Known physics defeated by simple puzzle?
in [Relativity]
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From: Sue... on 5 Apr 2010 23:46 On Apr 5, 11:03 pm, Ste <ste_ro...(a)hotmail.com> wrote: [...[ =============== > > Because of the obviousness of the concept. A thing cannot fit and at > the same time not fit, because there is a logical contradiction in the > meaning of those words. You mean like a bullet can't travel 300m/s in all inertial reference frames but also be dependent on the velocity of the gun. That would be a huge contradiction. Eh? Maybe one contradiction can cancel another. Ya see, the light they used back in Einstein's time moved like bullets. So rather than invent light that moved the way the experiments showed light moving, they invented poles that shrink and barns that stretch. I guess that isn't too high a price to pay if power over Father-Time might be part of the bargain. Who could resist? Today, we just use light that moves the way light moves, Time-dependent Maxwell's equations http://farside.ph.utexas.edu/teaching/em/lectures/node41.html Its a good job too with all the power moving off poles to underground and barns getting as scarce as family farmers. There is barely enough time to read the tabloids much less a good novel. BTW Would you happen to know what year the The Time Machine by H. G. Wells was published? ;-) Sue... http://www.quackwatch.org/01QuackeryRelatedTopics/pseudo.html
From: paparios on 6 Apr 2010 00:24 On 5 abr, 23:07, Ste <ste_ro...(a)hotmail.com> wrote: > On 6 Apr, 03:00, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > > > On 5 abr, 21:25, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 6 Apr, 01:38, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > > > On 5 abr, 19:33, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > On 5 Apr, 21:59, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > > > > > On 5 abr, 16:47, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > On 5 Apr, 17:37, PD <thedraperfam...(a)gmail.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. > > > > > > > There are plenty of places where this so called "paradox" is > > > > > > explained. For instance,http://hyperphysics.phy-astr.gsu.edu/HBASE/Relativ/polebarn.html > > > > > > > The relevant part is that the fact that two events are simultaneous in > > > > > > one frame of reference does not imply that they are simultaneous as > > > > > > seen by an observer moving at a relativistic speed with respect to > > > > > > that frame. > > > > > > As far as I'm concerned Miguel, I already understand the paradox. Even > > > > > the page you reference says quite clearly: > > > > > > "From the pole point of view, the front gate closes just as the back > > > > > of the pole enters. The surprising result is that the back gate is > > > > > seen to close earlier from the pole framework, before the front of the > > > > > pole reaches it. The gate closings are not simultaneous, and they > > > > > permit the pole to pass through without hitting either gate." > > > > > > As it says, the simple explanation is that the gates don't close at > > > > > the same time according to the pole, and hence the pole sails straight > > > > > through. > > > > > That is totally correct. It means the paradox is not a paradox at all, > > > > since events that are simultaneous on one frame of reference (the > > > > barn) are not simultaneous on the other frame of reference (the one of > > > > the pole). Piece of cake.... > > > > Indeed, except that the lack of simultaneity here is a *visual* > > > effect. And that's always where the monacles fall into the drinking > > > glasses. > > > 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). > > 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. > Like the train and embankment gedanken, which is itself quite related to this gedanken, assumptions are few and logical. Events are clearly defined. If in one frame of reference the pole does not touch any of the doors, then in all frames of references you have to observe the same behavior. If that is not the case, then you would observe on some frames of reference some huge explosions (like the one produced by a pole at close to the light speed crushing a door, which can be mesured on the order of megatons), which can not be according to SR postulates. Relativity of simultaneity clearly preserves, in both frames, that those events are consistent, that is the doors never touch the pole. > Incidentally, do the doors shut at different times depending on > *where* you sit on the ladder? I don't know which is the part of the ladder here. Miguel Rios
From: Inertial on 6 Apr 2010 00:35 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:1260da05-1d23-40ed-84ba-d4bfa5c5751a(a)g11g2000yqe.googlegroups.com... > On Apr 5, 11:03 pm, Ste <ste_ro...(a)hotmail.com> wrote: > [...[ > > =============== >> >> Because of the obviousness of the concept. A thing cannot fit and at >> the same time not fit, because there is a logical contradiction in the >> meaning of those words. > My god ..Sue is finally on topic > You mean like a bullet can't travel 300m/s in all > inertial reference frames but also be dependent on the > velocity of the gun. That would be a huge contradiction. Eh? > > Maybe one contradiction can cancel another. > Ya see, the light they used back in Einstein's time > moved like bullets. > > So rather than invent light that > moved the way the experiments showed light moving, Light shows both behaviors .. like particles and like waves > they invented poles that shrink and barns that > stretch. Heheheh > I guess that isn't too high a price to > pay if power over Father-Time might be part > of the bargain. Who could resist? > > Today, we just use light that moves the way > light moves, And still have the same predicted results from SR. SR doesn't care HOW light moves .. only that its speed is c in all inertial frames > Time-dependent Maxwell's equations > http://farside.ph.utexas.edu/teaching/em/lectures/node41.html > > Its a good job too with all the > power moving off poles to underground and > barns getting as scarce as family farmers. There is > barely enough time to read the tabloids much less > a good novel. > > BTW Would you happen to know what year the > The Time Machine by H. G. Wells was published? > > ;-) > > Sue... > > http://www.quackwatch.org/01QuackeryRelatedTopics/pseudo.html >
From: Inertial on 6 Apr 2010 00:54 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:8ea63a4c-3de5-4a19-be0b-8c06f920016f(a)z7g2000yqb.googlegroups.com... > On 6 Apr, 01:13, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:a7d6645c-1261-4fc7-8528-69ff1cb56e33(a)v20g2000yqv.googlegroups.com... >> >> > On 5 Apr, 01:38, "Inertial" <relativ...(a)rest.com> wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> > Incidentally, this book (which was a link from Wikipedia) confirms >> >> > my >> >> > statement that GR is how the paradox was apparently resolved (at >> >> > least >> >> > by Einstein and a few others): >> >> >http://books.google.com/books?id=vuTXBPvswOwC&pg=PA165#v=onepage&q=&f... >> >> >> You CAN use GR .. which is a superset of SR. But SR 'solves' it as >> >> well >> >> > As I say, that's not how I understand it, >> >> That is your problem. You need to learn. Not flaunt your ignorance. > > Lol. I'm all for "flaunting". Yeup :) >> > and the written evidence >> > elsewhere (for example, in the link I've just provided) suggests that >> > even Einstein clearly felt that GR was necessary to explain it. >> >> But it is NOT necessary. Einstein even gave it as an example in his 1905 >> paper (though not with actual twins .. with moving clocks) >> >> > At the >> > very least, you can see that I'm subject to contradictory evidence >> > here, >> >> No contrary evidence. >> >> > and you can understand why I don't take your statement here at >> > face value. >> >> Do you need links to the many SR solutions to the twins paradox? > > The only SR "solution" I've seen to the twins paradox is the one about > "changing frames", There are several ways of showing it. > but it's divorced from reality No .. it is perfectly real > and therefore > repugnant to me. Your repugnance with physics doesn't make it wrong > And obviously, I don't want a purely mathematical > explanation either. You don't even want a physics one. > I want an explanation that involves words and > meaningful concepts (or possibly pictures that represent real > objects). You have to take what you can get. If you don't like the way explanations are presented, that doesn't make them wrong, nor does it invalidate the physics. >> >> >> > but >> >> >> > as I understand it, you need GR to account for acceleration (in >> >> >> > other >> >> >> > words, it's outside the scope of this discussion). >> >> >> >> Wrong .. you've had that told to you many times. SR handles >> >> >> acceleration >> >> >> just fine >> >> >> > As I say, the information I have suggests that GR is necessary to >> >> > account for the (absolute) acceleration, >> >> >> That is wrong >> >> >> > whereas SR treats >> >> > acceleration merely as a change of relative velocity >> >> >> It is a change in velocity >> >> > Yes, but do you mean a relative change of velocity or (shall we say) >> > an "absolute" change of velocity? >> >> There is no difference > > There is in the sense that I mean, where a change of relative velocity > can be accomplished without any acceleration (or "impulse" as I think > we previously agreed to describe it). That can't happen >> > Remember, relative velocity can >> > change without absolute acceleration. >> >> No > > Yes. I mean "impulse" btw. Acceleration, by definition, is change in velocity. >> > Indeed, a bullet that flies past >> > your ear undergoes a dramatic change of relative velocity to you as it >> > passes (it approaches and then recedes), >> >> No .. it doesn't > > I would argue that it does, And you'd lose. It has the same velocity the whole time (unless you include slowing due to air-resistance, and acceleration due to gravity .. but I don't think that is what you meant) > if you make reference only to the bullet > and the ear. Yeup .. no change > How would you explain, say, the change in Doppler > shifting unless there was a change of relative velocity when something > passes you? Because it depends on the speed at which something approached or recedes. > Anyway, I suppose it's an aside. Yes .. but as an example of how something can change velocity without acceleration it fails. >> > Clearly relative velocities can change with or without an >> > application of force >> >> No > > I mean "without an application of force to both objects". Then how can they change velocity? >> >> >> >> The ladder really does fit inside the barn. >> >> >> >> > But then it must fit inside the barn from *all* frames, >> >> >> >> Why? >> >> >> > Because "fitting" and "not fitting" are two mutually exclusive >> >> > states. >> >> >> You haven't answered the question >> >> > I think I have. I've insisted that the two states are mutually >> > exclusive, and I've elaborated on it below. >> >> You still haven't answered why 'fitting' must be absolute > > Because of the obviousness of the concept. Sorry .. not good enough. > A thing cannot fit and at > the same time not fit, yes it can.. just as it can be travelling at 100km/hr and 50 km/hr at the same time. > because there is a logical contradiction in the > meaning of those words. Nope. > And nor can the state be subjective for each > observer, It isn't .. it is OBJECTIVE > otherwise that isn't materialism (and it isn't causal > either). Or to repeat my earlier analogy, you can't hit a person over > the head with a hammer, and merely daze him *at the same time as* > cracking his skull wide open. That's right .. you can't. But that is no a valid analogy. >> >> >> It doesn't have the same speed in all frames. It doesn't have the >> >> >> same momentum in all frames. It doesn't have the same kinetic >> >> >> energy >> >> >> in >> >> >> all >> >> >> frames. Why must it have the same length? >> >> >> > Because the notion of "speed", "energy" and "momentum" are all >> >> > inherently relative concepts. >> >> >> As are length and duration >> >> > I don't see how length can be inherently relative (although its >> > appearance certainly can be, as I illustrated in a previous post). >> >> Because it is a frame dependent measurement. >> >> It is is your problem if you don't see how frame dependent measurements >> are >> frame dependent. > > I personally think it's just a visual effect - Then you are personally wrong > that is, a consequence > of how of how the source and receiver interact electromagnetically. Nope > I > can understand frame dependence - I just don't see how you can call > the resulting observation "real". That's because you are totally wrong about what the effect is. >> > You can't say "it >> > fits according to some observers", >> >> Yes you can. Just like you can say a train whistle has different pitches >> for different observers > > But I don't say that, do I? Then you are out of touch with reality > I say the train whistle has an inherent > pitch, It doesn't. There is no such thing. > which then translates in different ways into a apparent > received pitch. All pitch is apparent. > Remember I've just been discussing this at length with > Peter Webb earlier in the thread. And you're still wrong. >> > because that is absurd >> >> Its not .. its physics. It is not physics fault if you find it absurd > > I don't find "physics" absurd. I find certain people absurd. I find you absurd, by having the audacity to think nature should work only in a way that makes sense to you >> > as saying >> > "he was merely dazed according to some observers". >> >> That is not equivalent > > Why isn't it? If "kinetic energy" is "relative", It is > then why, in your > reasoning, can he not suffer differing degrees of injury depending on > how you observe it? Because the injury depends on the kinetic energy relative to his head > Because that's basically the sort of argument > you're making with this length contraction. No .. it isn't. >> >> > The same is true of this ladder problem. If the ladder contracts, >> >> > then >> >> > it will fit in the barn, and if it doesn't contract then it won't >> >> > fit >> >> > - but it cannot contract at the same time as not contracting, or fit >> >> > at the same time as not fitting. >> >> >> Wrong >> >> >> > However, it can *appear* to do so by careful timing of the doors and >> >> > careful placement of the observer, and so naturally I'm saying to >> >> > myself "this must be what you mean". >> >> >> No .. it really fits. You really need to understand the scenario >> >> before >> >> drawing conclusions from it >> >> > I do understand the scenario. It is explained by the apparent timing >> > of the doors. >> >> The timing of the doors is PART of the scenario. It states that they >> shut >> (briefly) at the same time according to any observer (or observers) at >> rest >> wrt the barn. The pole fits between them when they are simultaneously >> shut > > Yes, but that depends on simultaneous *according to whom*, It is frame dependent .. but everyone at rest in a given frame will agree on what is simultansous > and because > (as Paul Draper has noticed) I use a different definition of > "simultaneous" to "most of the physics community". Then that is your problem. And you should NOT use a word like 'simultaneous' that has a different meaning to you than it does to the rest of the world (not just physics). Pick a different word (or phrase) >> >> >> > including the >> >> >> > rest frame of the ladder. And I know that is not what SR >> >> >> > predicts. >> >> >> >> But you are insisting that only things that are frame independent >> >> >> are >> >> >> real >> >> >> (which rules out a large amount of what we measure and work with in >> >> >> physics). >> >> >> > No, I'm insisting that observations/changes can have a "real" basis, >> >> > or an "apparent" basis, at least for the purposes of this argument . >> >> >> So velocity, momentum etc do not have a real basis, according to your >> >> logic >> >> > I didn't say that. >> >> You said that for anything to be real, it must be the same for all >> observerse .. so yes .. you did > > It depends what we mean. All observers agree on, for example, the > velocity between any two objects. No .. they don't >> >> > And indeed, a lot of the things you may be working with and >> >> > measuring >> >> > in physics are "apparent" and not "real". And I will state the >> >> > definition of "apparent": "appearing as such but not necessarily >> >> > so". >> >> >> So velocity, momentum etc do not have a real basis, according to your >> >> logic >> >> > I didn't say that. >> >> You said that for anything to be real, it must be the same for all >> observerse .. so yes .. you did > > Yes, but the opposite of "real" here is not "imaginary", I didn't say it was > it is > "apparent". I want to avoid discussing unrelated topics, especially > when I can tell intuitively that when you use phrases like "do not > have a real basis", That was what YOU said > you have failed to grasp the meaning that I'm > employing, and what is more, you now propose I spend time defining a > word in relation to concepts that it did not need to be defined for. No .. I'm pointing out that your definition of 'real' makes other things (like velocity) NOT real. > As I said, it seemed to me that everyone understood the meaning of the > words "apparent" and "real" when I mentioned the spaceship on the > television monitor. Yes. That does not mean you use of 'real' is valid in all cases. > Why is it so hard to generalise from that, and > accept that appearances do not always reflect reality, They don't. But you are claiming anything that isn't the same for all observers is not real, and just apparent. > and what > appears to be the case may not be the case? That's really all I'm > getting at here, when I say that while length contraction may *appear* > to occur, it is merely that, an appearance. There is no mechanical, > physical, material, concrete contraction at all. A pole physically fits between the doors of the barn at a given time. The length between its atoms are closer together. You seem to be stuck on the assumption that, unlike velocity, length must be the same for all observers. It isn't > And although you insist the length contraction is real, until you > indicate convincingly that you even know how to discern between > appearance and reality, I'm not going believe you when you simply > assert that the contraction is real. Then use 'frame independent' instead of 'real' .. as that is what you mean. And use 'frame depenendent' instead of 'apparent' .. as that is what you mean. If you are going to discuss physics, use the appropriate terms that have well defined meanings. >> >> >> So if you stand on the the highway and a car travelling at 100km/h >> >> >> runs >> >> >> into >> >> >> you, you don't need to worry, because it isn't really travelling >> >> >> fast >> >> >> (velocity isn't real by your standard), and doesn't really have a >> >> >> large >> >> >> amount of momentum and kinetic energy (momentum and kinetic energy >> >> >> isn't >> >> >> real by your standard) that it imparts into you and your death >> >> >> isn't >> >> >> real. >> >> >> > But I will be apparently dead. ;) >> >> >> So you die from apparent causes and not real ones. >> >> > No, I was just joking, as indicated by wink and the follow-on >> > "seriously though"... >> >> But the point remains .. these things that are not 'real', according to >> your >> defintion, really can kill you. > > Looks can kill. :):) > But that's not the point. Sunlight directed through a > magnifying glass can burn, even though people can sit under the sun > fairly harmlessly otherwise. And that is not real? > But the sun only *appears* scorching to > those under the magnifying glass. So it isn't really burning . .my goodness .. are you SERIOUS ??? > That's not to say the resulting > burns are "not real", but there is a question as to whether the sun is > "inherently" scorching, Go to the surface of the sun and find out > or whether it is because you have manipulated > the sun's rays with a lens. Of course it has been. That doesn't mean it isn't real. But there are no optical illusions or lenses involved in the effects of SR > Or perhaps to put it another way, when you > look through the magnifying glass at the sun, does it "really" become > inherently small and intense (and does looking through the lens > "really" cause a contraction in the sun, despite it being millions of > miles away), or are you just manipulating the rays again? But there are no optical illusions or lenses involved in the effects of SR >> >> > Seriously though, I didn't say velocity was "not real", >> >> >> Yes .. you did .. when you said something is only real if it is the >> >> same >> >> for >> >> all observers >> >> > Yes, indeed. And the hammer hits the skull with the same velocity, the >> > same force, and with the same effect, according to all observers. I >> > really don't see what is difficult about this. >> >> But the velocity of the hammer is different in different frames .. and >> so, >> by your definition, is not real > > No, the velocity of the hammer *relative to the skull* is invariant > across all frames. No its not. it is only approximately so for frames that are not moving very fast relative to each other. > Hence, by my definition, it *is* real. No .. it isn't >> > Or, you can >> > think of it as an interaction between two objects that all observers >> > agree about (and which is not relative, like the skull-cracking >> > scenario). >> >> No .. they do NOT all agree about it, because it is, like velocity and >> momentum and energy etc, a frame-dependent interaction > > Then you're back to saying that according to one observer, the hammer > completely shatters the skull and kills the man, whereas according to > another observer, the hammer blow merely dazes the man I never claimed that > - because, > after all, "energy and momentum are frame-dependent", They are > and if there is > a different amount of energy and momentum in the hammer, There is > a therefore > different amount of force applied to the skull, But there is also different momentum and energy in the skull > then by your own > reasoning, the above is a valid argument. Nope .. that is not my reasoning at all > Except, of course, we both > know it's absurd. Well. . if you say things that I don't say, it will be absurd. That is your problem in misunderstanding what I say, not my problem. >> >> > about my "speaking >> >> > clock" - I had previously said that it ticked loudly, but let's make >> >> > it even more easy to imagine by saying that it consists of just >> >> > black >> >> > box with an audio speaker, and it "speaks" the time out loud every >> >> > second. Do you not accept that the faster you move away from the >> >> > speaking clock, the slower the clock appears to go? >> >> >> That's an audio illusion (or optical if you are reading the time) due >> >> to >> >> delays in signal. >> >> >> That is NOT what happens in SR when we say clocks are measured as >> >> running >> >> slow. >> >> > Well, do you accept that this is at least *one* of the causes of why a >> > clock will appear to run slow? >> >> That you can ALSO have optical (and audio) illusion does not mean that >> that >> is the cause of the SR effect being discussed > > Yes, but can we nail this down first. Is this optical/audio effect > relevant to SR? No > Does it explain at least *partly* the observations in > SR? No > I mean, you must concede, the parallels are startling. No .. they are not at all startling, nor is there anything parallel about it ... except that there is a difference in what one observes.
From: PD on 6 Apr 2010 11:28
On Apr 5, 6:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > > On Apr 5, 3:47 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". > > > 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). I'm not sure what the fuss is. The observation is that the doors are shut and open without striking the pole, and this is true in both reference frames examined (as well as any other inertial reference frame). The account in the ladder frame is, however, not because the ladder fits inside the barn. It is exactly as I described above. Why is this difficult? |