Stephen A. Lawrence wrote (on the vortex list): > I just added a page on the Sagnac effect to my little relativity site. > For once I actually attempted to keep the math under control; there's > nothing messier than a Lorentz transform on the page. If you find the > Sagnac effect confusing, or if you've been puzzled by the websites that > claim it's inexplicable in relativity theory, you might find it interesting: > > http://www.physicsinsights.org/sagnac_1.html > > Anyhow, 'nuff spam for now; this has very little to do with energy... >
Your page is well written and your graphics are informative, however your neo-Newtonian account of a light signal on a rotating disk struck me as problematic. You write: "Consider an observer riding on the rim of the disk. If he measures the velocity of the signals as they go by, he'll find that they're both going the same speed, regardless of which direction they're going in. Classically, in the fixed frame of reference of the laboratory, we'd have the counterclockwise signal velocity = v + k, and the counterclockwise signal velocity would be = v - k," >From the standpoint of absolute space it does not follow that the observer riding on the disk would measure the same velocity for the light signal. This can only happen if the rotating cable can drag absolute space along with it, which is of course impossible by the principle of absolute of space. So if we treat absolute space as absolutely immobile rather than as a kind of semi-mobile aether of 19th century physics, the true counterclockwise signal velocity is k + v and the true clockwise signal velocity is k - v. In other words, as light interacts with a mechanical reference frame its speed changes to respect the absoluteness of space. This explains the Sagnac effect without relativity theory. Indeed, it I think by treating relative light motion as a subtractive procedure instead of additive procedure we can explain all relativistic effects without Lorentz transformations. Thus the Galileo transform (V) + (-v) is good for material bodies, but light obeys the transform (c) - (-v). Harry
