Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 8 Apr 2010 22:09 On 8 Apr, 15:10, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 10:32 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > It's awfully difficult to misinterpret the numerical value of a > measurement and whether it agrees with the numerical value of another > measurement. No, because if I say relative to me A is moving at 10kmh and B is moving at 20kmh, and you say that relative to you A is moving at 20kmh, and B moving at 30kmh, then despite the numerical difference of speeds we both agree about the movement of A relative to B.
From: Ste on 8 Apr 2010 22:12 On 8 Apr, 15:18, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 10:43 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 8 Apr, 02:47, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Apr 7, 8:40 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > I doubt that after writing "It cannot fit and not fit at the same > > > > > > > time" you really understand this gedanken at all. > > > > > > > It depends what you mean by "understand". If you mean "have grasped > > > > > > its tenets, and can reason the conclusion from those tenets", then I > > > > > > understand it totally. If you mean "accept that length contraction > > > > > > really occurs", then the answer is no. And I suspect at this point the > > > > > > real problem is not my lack of understanding of the paradox, but your > > > > > > lack of understanding of what I mean by "real". > > > > > > Real is what can be verified by a measurement. > > > > > No it isn't. This is a fundamental difference between us. I dare say > > > > there are lots of things that cannot be verified by measurement, but > > > > only by inference from other measurements. > > > > Not that are of scientific interest, no. > > > It certainly *ought* to be of scientific interest. > > It ought to be of scientific interest that there are lots of things > that cannot be verified by experiment but inferred from other > measurements? No, I don't think so. But I do think so. It's a bit like how I infer the moon exists even when I'm not observing it, even though by definition I can't be sure what is happening when I'm not observing. > That would apply to angels and demons. No, thank you. As I've said before, I think science would do better to simply assert it's naturalistic ideology, rather than pretending that the demarcation between science and religion lies in the method.
From: Inertial on 8 Apr 2010 22:13 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:a0b2160b-e6e4-4637-b9d1-5a257e07e72c(a)x20g2000yqb.googlegroups.com... > On 8 Apr, 15:02, PD <thedraperfam...(a)gmail.com> wrote: >> On Apr 7, 10:21 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> > > Remember the ladder is moving relative to the barn. >> > > How does one determine that the ladder is contained completely >> > > inside, >> > > exactly? >> >> > By shutting the doors at the same time, of course. >> >> Yes, indeed, this is a crucial ingredient. And of course if the doors >> were not shut at the same time, then we would not say that the first >> object fit inside the second object, would we, even though otherwise >> the observations would be the same? That is, if the front of the >> ladder were inside the barn (having verified that it passed through >> one but not the other door) when one door was shut, and the back of >> the ladder were inside the barn (by the same verification) when the >> other door was shut, this would be no indication that the ladder fit >> inside the barn, right? Especially if the doors were not shut at the >> same time. > > Indeed. The question, really, is not whether the ladder fits inside > when the doors are actually shut, but whether it *would* fit if they > *were* shut. yes > As I say, I don't think we need to discuss extensively > what "fitting" means We do . .because you seem to think it is a frame-indepednent concept. it isn't > - but for completeness, it simply means whether > the full extent of the ladder could be at once contained within the > confines of the barn. 'At once' is what makes it frame dependent. So the answer depends on which frame of reference is dertmining whether or not the doors are closed 'at once' >> So, jumping to the chase, if in one reference frame, it is established >> that the doors were shut at the same time, then the definition of >> "fitting" inside the barn would have been met, and the ladder would >> have fit inside the barn in that frame. If in another reference frame, >> it is established that the doors were not shut at the same time, then >> the definition of "fitting" inside the barn would not have been met, >> and the ladder would not have fit inside the barn in that frame. So, >> you see, it is entirely possible -- and indeed we would be forced to >> this conclusion -- that the ladder fits in the barn (by virtue of your >> own definition) in one frame and does not fit in the barn in another >> frame, provided that we can establish that the timing of the doors >> being shut depends on the frame. > > Yes, but this is a contradiction in reality, No .. it isn't. It only contradict how you incorrectly think that reality must work. There's a difference. > so the only other > explanation is that perhaps it *appears* to do this, but does not > actually do so. no . .the other correct explanation is the reality does NOT work as you think it does. > And of course, my money would be that nothing changes > real length at all, If you mean frame-invariant rest-length (or proper length) .. then you are correct. It does not change. But that is NOT what is being talked about when saying whetehr a pole firts between the barn doors when they are both closed at the same time. > and that the appearance of this is an illusion Its not an illusion. > that can be explained somehow in terms of the behaviour of the > electromagnetic interaction (possibly combined with a > misinterpretation of what relativity actually describes, and an > ignorance of the mechanisms underlying the effects of relativity). Nope .. no EM interaction required .. It is not an optical illusion. You *really* need to understand what SR says, and what is meant by such terms as 'length' and 'simultaneous'.
From: Peter Webb on 8 Apr 2010 22:14 Yes, but this is a contradiction in reality, so the only other explanation is that perhaps it *appears* to do this, but does not actually do so. And of course, my money would be that nothing changes real length at all, and that the appearance of this is an illusion that can be explained somehow in terms of the behaviour of the electromagnetic interaction (possibly combined with a misinterpretation of what relativity actually describes, and an ignorance of the mechanisms underlying the effects of relativity). __________________________________________ And if anybody is going to offer an explanation based upon "a misinterpretation of what relativity actually describes, and an ignorance of the mechanisms underlying the effects of relativity", you certainly seem well qualified for the job.
From: Inertial on 8 Apr 2010 22:19
"Ste" <ste_rose0(a)hotmail.com> wrote in message news:eb581e80-73ee-4f1b-b86a-729c49128d65(a)8g2000yqz.googlegroups.com... > On 8 Apr, 15:10, PD <thedraperfam...(a)gmail.com> wrote: >> On Apr 7, 10:32 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> It's awfully difficult to misinterpret the numerical value of a >> measurement and whether it agrees with the numerical value of another >> measurement. > > No, because if I say relative to me A is moving at 10kmh and B is > moving at 20kmh, and you say that relative to you A is moving at > 20kmh, and B moving at 30kmh, then despite the numerical difference of > speeds we both agree about the movement of A relative to B. You can both calculate what A's movement is relative to B and agree on that. Ignoring SR just for now, and just using the Galillean/Newtonian model that you seem to think is valid in cases when it is not ... That does NOT mean that A has the same velocity in all frames. And so, by your definition, A's velocity isn't real. That does NOT mean that A has the same velocity in all frames. And so, by your definition, B's velocity isn't real. However, the difference between A' not-real velocity and B's not-real velocity IS real. Similarly, the difference in their momentums is also real. However, the difference in their kinetic energies is not real. It really (sic) would be better if you dropped this confusing use of 'real', and just used 'frame independent' or 'invariant' instead. Though I know you do enjoy the word games that ensure, it is not helpful. |