On Wed, Feb 19, 2014 at 2:38 AM, John Berry <[email protected]> wrote:
Are you arguing that this is impossible? > This is a thought experiment so it only has to be theoretically possible > to make such a measuring instrument. > > I would consider it obvious that such an instrument is possible. > I have no need to argue that it's impossible. Clarity of thought suggests that we start from something we already know about, rather than a hypothetical measurement I've never seen before. About the possibility of the instrument -- I would assume any photon would be likely to be scattered during the first reading, and then, even if it was not, the act of being retransmitted to en route to the second detector would add in an unacceptable time delay that would invalidate our measurement. According to SR, no we wouldn't. > But if what was moving was anything else including a particle moving at > almost the speed of light. > If it was anything that can possibly be understood we would. > > Right now you are using circular reasoning that seems very much like > arguments for belief in God. > I think you misunderstand. You're claiming that SR is logically inconsistent. I'm hoping you can help me to understand this and come to the same conclusion. In order to do so, I have to be convinced that you're not setting up a straw man. Right now I'm persuaded of exactly the opposite. SR claims, as an assumption, that light in a vacuum, measured in an inertial frame, will be detected to be moving at *c*, no matter the reference frame. This is an axiomatic assumption based on empirical evidence. Einstein saw evidence that the speed of light would always be measured at the same velocity in an inertial frame, and then he asked the question of what would happen if this observation was turned into a fixed point, i.e., made into an axiom. He then derived a bunch of weird stuff about length contraction, time dilation, Lorentz invariance, etc. These were conclusions that were based on the earlier assumption (and other assumptions). I'm not arguing that he was correct. I'm arguing that if we're to show that he was incorrect, we should stick to SR and not something that is different from SR. It's a question of logical reasoning, not faith. If we start talking about how time dilation and length contraction show how the speed of light will not be measured to be *c* in a vacuum traveling in an inertial frame, we've either come across a trivial logical inconsistency (unlikely, but possible I suppose), or we've misunderstood one or two applications of the basic assumptions in SR. You cannot say that R is illogical, describe R,' pick apart R' (or attempt to pick it apart), and then transfer any conclusions back to R. I'm trying to help you to help me to better understand why SR is incorrect by helping you to avoid setting up a straw man argument. I'm pessimistic that this is going to go anywhere. Eric
