Known physics defeated by simple puzzle?
in [Relativity]
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From: PD on 9 Apr 2010 10:54 On Apr 8, 9:07 pm, Ste <ste_ro...(a)hotmail.com> wrote: > 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. And again, the main thing to remember is that the ladder is moving relative to the barn. > As I say, I don't think we need to discuss extensively > what "fitting" means - but for completeness, it simply means whether > the full extent of the ladder could be at once contained within the > confines of the barn. I completely disagree. This is where the precision of the definition is important. It is only by waving hands generally and dismissively about what a word *means* that you afford yourself enough vagueness to suppose that "fitting" should be a frame-independent concept. As soon as you try to be precise about what "fitting" means, you learn that any precise definition quickly leads to incompatibility with frame- independence. So the conclusion is that if the only way you can secure the frame-independence of the concept is by being vague and loose with what the concept actually means, then you've only succeeded in fooling yourself with an inherently inconsistent concept. > > > 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, so the only other > explanation is that perhaps it *appears* to do this, but does not > actually do so. And again, what we would have to do is to clearly define what simultaneity *means*, so that we can determine whether in fact the frame-dependence of the timing of the doors is real. We've already determined that the *reality* of "fitting* hinges precisely on this statement of simultaneity, and so the question simply shifts to the *reality* of simultaneity. > 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). The "explained somehow" is the part that gets into vigorous hand- waving. It is an appeal to "Surely there is something -- *anything* -- that could account for this other than having to appeal to relativity." That's all well and good, but in the absence of a concrete alternative, there is the fact that relativity does do a proper job of explaining it, whether you find it distasteful or not. When there is something put forward that competes as well as relativity, then surely it will be deserving of consideration.
From: PD on 9 Apr 2010 10:57 On Apr 8, 9:09 pm, Ste <ste_ro...(a)hotmail.com> wrote: > 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. But that is not what happens. For example, if I see a car traveling west at 10 kmh, and a car traveling east at 35 kmh, then you have the expectation that, to a passenger riding in the car traveling east, the other car is traveling 45 kmh west. But in fact, it is not traveling at 45 kmh west to a passenger in that car. It is traveling at something close to that, but only approximately. The bottom line is, the basic sum rule you've been taught for relative velocities is a LIE. PD
From: PD on 9 Apr 2010 11:01 On Apr 8, 9:12 pm, Ste <ste_ro...(a)hotmail.com> wrote: > 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. But there ARE ways of confirming the moon's presence, even when you're not observing the moon. For example, you could predict what would happen to the orbits of other celestial bodies if the moon disappeared when you were not looking at it. Then when you did look again and saw that the moon had at least reappeared, you could test the hypothesis that it had disappeared in between. > > > 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. There are those that believe that angels are real and therefore natural creatures, under the presumption that anything that is real in the universe is also natural. So you'd have to be a little clearer about that which belongs to "naturalistic ideology" and that which does not. PD
From: Sue... on 9 Apr 2010 15:32 On Apr 9, 10:57 am, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 8, 9:09 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > 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. > > But that is not what happens. > For example, if I see a car traveling west at 10 kmh, and a car > traveling east at 35 kmh, then you have the expectation that, to a > passenger riding in the car traveling east, the other car is traveling > 45 kmh west. > But in fact, it is not traveling at 45 kmh west to a passenger in that > car. > It is traveling at something close to that, but only approximately. ========================== > > The bottom line is, the basic sum rule you've been taught for relative > velocities is a LIE. << The main types of particle combinations used at RHIC are p + p, d + Au, Cu + Cu and Au + Au. The projectiles typically travel at a speed of 99.995% of the speed of light in vacuum. For Au + Au collision, the center-of-mass energy \sqrt{s_{NN}} is typically 200 GeV (or 100 GeV per nucleus); >> http://en.wikipedia.org/wiki/Relativistic_Heavy_Ion_Collider > > PD
From: Ste on 9 Apr 2010 15:39
On 9 Apr, 15:24, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > On 8 abr, 21:59, Ste <ste_ro...(a)hotmail.com> wrote: > > > On 8 Apr, 14:53, PD <thedraperfam...(a)gmail.com> wrote: > > > It's not about "faith over evidence". The evidence is meaningless > > without interpretation. The real question, which is the same as it > > ever was in human history, is *how* we are to interpret evidence, not > > *whether* we are to interpret it. > > Let us explore this for a moment, in the form of a very simple > gedanken (I have used this on several occasions). No frame of > references are needed. > > You are aboard a space ship in intergalactic space (meaning you are > very far away from gravitational effects). While in this condition, > you do not feel any force acting on your body (you are weightless > floating inside your space ship). Also, you have aboard a small window > and you are looking through it and, of course you see just a complete > darkness, without galaxies, stars or any other stellar object in your > surroundings. > > Suddenly, you start to see, far away, an object which, with the help > of a telescope, you identify as another space ship (by its use of > flashing red and green beacons). The object appears to be approaching > your location. Now, which of the following assertions is true and > which is false. > > a)Your space ship is not moving and the other space ship is > approaching at a speed v (closing speed measured with a laser gun). > b)Your space ship is moving at a speed v and the other space ship is > not moving. > c)Your space ship is moving at a speed 0.4v towards the other space > ship, which itself is moving at a speed 0.6v towards you. > d)There are infinite solutions of relative speeds satisfying the > observation. > e)All of the previous assertions are true, since speed is a frame > dependent variable. > > So for escape from this multitude of compatible solutions, you have to > choose one of them, which is equivalent to select one of the frames of > reference to calculate the different physical quantities. So for you, > it is easier to select a given point (x0,y0,z0) and given axes (x,y,z) > somewhere inside your ship, as that frame of reference which allows > you to discard all alternatives except (a). I would suggest a sixth solution. That the only "true" and "real" statement that can be made, from the evidence available, is that you and the other spaceship are converging positions at a relative speed of 'v'. |