colp, why did AE use the word "relativity"?
in [Relativity]
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From: Inertial on 21 Jun 2010 19:23 "colp" <colp(a)solder.ath.cx> wrote in message news:c754feb0-5a39-406c-bdc8-4dc9a56ebd53(a)z29g2000vbk.googlegroups.com... > On Jun 22, 12:34 am, stevendaryl3...(a)yahoo.com (Daryl McCullough) > wrote: >> colp says... >> >> >> >> >>1. Light travels at constant velocity, at speed c, in all directions, >> >>independent of the motion of the source. >> >>2. An ideal clock traveling at speed v for time period t will show >> >>an elapsed time of T = t square-root(1-(v/c)^2). >> >>3. An extended object traveling at speed v will, after reaching its >> >>equilibrium shape, be contracted in the direction of motion by a >> >>factor of square-root(1-(v/c)^2). >> >>4. An object not under the influence of any forces will move at >> >>constant speed. >> >>Those are all true in any inertial coordinate system. The final claim, >> >>which is actually derivable from the first 4, (alternatively, >> >>2&3 can be derived from 5) is: >> >>5. If C is an inertial coordinate system, and C' is obtained from C >> >>by a translation, rotation or Lorentz transformation, then C' is >> >>an inertial coordinate system. >> >There is no apparent reason for your selective application of the >> >single clock transform and the time coordinate transform from the >> >second premise, and there is nothing from the premises that would >> >suggest that frame-jumping is prohibited. >> >> I'm not sure what you are asking for, but let me ask: Do you >> believe that you can derive a contradiction from 1-5? If so, >> then show how. > > There is a maxim of law which states: > > Tout ce que la loi ne defend pas est permis. > Everything is permitted, which is not forbidden by law. > > What this means in this context is that it is proper to make > observations from any frame of reference and to make inferences based > upon them, since there is no law, either natural or otherwise which > forbids this. > > Since SR is a theory about natural physical laws, it follows that > there is nothing which forbids those observations and inferences from > taking place within SR, unless the premises of SR prohibit it, either > explictly or by implication. > > So, if we start with the second premise that: > > 2. An ideal clock traveling at speed v for time period t will show an > elapsed time of T = t square-root(1-(v/c)^2). Yeup > ... then before we can say anything about what SR predicts that an > ideal clock will show, we have to know what limitations are placed > upon this (apparently universally applicable) premise by implication, > since there are no explicit limitations in the theory. > > The first limitation is implied by the title of special relativity, > meaning that the prediction only applies to inertial frames of > reference. However, if there is no preferred frame of reference, as is > implied by relativity, then an observation made in one inertial frame > should be consistent with a similar observation made in another > inertial frame. Yeup > If observations made in different inertial frames are treated > differently, then there is a contradiction with the principle of > relativity implied by the title; i.e. that there is no preferred frame > of reference. They aren't > At this point I'll ask a question with respect to the second premise: > What elapsed time will be shown by an clock travelling at constant > speed of 0.866c when a stationary local clock shows an elapsed time of > 1 second? > > The answer, it would seem, is "it depends". It doesn't depend > Apparently you can't > actually apply the second premise directly, but rather that you must > first determine if there are any other observations being made, Nope .. I don't know where you got that nonsensical ide from > and > then adjust the prediction so it is compatible with those predictions. Wrong > Thus rather than looking at the situation from the local frame of > reference, you must adjust your prediction based on another frame of > reference, which I will call the preferred frame of reference. Nope .. that is NOT done > The bottom line is that either the symmetric twin paradox is a real > paradox, or that a preferred frame of reference exists. The bottom line is that you do not understand SR
From: Inertial on 21 Jun 2010 19:24 "colp" <colp(a)solder.ath.cx> wrote in message news:db80f2a2-1ef8-468b-bb43-e2662e3180e3(a)19g2000vbi.googlegroups.com... [snip[ > Re: How old is one twin when the other twin's clock shows 200 seconds? > > You say that I have to answer questions about simultaneity, but isn't > it clear that the twin's clocks are simultaneous as the start of the > experiment? Not at the turn-around .. you know .. the part you keep saying doesn't matter > You say that to know whether two events are simultaneous, you have to > pick > a coordinate system, but if two events occur at the same time and the > same place, then are they not simultaneous regardless of the > coordinate system? The turnaround for each twin is NOT at the same time and place
From: Daryl McCullough on 21 Jun 2010 19:48 colp says... >On Jun 22, 12:34=A0am, stevendaryl3...(a)yahoo.com (Daryl McCullough) >wrote: >There is a maxim of law which states: > >Tout ce que la loi ne defend pas est permis. >Everything is permitted, which is not forbidden by law. > >What this means in this context is that it is proper to make >observations from any frame of reference and to make inferences based >upon them, since there is no law, either natural or otherwise which >forbids this. > >Since SR is a theory about natural physical laws, it follows that >there is nothing which forbids those observations and inferences from >taking place within SR, unless the premises of SR prohibit it, either >explictly or by implication. The point is that a physical theory specifies particular inferences that can be drawn. If you want to draw inferences that go beyond these, then you can certainly do so, but then you aren't exploring that theory, you're making up your own theory. If you discover something new, that's to your credit. If you derive a contradiction, that's your fault. If you apply the Lorentz transformations to a noninertial coordinate system, then it's not SR's fault if you get nonsense. >So, if we start with the second premise that: > >2. An ideal clock traveling at speed v for time period t will show an >elapsed time of T = t square-root(1-(v/c)^2). > >... then before we can say anything about what SR predicts that an >ideal clock will show, we have to know what limitations are placed >upon this (apparently universally applicable) premise by implication, >since there are no explicit limitations in the theory. The limitation, as I said, is that v and t must be measured in an inertial coordinate system. There is also practical limitations in the sense that if a clock smashes into a wall at near lightspeed, it will break, and will no longer act as an ideal clock. >The first limitation is implied by the title of special relativity, >meaning that the prediction only applies to inertial frames of >reference. v and t must be measured in an inertial frame of reference. But relativity doesn't have any problem computing elapsed times on clocks moving noninertially; you just can't base an inertial coordinate system on such clocks. >However, if there is no preferred frame of reference, as is >implied by relativity, then an observation made in one inertial frame >should be consistent with a similar observation made in another >inertial frame. Yes, you can prove that proper time is an invariant: every inertial coordinate system predicts exactly the same elapsed time on a clock traveling from point A to point B. >At this point I'll ask a question with respect to the second premise: >What elapsed time will be shown by an clock traveling at constant >speed of 0.866c when a stationary local clock shows an elapsed time of >1 second? To compute the elapsed time on a clock, you have to specify the end points: elapsed time from what event to what other event? You need to specify the end points in order to compute elapsed time. The endpoints are points *along* the spacetime path of the clock in question. It doesn't do any good to refer to another clock (the stationary clock), unless you say something along the lines of: Let E1 be the event at which the stationary clock shows time t=0. Let E2 be the event at which the stationary clock shows time t=1 second. Let E3 be the event that takes place at the moving clock which is simultaneous with E1 in the frame of the stationary clock. Let E4 be the event that takes place at the moving clock which is simultaneous with E2 in the frame of the stationary clock. This specifies two events along the path of the moving clock: E3 and E4. Now you can ask what is the elapsed time on the moving clock between events E3 and E4. All inertial coordinate systems will agree with this number, although not all coordinate systems will agree that E1 is simultaneous with E3, or that E2 is simultaneous with E4. >The answer, it would seem, is "it depends". If you've unambiguously determine which endpoints you are talking about, every inertial coordinate system will agree about the elapsed time between those endpoints. >Apparently you can't actually apply the second premise directly, >but rather that you must first determine if there are any other >observations being made, and then adjust the prediction so it is >compatible with those predictions. I have no idea what you mean by that. -- Daryl McCullough Ithaca, NY
From: Daryl McCullough on 21 Jun 2010 20:38 colp says... >Re: How old is one twin when the other twin's clock shows 200 seconds? > >You say that I have to answer questions about simultaneity, but isn't >it clear that the twin's clocks are simultaneous as the start of the >experiment? The question "How old is one twin when the other twin's clock shows 200 seconds" means the same thing as "What event at the location of one twin is simultaneous with the event of the other twin's clock showing 200 seconds?" There is no way to answer such a question without specifying a coordinate system. >You say that to know whether two events are simultaneous, you have to >pick a coordinate system, but if two events occur at the same time and the >same place, then are they not simultaneous regardless of the >coordinate system? Right, if two events are at the same place *and* the same time, then everyone will agree they are simultaneous. -- Daryl McCullough Ithaca, NY
From: Inertial on 21 Jun 2010 21:06
"Daryl McCullough" <stevendaryl3016(a)yahoo.com> wrote in message news:hvp0m001gnk(a)drn.newsguy.com... > colp says... > >>Re: How old is one twin when the other twin's clock shows 200 seconds? >> >>You say that I have to answer questions about simultaneity, but isn't >>it clear that the twin's clocks are simultaneous as the start of the >>experiment? > > The question "How old is one twin when the other twin's clock shows > 200 seconds" means the same thing as "What event at the location > of one twin is simultaneous with the event of the other twin's > clock showing 200 seconds?" There is no way to answer such a > question without specifying a coordinate system. > > >>You say that to know whether two events are simultaneous, you have to >>pick a coordinate system, but if two events occur at the same time and the >>same place, then are they not simultaneous regardless of the >>coordinate system? > > Right, if two events are at the same place *and* the same time, > then everyone will agree they are simultaneous. And events at the identical time and place are the ONLY events that ALL inertial observers will agree are simultaneous (trivailly). IE .. any pair of events NOT at the same location in space CANNOT be agreed on as being simultaneous by ALL inertial observers. Further, there are pairs of events that ALL inertial observers will agree are NOT simultaneous. |