DStahl: I'd like to draw the discussion together under one heading, and invite Tim Thompson, Agora Basta, David Hall, JS Princeton, Wiley, and all the others who have engaged the topic to explore it some more here.

I didn't want y'all to feel ignored, but it seems I have little to offer in addition. I do remember deriving Heisenberg's uncertainty principle in a general form, though not in the manner alluded to by Chen. So I poked around and found the proof in the mathpages collection ("Fourier Transforms and Uncertainty"). This proves the theorem Chen mentioned, as well as providing the connection to Heisenberg's uncertainty. I was unaware of this until Chen mentioned it, very spiffy.

cable: we can detect the presence/absence of a pure CW

I too have pondered this notion, but two things come to mind. First, a pure CW signal does not constitute information in the sense that Chen is talking about. The Fourier transform of a pure CW is a delta function, which only conveys the "information" you already mentioned, that the CW exists.

Second, and perhaps most interesting, is that all real CW signals have to turn on. You can postulate in a mathematical model, the instantaneous transition from nothing to CW. But in the real world, that can't happen. Any real transmitter will ring as it sets up the CW signal, and that ringing constitutes the kind of modulation that Chen is talking about.

This also leads to AgoraBasta's suggestion, "as abrupt a jerk as possible". Even the most abrupt of jerks will be accompanied by ringing fore & aft, which constitutes the modulation Chen describes.

Is Walker-Dual unexplained? I should think not. The results seem to be in line with theoretical expectations. The real problem is that most people don't properly understand what the theoretical expectations are.

Is gravity superluminal? It does not appear to be so over any meaningful measure of distance. I like Carlip's explanation ("Aberration and the Speed of Gravity", Physics Letters A 267: 81-87, March 13, 2000), and note (as does Carlip) that there are astronomical observations relevant to the near-field speed of gravity in binary pulsar timing, which shows that the speed of gravity even there is within a few percent of the speed of light.

I see nothing here that challenges standard physics, though the topic is quite interesting nonetheless.