Known physics defeated by simple puzzle?
in [Relativity]
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From: Sue... on 6 Apr 2010 18:19 On Apr 6, 6:13 pm, Edward Green <spamspamsp...(a)netzero.com> wrote: > On Apr 5, 4:47 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > I'm happy to make concessions, but I have to be able to ask questions > > and get meaningful answers. The ladder in the barn is a prime example. > > I'm told "the ladder contracts to fit in the barn". And I ask "so a > > person riding the ladder would see the barn expand", and the answer > > comes back "no, no, the person riding the ladder would see the barn > > *contract*". So I say, "well clearly in the latter case the ladder > > cannot possibly fit with both doors shut, so it must be a visual > > effect". "No, no" comes the reply, "the ladder *really* does fit > > according to a person standing in the barn, and it *really* doesn't > > fit according to the person riding the ladder". And I say, "well, it > > can't do both at once", and the reply that is merely asserted in > > response is "well, it does!". > > > And that sums up thousands of words in probably hundreds of posts > > exchanged between me and a quite a few posters on the ladder and barn > > paradox. It always comes back to a plain assertion that "this is how > > it works", but there is no attempt to explain *why*, or any attempt to > > show how a mere visual explanation would not suffice for some or all > > of the observed effects. > > It's definitely not "optical" or "visual". Relativistic length > contraction and time dilation is an effect left over when all > corrections for the finite speed of light have been removed. > > Part of resolving the paradox involves the finite speed of light also, > but in a different way. Say the ladder fits from the viewpoint... > ahem... "frame of reference" of the barn. What is going on in the > frame of the ladder? Well, this short little barn is approaching at > nearly the speed of light. The barn is too short to contain the > ladder. However, the barn is going so fast that light speed impulses > traveling down the ladder from the impact with the first closed barn > door cannot reach the other end of the ladder before it passes through > the second, open, barn door, which then closes. Viola, the ladder is > in the barn. > > Now, if you wish to repeat the experiment with the barn doors left > open, so that the ladder is not destroyed, we must have recourse to > the differing time scales in the two frames, and how they interact > with distance. The observer on the barn concludes that there is a > moment when the ladder is completely contained in the barn, whereas > the observer on the ladder, with his differing time scale, concludes > there was no such moment. Ditto for a mixed version of the experiment, > where we close the barn doors with a flourish, and reopen them before > the ladder collides with them: the observer on the barn thinks both > doors were closed simultaneously at least for a moment, whereas the > observer on the ladder sees no such thing -- he sees the leading door > of the shortened barn opened before he hits it, and the trailing door > close after all his ladder has passed through it. > > Hope this helps. So you are saying the principle of relativity is a myth? Sue...
From: Edward Green on 6 Apr 2010 18:25 On Apr 5, 7:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > It contracts to fit the barn in the rest frame of the barn, which is > > why the ladder makes no marks on the barn doors when the doors are > > shut at the same time. In the rest frame of the ladder, the ladder > > does not contract and indeed does not fit inside the barn at all. In > > the rest frame of the ladder, the reason why there are no marks on the > > barn doors when they are shut is that they were not shut at the same > > time in this frame. > > This logic is easily defeated Paul, because if we contracted the > ladder's length *just* enough so that it marked the door in the barn > frame (in other words, the ladder has contracted just enough to manage > an interference fit with both doors shut), then this cannot be > accounted for in the ladder frame (because, in the ladder frame, if > the ladder is *even larger* relative to the barn than when it started, > then the ladder could not possibly mark the doors in the same way). Sure it could. The "interference fit" corresponds to opening the leading door just as the ladder impacts it, and closing the trailing door just in time to impact the ladder. But in the time of the ladder's frame, these events are no longer simultaneous. Have you actually looked at the simple form of the Lorentz transformation? Notice how time and distance become mixed up: maybe this is important. Don't become as cranky as some people suspect me of being because I won't buy exclusively into an orthodox semantics concerning a thought experiment whose facts are not in doubt.
From: Edward Green on 6 Apr 2010 18:33 On Apr 5, 10:00 pm, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > It is a measured effect (provided you could accelerate a pole to those > speeds and put some instruments on it). The relevant events are the > aperture/closure of the barn doors, which are as real as they can be. > On the barn frame of reference both doors could be safely closed, > simultaneously, for 1 nanosecond, with the pole inside the barn and > not touching any of the doors (those are two events, which in the > frame of reference of the barn are simultaneous). On the pole frame of > reference, these same two events do happen (as they should since any > two physical events happening on one frame have also to be observed in > any other frame), but this time they are not simultaneous (one door > closes-opens before the other door). Concisely and well said.
From: Sue... on 6 Apr 2010 18:36 On Apr 6, 6:25 pm, Edward Green <spamspamsp...(a)netzero.com> wrote: > On Apr 5, 7:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > > It contracts to fit the barn in the rest frame of the barn, which is > > > why the ladder makes no marks on the barn doors when the doors are > > > shut at the same time. In the rest frame of the ladder, the ladder > > > does not contract and indeed does not fit inside the barn at all. In > > > the rest frame of the ladder, the reason why there are no marks on the > > > barn doors when they are shut is that they were not shut at the same > > > time in this frame. > > > This logic is easily defeated Paul, because if we contracted the > > ladder's length *just* enough so that it marked the door in the barn > > frame (in other words, the ladder has contracted just enough to manage > > an interference fit with both doors shut), then this cannot be > > accounted for in the ladder frame (because, in the ladder frame, if > > the ladder is *even larger* relative to the barn than when it started, > > then the ladder could not possibly mark the doors in the same way). > > Sure it could. The "interference fit" corresponds to opening the > leading door just as the ladder impacts it, and closing the trailing > door just in time to impact the ladder. But in the time of the > ladder's frame, these events are no longer simultaneous. Have you > actually looked at the simple form of the Lorentz transformation? There seems to be a general consensus that LET predicts such absurdities: http://en.wikipedia.org/wiki/Lorentz_ether_theory That is why is was superseded by Einstein's relativity and there is no ambiguity about what is real. << the four-dimensional space-time continuum of the theory of relativity, in its most essential formal properties, shows a pronounced relationship to the three-dimensional continuum of Euclidean geometrical space. In order to give due prominence to this relationship, however, we must replace the usual time co-ordinate t by an imaginary magnitude sqrt(-1) ct proportional to it. Under these conditions, the natural laws satisfying the demands of the (special) theory of relativity assume mathematical forms, in which the time co-ordinate plays exactly the same rôle as the three space co-ordinates. >> http://www.bartleby.com/173/17.html > Notice how time and distance become mixed up: maybe this is important. > > Don't become as cranky as some people suspect me of being because I > won't buy exclusively into an orthodox semantics concerning a thought > experiment whose facts are not in doubt. The imaginary operator always precedes the semantic operator. Sue...
From: Edward Green on 6 Apr 2010 18:47
On Apr 5, 11:07 pm, Ste <ste_ro...(a)hotmail.com> wrote: > I still fail to see any plausible explanation for the difference in > simultaneity, except that it is due to a careful placement of the > observer and a differential in the delay of propagation. The laws of physics are locally Lorentz invariant. That means they are invariant in form when the coordinates undergo a transformation of the Lorentz form. This is also known as a change in reference frame. The form of the transformation involves mixing time and distance. This is the origin of the change in simultaneity. The identity of form of the laws of physics under the transformation accounts for each observer thinking _his_ coordinates are the natural ones. All other results follow. > Incidentally, do the doors shut at different times depending on > *where* you sit on the ladder? No. |