A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: mpalenik on 5 Mar 2010 16:15 On Mar 5, 3:55 pm, mpalenik <markpale...(a)gmail.com> wrote: > On Mar 5, 3:47 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > > > > On Mar 5, 3:07 pm, mpalenik <markpale...(a)gmail.com> wrote: > > > > On Mar 5, 2:17 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > > On Mar 5, 1:54 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > [discussing the scenario in which two clocks symmetrically accelerate > > > > toward each other and this is observed from the point of view of one > > > > of the clocks] > > > > > > Your initial assertions are correct. Both will report a slow down.... > > > > > During part of the trip. And a different slowdown during a different > > > > > part of the trip. > > > > > I should correct myself here. > > > > > The part I wrote about "a different slowdown during a different part > > > > of the trip" was an erroneous reference to a scenario in which a clock > > > > is reporting the Doppler shift that is _seen_ (i.e. without accounting > > > > for transit delays). > > > > In fact, what I was trying to describe to Ste was the effects that are > > > specifically not due to Doppler shifting, as I was specifically making > > > the point that the predictions of SR for time dilation are > > > mathematically different than those which are due to the observed rate > > > of change on a ticking clock to transit delays. > > > Ok good. So we're both not talking about that. > > > > > In such a scenario, the clock sees an interval after it has > > > > accelerated and before its peer has accelerated and then a second > > > > interval after the peer has accelerated. The Doppler shifts for the > > > > intervals are, of course, different. > > > > > In the scenario at hand we are trying to discuss what is _observed_ > > > > (i.e. accounting for transit delays and adopting particular standards > > > > of simultaneity) > > > > No, that's not actually what we were talking about at all. > > > > What is _observed_ is only a single interval during which the two > > > > clocks are in constant relative motion, not two such intervals. [From > > > > an "observed" point of view, the period when the peer clock remains > > > > motionless does not fall within the interval of the journey. Instead, > > > > it is in the relative past] > > > > The relevant quantity was the time that each clock displays after the > > > two are brought into comoving frames, which once again, depends on the > > > frame that they are brought into. > > > In the scenario in question they are not brought into co-moving frames > > (whatever that means -- the notion of things being "brought into" > > frames is very questionable) They are brought _TOGETHER_. > > All I can say is read what I originally wrote again. > > BTW, "together" is ambiguous. Together can mean comoving or it can > mean "they pass each other." Each of those warrants a different > answer.- Hide quoted text - > > - Show quoted text - Just to elaborate, what I said was that if one clock or the other accellerates, the situation is no longer symmetric and will affect the time each clock reads respectively. And the notion of comoving frames is not questionable at all. It's standard terminology in the literature.
From: jbriggs444 on 5 Mar 2010 16:19 On Mar 5, 3:55 pm, mpalenik <markpale...(a)gmail.com> wrote: > On Mar 5, 3:47 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > > > > On Mar 5, 3:07 pm, mpalenik <markpale...(a)gmail.com> wrote: > > > > On Mar 5, 2:17 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > > On Mar 5, 1:54 pm, jbriggs444 <jbriggs...(a)gmail.com> wrote: > > > > [discussing the scenario in which two clocks symmetrically accelerate > > > > toward each other and this is observed from the point of view of one > > > > of the clocks] > > > > > > Your initial assertions are correct. Both will report a slow down.... > > > > > During part of the trip. And a different slowdown during a different > > > > > part of the trip. > > > > > I should correct myself here. > > > > > The part I wrote about "a different slowdown during a different part > > > > of the trip" was an erroneous reference to a scenario in which a clock > > > > is reporting the Doppler shift that is _seen_ (i.e. without accounting > > > > for transit delays). > > > > In fact, what I was trying to describe to Ste was the effects that are > > > specifically not due to Doppler shifting, as I was specifically making > > > the point that the predictions of SR for time dilation are > > > mathematically different than those which are due to the observed rate > > > of change on a ticking clock to transit delays. > > > Ok good. So we're both not talking about that. > > > > > In such a scenario, the clock sees an interval after it has > > > > accelerated and before its peer has accelerated and then a second > > > > interval after the peer has accelerated. The Doppler shifts for the > > > > intervals are, of course, different. > > > > > In the scenario at hand we are trying to discuss what is _observed_ > > > > (i.e. accounting for transit delays and adopting particular standards > > > > of simultaneity) > > > > No, that's not actually what we were talking about at all. > > > > What is _observed_ is only a single interval during which the two > > > > clocks are in constant relative motion, not two such intervals. [From > > > > an "observed" point of view, the period when the peer clock remains > > > > motionless does not fall within the interval of the journey. Instead, > > > > it is in the relative past] > > > > The relevant quantity was the time that each clock displays after the > > > two are brought into comoving frames, which once again, depends on the > > > frame that they are brought into. > > > In the scenario in question they are not brought into co-moving frames > > (whatever that means -- the notion of things being "brought into" > > frames is very questionable) They are brought _TOGETHER_. > > All I can say is read what I originally wrote again. > > BTW, "together" is ambiguous. Together can mean comoving or it can > mean "they pass each other." Each of those warrants a different > answer.- Hide quoted text - > > - Show quoted text - No it doesn't, dufus.
From: BURT on 5 Mar 2010 17:31 On Mar 5, 9:46 am, PD <thedraperfam...(a)gmail.com> wrote: > On Mar 5, 10:41 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > > > > > On Mar 5, 1:51 pm, "Inertial" <relativ...(a)rest.com> wrote: > > > > "Y.Porat" <y.y.po...(a)gmail.com> wrote in message > > > >news:868926cb-233d-417e-86c8-cd8987c43419(a)q16g2000yqq.googlegroups.com.... > > > > > On Mar 4, 7:44 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > >> On Mar 4, 11:09 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > >> > On 4 Mar, 16:48, mpalenik <markpale...(a)gmail.com> wrote: > > > > >> > > On Mar 4, 10:19 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > >> > > > On 4 Mar, 12:19, "Inertial" <relativ...(a)rest.com> wrote: > > > > >> > > > > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > > >> > > > > > Not really, because if the total acceleration is small, then so > > > >> > > > > > is the > > > >> > > > > > speed. > > > > >> > > > > That is a nonsense argument. Acceleration can be small and > > > >> > > > > speeds very > > > >> > > > > large. > > > > >> > > > When I went to school, you could not have a large change of speed > > > >> > > > with > > > >> > > > only a small amount of total acceleration. > > > > >> > > The problem is your use of the term "total acceleration". If by > > > >> > > total > > > >> > > acceleration, you mean integral(a dt), then yes, you are correct. > > > >> > > However, there is already a word for integral(a dt) -- it's called > > > >> > > "the change in velocity". The term "total acceleration" isn't > > > >> > > actually defined. Acceleration is defined, velocity is defined, > > > >> > > deltav is defined. But "total acceleration is not". > > > > >> > Essentially, I'm defining "total acceleration" as something akin to > > > >> > total force, so that even though the force may be small, if it > > > >> > continues for a long time then the total force will be the same as if > > > >> > a large force was applied for a short period of time. In this way, if > > > >> > the application of force is what is causing either part or the whole > > > >> > of the time dilation effect, then it is the final speed that counts, > > > >> > not how quickly the object reached that speed. > > > > >> Indeed. This should tell you that it is not the details of the > > > >> acceleration that matter. > > > >> The overly simplistic statement would be, "Yes, you see that is why > > > >> SR's effects are based on speed, not on acceleration." > > > > >> In fact, there is a speed time dilation effect on GPS satellites, > > > >> which are going around in a circular path at constant speed, relative > > > >> to earth clocks, and accounting for this is crucial to their proper > > > >> operation. This is the same speed dilation effect, though different > > > >> size, as seen in muons in a circulating ring. (Since, by the way, the > > > >> GPS satellites are certainly not inside a magnetic ring but still > > > >> experience time dilation properly calculated by SR, this is another > > > >> good way to be sure that the magnetic ring is not what's responsible > > > >> for the time dilation of the muons.) > > > > >> Regarding something I alluded to earlier, though, what really matters > > > >> is how straight the path through spacetime is. We're used to thinking > > > >> that the shortest path through space is the straight one (and that's > > > >> right), but the straightest path through spacetime yields the LONGEST > > > >> duration. Any change in motion (such as an acceleration) introduces a > > > >> kink in this path (something that can be illustrated visually very > > > >> easily) and so lowers the duration. Why this is, has to do with the > > > >> structure of spacetime and we could discuss that. But this is perhaps > > > >> the most intuitive way (once these concepts are explained) to > > > >> understand why the traveling twin returns younger. > > > > >> > > Also, you could just be dealing with a system where the velocity > > > >> > > started out high and you never measured any acceleration. > > > > >> > Indeed. > > > > > ---------------------- > > > > (:-) > > > > to mix **biologic process** with > > > > inorganic physics > > > > is ridiculous!!! > > > > He didn't .. there was no biologic process mentioned in the above. > > > > > (i said it in a big understatement ...(:-) > > > > Y.Porat > > > > ----------------------- > > > here is a quote from PD > > quote > > > 'and so lowers the duration. Why this is, has to do with the > > structure of spacetime and we could discuss that. But this is perhaps > > the most intuitive way (once these concepts are explained) to > > understand why the traveling twin returns younger. > > end of quote > > ------------- > > so the tarveling twin returns younger ???!!! > > Yes. ALL clocks behave this way, including the chemical clocks that > drive biological processes. > > > > > 2 > > if you dont rmind > > EM radiation HAS MASS! > > > therefore it i influenced by gravity > > SIMILAR BUT NOT EXACTLY AS ANY OTHER MASS!! > > no curvature and no shmervature of space > > > but that is again not for born parrots > > BYE > > Y.P > > ------------------------------- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text - Two time rates by gravity and motion can slow down. One rate can be faster than the other. Mitch Raemsch
From: BURT on 5 Mar 2010 21:50 On Mar 5, 6:36 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > Well, let's see who backs you up. > > In SR, time dilation is a real property, and it is observed every day in > particle accelerators and elsewhere. In SR, two twins, blah blah, one will > be older. Do not confuse this with gravitational time dilation under GR; > this is a completely different and independent thing, is orders of magnitude > smaller that SR time dilation for most real world experiments, and was not > predicted until well after the twins paradox was discussed and resolved in > SR. There are two rates or times in the universe; Gravity's strength and changing flow of energy through space. Mitch Raemsch
From: Bruce Richmond on 5 Mar 2010 23:43
On Mar 5, 12:08 am, Jerry <Cephalobus_alie...(a)comcast.net> wrote: > On Mar 4, 10:33 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > > > > > On Mar 4, 10:48 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > Yes, there is. That's what isotropy experiments have determined. I'm > > > surprised you weren't aware of this. > > > Do you mean like this one? > > >http://mysite.verizon.net/cephalobus_alienus/papers/Gagnon_et_al_1988... > > > The author is kind enough to point out problems in some similar > > experiments, while failing to notice any in his own. > > > For example, has he made any assumption about contraction of his > > equipment in the direction of motion? Tom Roberts has written posts > > in this group showing where some of these experiments are in effect > > two way measurements. > > Do you understand the principle of Gagnon's experiment? Do you > understand the inverse relationship between group velocity and > phase velocity that exists in a wave guide? Do you understand > that length contraction would be a second order phenomenon, while > Gagnon's experiment should be sensitive to first order, assuming > an anisotropy exists? Do you understand that Gagnon's experiment > is a true one-clock measurement of OWLS anisotropy? Do you > understand the difference between an attempt to detect OWLS > anisotropy versus an attempt to perform a one way light speed > measurement? I know what OWLS is, and I know what assume means. > On the negative side, I probably know a lot more about defects > in Gagnon's experiment than you have ever dreamed of. Gagnon > drove the wave guides near cutoff. What does that imply about > heating? Take a good look at the test theory that they used to > analyze their results. Do you notice something about its internal > consistency in terms of an important criterion that I shall not > name, but which you ought to be aware of? Is the fact that the > test theory does not meet this standard of internal consistency > important in their analysis? Can you guess what this problem is? > Can you guess why I consider Gagnon et al. to be an important > experiment, despite some problems in analysis? > > Start with the basics. I've given you important clues. How does > Gagnon et al's xperiment work? I haven't looked it over that closely but off hand I would say it is a gussied up MMX. > > Recently I have been going back and re-reading some of the books I > > have bought over the years to see if I can come to grips with some of > > the modern interpertations of SR. After thinking about it for awhile > > I have realized that my objections about the changing definition of c > > were petty/anal. An analogy would be that there used to be 24 hours > > in a day, 60 minutes in an hour, and 60 seconds in a minute. Now we > > have defined a second as so many transitions of an atom, and can > > measure the variation in the length of a day. The new way is better. > > That it is not in perfect agreement with the old doesn't change much. > > There was nothing sacred about the old. So yes, an old dog can be > > taught new tricks :) > > Thank goodness! > > Jerry- Hide quoted text - > > - Show quoted text - |