Known physics defeated by simple puzzle?
in [Relativity]
|
From: Inertial on 4 Apr 2010 18:35 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:d1cb0563-6665-4270-bee8-f0bd10b5c9fc(a)q16g2000yqq.googlegroups.com... > On 4 Apr, 15:14, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:265c67a2-6691-4173-be60-e9e93373bf3d(a)30g2000yqi.googlegroups.com... >> >> >> >> >> >> > On 4 Apr, 14:15, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >>news:9b9f09c2-c45f-4169-9aa6-ba7a107de57f(a)k19g2000yqn.googlegroups.com... >> >> >> > On 4 Apr, 12:38, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >> > I give three people a photographic >> >> >> > filter each, all different colours, and they hold it front of >> >> >> > their >> >> >> > eyes. I ask them to look at the sky, and they each comment that >> >> >> > the >> >> >> > sky has changed colour. I now ask them "has the sky really >> >> >> > changed >> >> >> > colour?". Now how would you interpret my question, and how would >> >> >> > you >> >> >> > answer that question? >> >> >> >> The light reaching them has different colors, because certain >> >> >> frequencies >> >> >> are filtered out. >> >> >> > So when I ask "has the *sky* changed colour?" you will say "no"? >> >> >> Just sticking my 2 cents worth in here. >> >> >> I'm not sure I understand what you mean by the term "the colour of the >> >> sky" >> >> in this context. You seem to want it to mean two different things. >> >> >> If you define it to mean the colour seen by an observer looking >> >> through >> >> filters, then the colour does change. >> >> >> If you define it to mean the colour seen by an observer not looking >> >> through >> >> filters, then the colour doesn't change. >> >> >> So when you say "the colour of the sky", how are you defining this >> >> term >> >> in >> >> the context of this experiment? >> >> > The question of what I mean by the "colour of the sky" is not actually >> > that important - it can be given its everyday meaning. The real >> > question is about the cause of the change, and *what* is changed. >> > Placing a filter in front of one's eyes clearly doesn't cause any >> > measurable change in the colour of the sky (if it did, everybody would >> > be able to see the sky turn red when just one person in the whole >> > world put a red filter over their eyes). >> >> > And of course, the real question behind this is about "length >> > contraction". I'm trying to get an idea of whether length contraction >> > is real (i.e. the sky has turned red for everyone - the whole universe >> > has contracted), or whether the relativistic speeds cause a sort of >> > lensing effect (i.e. like putting a prism in front of one's eyes, the >> > "contraction" affects only the person with the prism in front of their >> > eyes) that makes everything *appear* contracted, but there is actually >> > no measurable change at all in the rest of the universe. >> >> You seem to think that something can only be real if it is the same for >> everyone .. so the pitch of a train whistle is not 'real', the velocity >> that >> an object travels at is not 'real' etc etc. By your definition, very >> little >> that we measure in physics is 'real'. >> >> I think your problem here is what you mean by 'real'. > > I'll avoid making a wisecrack here, Wise > but I've explained what I mean by > real, I know you have .. and as I showed above, it is a silly definition > and everyone seemed to agree that the spaceship on the monitor > was not "really" in the sky. Of course it isn't. That doesn't make your definition any better. > That is the essence of what I mean by > "real" (and, conversely, what I mean by "apparent"). Then almost everything you measure an observe is not real. Velocity, momentum ,energy, clock rates, lengths, positions .. all not real.
From: Inertial on 4 Apr 2010 18:36 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:8185f44e-a0bb-4c3d-906e-117c1616aaf6(a)q15g2000yqj.googlegroups.com... > On Apr 4, 10:28 am, "Peter Webb" >> > or whether the relativistic speeds cause a sort of >> > lensing effect (i.e. like putting a prism in front of one's eyes, the >> > "contraction" affects only the person with the prism in front of their >> > eyes) that makes everything *appear* contracted, but there is actually >> > no measurable change at all in the rest of the universe. > > ================== > >> >> No, its not an optical illusion, for the 8 billionth time. >> >> The travelling twin really is younger. >> >> The ladder really does fit inside the barn. > > In spite of recent cautions not to appeal to authority, > I think you will find some important contributors > to Einstein's relativity are diametrically opposed > to you view. > > << Application of Noether's theorem allows physicists to > gain powerful insights into any general theory in physics, > by just analyzing the various transformations that would > make the form of the laws involved invariant. For example: > > * the invariance of physical systems with respect > to spatial translation (in other words, that the laws > of physics do not vary with locations in space) gives > the law of conservation of linear momentum; > * invariance with respect to rotation gives the law > of conservation of angular momentum; > * invariance with respect to time translation gives > the well-known law of conservation of energy >> > http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications > > Nina Byers (1998) > "E. Noether's Discovery of the Deep > Connection Between Symmetries and Conservation Laws." > http://arxiv.org/abs/physics/9807044 As usual, Sue's posts are irrelevant quotes and link mining.
From: Inertial on 4 Apr 2010 18:41 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:61e00417-8601-4438-893a-b92d5aac2242(a)r18g2000yqd.googlegroups.com... > On 4 Apr, 15:28, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:265c67a2-6691-4173-be60-e9e93373bf3d(a)30g2000yqi.googlegroups.com... >> >> >> >> >> >> > On 4 Apr, 14:15, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >>news:9b9f09c2-c45f-4169-9aa6-ba7a107de57f(a)k19g2000yqn.googlegroups.com... >> >> >> > On 4 Apr, 12:38, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >> > I give three people a photographic >> >> >> > filter each, all different colours, and they hold it front of >> >> >> > their >> >> >> > eyes. I ask them to look at the sky, and they each comment that >> >> >> > the >> >> >> > sky has changed colour. I now ask them "has the sky really >> >> >> > changed >> >> >> > colour?". Now how would you interpret my question, and how would >> >> >> > you >> >> >> > answer that question? >> >> >> >> The light reaching them has different colors, because certain >> >> >> frequencies >> >> >> are filtered out. >> >> >> > So when I ask "has the *sky* changed colour?" you will say "no"? >> >> >> Just sticking my 2 cents worth in here. >> >> >> I'm not sure I understand what you mean by the term "the colour of the >> >> sky" >> >> in this context. You seem to want it to mean two different things. >> >> >> If you define it to mean the colour seen by an observer looking >> >> through >> >> filters, then the colour does change. >> >> >> If you define it to mean the colour seen by an observer not looking >> >> through >> >> filters, then the colour doesn't change. >> >> >> So when you say "the colour of the sky", how are you defining this >> >> term >> >> in >> >> the context of this experiment? >> >> > The question of what I mean by the "colour of the sky" is not actually >> > that important - it can be given its everyday meaning. The real >> > question is about the cause of the change, and *what* is changed. >> > Placing a filter in front of one's eyes clearly doesn't cause any >> > measurable change in the colour of the sky >> >> If by "measurable change in the colour of the sky", you mean the colour >> measureed by people not wearing glasses, then yes. > > No, what I mean is that there is some inherent attribute to the sky > (it's "colour"), and that attribute is not changed by the placing of a > filter between the eye and the sky. In other words, nothing happens to > the sky (as a concrete object in the external world) when you put a > filter in front of your eyes. > > > >> > (if it did, everybody would >> > be able to see the sky turn red when just one person in the whole >> > world put a red filter over their eyes). >> >> > And of course, the real question behind this is about "length >> > contraction". I'm trying to get an idea of whether length contraction >> > is real (i.e. the sky has turned red for everyone - the whole universe >> > has contracted), >> >> No, "real" is not the same as "is observed the same by everyone" > > I didn't say it was. The essence of "real" is about describing the > fundamental attributes of some object (in this case, "the colour of > the sky"). My intention is not to argue all day about what I mean by > "the sky" or "the colour". I think there is already a sufficient > common understanding between us in respect of what I mean when I refer > to "the sky" and "its colour", and if you are a materialist as you > claim to be then this shouldn't be a problem. > > > >> If you choose to interpret as "real" only those things which are observed >> the same by everyone, then "lengths" are not "real". And nor are sound >> frequencies; as they depend on the speed of the observer. And nor for >> that >> matter is the colour of the sky real, because different observers see it >> differently (depending on whether they are looking through filters). > > No, what is "real" has *nothing to do* with observation. That's the > essence of materialism versus idealism, as regards this question. > Materialists hold that there is an external world, that has a concrete > existence with form, properties, and attributes, that are totally > independent of observation and independent of any observer. That is > why we say the spaceship on the monitor is not "real", because we know > that the "sky" (as an object depicted on the monitor) does not > *really* contain a spaceship. And yet, it *appears* that there is a > spaceship in the sky, so we say it is *apparent*. > > > >> > or whether the relativistic speeds cause a sort of >> > lensing effect (i.e. like putting a prism in front of one's eyes, the >> > "contraction" affects only the person with the prism in front of their >> > eyes) that makes everything *appear* contracted, but there is actually >> > no measurable change at all in the rest of the universe. >> >> No, its not an optical illusion, for the 8 billionth time. >> >> The travelling twin really is younger. > > We agreed last time that if the two twins both go into space, in > opposite directions, and then return, then they remain the same age as > each other (technically, they both end up younger by the same amount, > than a person who stayed on Earth). Irrelevant to the 'twins paradox'. > This is due to acceleration, Well. to change in rest inertial frame > 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 >> The ladder really does fit inside the barn. > > But then it must fit inside the barn from *all* frames, Why? 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? > 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). 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.
From: Ste on 4 Apr 2010 19:42 On 4 Apr, 23:41, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > or whether the relativistic speeds cause a sort of > >> > lensing effect (i.e. like putting a prism in front of one's eyes, the > >> > "contraction" affects only the person with the prism in front of their > >> > eyes) that makes everything *appear* contracted, but there is actually > >> > no measurable change at all in the rest of the universe. > > >> No, its not an optical illusion, for the 8 billionth time. > > >> The travelling twin really is younger. > > > We agreed last time that if the two twins both go into space, in > > opposite directions, and then return, then they remain the same age as > > each other (technically, they both end up younger by the same amount, > > than a person who stayed on Earth). > > Irrelevant to the 'twins paradox'. It isn't, because what I'm showing is that the time dilation in SR is due to acceleration, which is not relative. 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=false > > This is due to acceleration, > > Well. to change in rest inertial frame Never mind, for now. > > 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, whereas SR treats acceleration merely as a change of relative velocity (which may or may not involve "real" acceleration - the kind that would be registered on an accelerometer). > >> 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. > 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. If I hit someone over the head with a hammer, then the force applied to the skull depends on the relative speed of the hammer and the skull. But all observers agree about the force of the impact between the hammer and the skull - in other words, I do not crack his skull wide open according to some observers, and merely daze him according to others. 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. 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". > > 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 . 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 when we talk of "clocks slowing down", we need to be clear about whether we're talking about the clock *appearing* to slow down (but continuing to tick at the normal rate), or whether it is *really* slowed down. (More on this below.) > 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. ;) Seriously though, I didn't say velocity was "not real", but it is a relative concept (that is, it is an interaction of two objects, not a property of one object; and it is still invariant across all frames, in that the car hits the person with the same force, and the same effect, no matter where you look at it from). Also, I'd be interested to return to a discussion 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?
From: Peter Webb on 4 Apr 2010 20:26
"Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:8185f44e-a0bb-4c3d-906e-117c1616aaf6(a)q15g2000yqj.googlegroups.com... On Apr 4, 10:28 am, "Peter Webb" > > or whether the relativistic speeds cause a sort of > > lensing effect (i.e. like putting a prism in front of one's eyes, the > > "contraction" affects only the person with the prism in front of their > > eyes) that makes everything *appear* contracted, but there is actually > > no measurable change at all in the rest of the universe. ================== > > No, its not an optical illusion, for the 8 billionth time. > > The travelling twin really is younger. > > The ladder really does fit inside the barn. In spite of recent cautions not to appeal to authority, I think you will find some important contributors to Einstein's relativity are diametrically opposed to you view. ________________________________________ OK, name one physicist who believes that the travelling twin would not return younger. |