Hope this is the right forum. Rather daunting task to pick the right forum when you don't understand what differentiates each topic... Anyhow, I've been reading Feynman "QED The Strange Theory of Light and Matter" (lectures). Actually, I've read it about 3 times, cover to cover. I get some of it, but I have two questions I hope maybe someone here could shed some light on. That wasn't a pun. With regards to partial reflection, Feynman states "The situation today is, we haven't go a good model to explain partial reflection by two surfaces; we just calculate the probablity that a particular photomultiplier will be hit by a photon relfected from a sheet of glass." ok, so Newton figured maybe light knew what kind of surface it was hitting, and whether it was the only surface, and therfore gave the partial reflection you would expect (or canceled out reflection completely). Well that theory is circumspect. I don't think science believes that today. But Feynman talked about shooting a laser through 50 meters of glass and getting the 0 to 16% relfection at the exepected intervals, based on the thickness of glass...... so can I use this for Faster Than Light communication? (i hope not). Or, in these excessive tests with extremly thick glass, does it takes longer and long for the initial reflection to occur? That seems weird. If there wasn't a delay (tied to the thickness of glass) before reflection, then given a 10 lightyear think piece of glass, I could communicate faster than light by shaving off one end of the glass, which would instantaniously change the partial reflection given at the face of the glass. And that just doesn't seem right. well, that was my first question. My second question has simply to do with the notion of "arrows" in QED. The so-called stopwatch hands, which spins faster or slower based on the color of light. While I like the abstraction, and it certainly helps in understanding whats going on, I now would like to know what it actually corrosponds to in the physical world. I'm guessing it can be tied to the frequency of light (because in his lectures he mentions that the 'blue' light stopwatch is faster than the 'red' light stopwatch). Thanks all, -Frank O'Connor "A fire-breathing dragon lives in my garage."