On 23 Sep 2011, at 20:46, Stephen A. Lawrence wrote: > > On 11-09-23 03:30 PM, Dr Josef Karthauser wrote: >> >> >> From first principles if one starts with the notion that everyone should see >> light as travelling at the same speed, then a simple derivation naturally >> leads to the Lorenz contraction from which all of special relativity is >> constructed. Then we go on to see that that length contraction and time >> dilation must occur; a natural consequence of the contraction equation. And, >> we have to ask the question "how can a body have infinite mass"? Naturally >> we give up and say that it can't and so it can't happen. > > Not exactly. > > The actual conclusion is not that no body can go as fast as C. (Obviously, > it can -- photons do.) > > In fact, the conclusion is also not that no body can go faster than C. (In > fact, it's SR which gave rise to the idea of tachyons.) > > Rather, the conclusion is that information cannot be transmitted faster than > C in any arbitrary reference frame, because to do so leads to contradictions. > Nature may or may not abhor a vacuum but I'm pretty darn sure Nature abhors > a contradiction. > > See, for instance: > > http://www.physicsinsights.org/ccentipede.html > > Note, however, that FTL communication would entail no contradictions if it > were restricted to a single, distinguished inertial frame. The problems > arise when we allow FTL communication in an arbitrary frame. With such a > free for all, signals relayed from one frame to another can arrive before > they leave.
Hey Stephen, Ok, I agree. I was a bit careless with that paragraph; however, I'm still not sure how a hard conclusion about the maximum velocity of bodies can be derived from that approach. The link you used included by example of the kinds of contradiction that can occur if you allow superluminal communication starts with the phrase "Relativity forbids travel at speeds faster than light," which goes against your previous paragraphs. They obviously think that SR shows that, as do most people. Also, in my story that I tried to tell later in my email, I did not require information exchange between the relative frames. Rather, explicitly I spoke about two frames becoming "Lorentz disconnected", and I tried to suggest that the transition that would occur as the change in relative velocity between the two frames passed through the singularity in the Lorentz transformation was not excluded by nature and that our thinking around the discontinuity was a limitation of our imaginations not the Universe. I'd be interested in your thoughts about that, if you've got a moment to consider them. Yours, Joe
