 13.2 - 0.986 = 12.21 deg/day. Now for the interesting bit. First we restore the Earth/Moon system to normal and recall to mind the angular speed (wrt the Sun) of the Moon at full moon and at new moon where a difference of 0.061 deg/day was shown. Splitting this 50/50, we have a shadow advancing West to East at 12.21 + 0.061/2 = 12.241 deg/day at full moon and 12.21 - 0.061/2 = 12.180deg/day at new moon. Should the Universe however be centred on the Earth with the Moon and the Sun orbiting it, the Moon's radial speed will be constant and so the rate at which the shadow advances will be constant. A real test would of course need to take into account the fact that both orbits in question are in fact ellipses, that they are not in the same plane and that the orientation of the Luna orbit major axis remains fixed while its angle to the Sun is constantly varying. I'm sure there will be other things which have not occurred to me but I am also sure that -- if I have the mechanics properly sorted -- this effect is eminently measurable. That we cannot immediately rush out and do the experiment matters not -- science is in the habit of making predictions which routinely take decades or centuries to demonstrate or destroy. Finally, the Earth/Moon barycentre is not at the Earth's centre of gravity -- there is an offset of about 4700 km. While the effect is greatly reduced, it seems to me that the rate of shadow advance could, under these conditions, also be shown to differ slightly between new moon and full moon on the Earth. Paul D Get the name you always wanted with the new y7mail email address. www.yahoo7.com.au/mail