BLAMING SPECIAL RELATIVITY?
in [Physics]
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From: Danny Milano on 14 Jul 2008 14:17 On Jul 14, 11:51 pm, Sam Wormley <sworml...(a)mchsi.com> wrote: > Danny Milano wrote: > > > Spacetime has continuous structure. > > What "structure" would that be? > > Quantum has "now you see it, > > > now you don't" characteristic. How does spacetime behave in > > the quantum realm. You can't have "now you see it, now you > > don't spacetime". Because it's no longer our normal spacetime. > > What's the difference between "normal spacetime" and "not normal > spacetime"? Normal spacetime has a manifold. Not normal spacetime has no manifold. Planck scale reality may have no manifold. D. > > > String theory covers it by saying at the planck scale, there is the > > string and the scale where quantum and spacetime are in > > contrast. > > I have yet to see "string theory" covering anything.
From: Greg Hansen on 14 Jul 2008 18:28 hhc314(a)yahoo.com wrote: > First of all, Einstein emphasised that the Special Theory of > Relatively only applied to to observations made in UNACCLERATED > REFERANCE FRAMES. This is a common misconception. But it's the postulates of special relativity that are tied to unaccelerated reference frames. The speed of light is invariant in an unaccelerated reference frame, and the principle of relativity is applied to unaccelerated reference frames. But special relativity certainly can handle accelerated reference frames. The process is basically one of boosting in succession from one inertial frame to another and taking a limit, and we assume that the acceleration itself doesn't introduce any novel physics. In other words, take the derivative with respect to time of the Lorentz transformations as many times as you like. There are many articles in the literature about the accelerating rocket, the rotating disk, identically accelerated twins, and so on. Accelerated reference frames, like the uniformly accelerating rocket, introduce many gravity-like features, like a clock in the nose ticking faster than a clock in the tail. But the gravity of Earth can't be modeled by a uniformly accelerating rocket because the gravity of Earth has a different magnitude and different direction at different points in space. General relativity adds a relation between intrinsic curvature and the stress-energy tensor, and that has many interesting results. Except for that, the two theories are not actually radically different-- once you have your metric, and you define an observer frame (which could be accelerated), you can work out your trajectories. But special relativity texts give you all the easy problems, so students wind up using the pseudo-unitary metric for everything and wondering why they should bother with the complication of a metric at all.
From: theauthor on 14 Jul 2008 20:41 On Sun, 13 Jul 2008 06:33:00 -0500, Greg Hansen <greg> wrote: > >Here's a case in point. Another is that if you consider what a >approaching and receding trains "look like", the approaching train would >appear shorter because of the difference in signal propagation times >from the front of the train and the back, and a receding train would >longer. No, you got that the wrong way round. Differential signal propagation delays cause the approaching train to look longer, and the receding train to look shorter. The correct behaviour (for SR and for other theories) is analysed and illustrated in Chapter 7: "Apparent length-changes in moving objects", and there's a full-page diagram on pp.72 of the approaching and receding trains. See? The book's useful! ;)
From: Eric Gisse on 14 Jul 2008 22:03 On Jul 14, 4:41 pm, theauthor wrote: > On Sun, 13 Jul 2008 06:33:00 -0500, Greg Hansen <greg> wrote: > > >Here's a case in point. Another is that if you consider what a > >approaching and receding trains "look like", the approaching train would > >appear shorter because of the difference in signal propagation times > >from the front of the train and the back, and a receding train would > >longer. > > No, you got that the wrong way round. Differential signal propagation > delays cause the approaching train to look longer, and the receding > train to look shorter. > > The correct behaviour (for SR and for other theories) is analysed and > illustrated in Chapter 7: "Apparent length-changes in moving objects", > and there's a full-page diagram on pp.72 of the approaching and > receding trains. > > See? The book's useful! ;) Yet you post under a name that is impossible to search for under Google.
From: N:dlzc D:aol T:com (dlzc) on 14 Jul 2008 22:15
"Eric Gisse" <jowr.pi(a)gmail.com> wrote in message news:93f18b28-e08c-4c52-b9bb-8ab0e8cf6d6c(a)2g2000hsn.googlegroups.com... .... > Yet you post under a name that is impossible to > search for under Google. Eric Baird. Even bought an "untraceable" domain to house his "book". I prefer: http://www.motionmountain.net/ David A. Smith |