They’re accelerating.

Then why do they match the SR predictions?

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Particle accelerator is kind of a misnomer. Yes, they have to accelerate at first, but generally when either collisions happen or any other measurements are made, they are travelling with constant velocity (since the EM field is generally constant).

Einstein got many of his SR ideas from the Lorentz electrodynamics relativity theory, and he used the Lorentz transformation equations. See Lorentz’s, “Versuch Einer Theorie Der Elektrischen Und Optischen Erscheinungen In Bewegten Körpern,” Leipzig, 1895. In 1905 he “borrowed” his “constancy” of the speed of light postulate from Lorentz’s theory of the stationary luminiferous ether.

So where is the Aether? Has to be there for the equations to work, after all, Lorentz's equations assume the Aether. You'll also have to expain why Lorentz's equations don't match the observation of uncut magnetic field lines, but SR's do. So go ahead, explain it.

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Some try to tell me, thoughts they cannot defend,... - Moody Blues.

We’ve been over all of this many times before. The title of this thread is “How do theories like relativity hold up with paradoxes?” Some guy asked some questions about paradoxes and I posted my 2¢ worth of opinions. I don’t care to get into a big long “relativity” argument with 6 to 8 guys again.

Even Einstein's 1905 paper treats the effects of acceleration.
Do you not consider relative velocity to be "physical"? If not, what is it, to you?

Apparently non-existent.

Yes, you did. However other opinions differ from yours, those that say there isn't actually any paradox.

Actually, it does.

We have three observers - A, B, and C. A and B are in motion relative to each other. That means that A's motion relative to C is different than B's motion relative to C. SR predicts that A will "see" C differently than B does (and vice versa), and that C will "see" A differently than C "sees" B. There's no acceleration here.

So, if A and B at some point in spacetime pass (neglibly close to) each other, we can simply "switch" from A's measurement of C to B's measurement of C at that moment without dealing with acceleration. We can also "switch" from C's measurement of A to C's measurement of B at that same moment, again without dealing with acceleration.

This is then no different than A simply "becoming" B at that moment, thereby effectively changing its motion relative to C without acceleration.

Thus we can consider an object changing its relative motion without dealing with acceleration.

Now, if we do want to deal with the acceleration, and consider what A/B sees during the switch from A to B, we need GR. But we don't need it to resolve your so-called "paradox."

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SeanF

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The contents of this post are ©2008 by SeanF and may not be copied or retransmitted in any form without the express written consent of SeanF

A common misconception about SR is that it cannot handle acceleration. The reference frames of SR are in uniform unaccelerated motion with respect to one another, but particles in those frames can experience any acceleration as appropriate. SR would be pretty useless if it could not describe accelerating particles!

If you want reference frames that undergo accelerations with respect to one another, then you will have to turn to GR.

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The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

Man, you hit the nail right on the head!

Uh...sam, I coulda swore one of your previous sticking points was that SR didn't deal with acceleration, and thus was flawed. It was this aspect of SR that Einstein tried to cover up in subsequent papers...


Or did I get your position wrong?

No, you just missed the circular agument:

Sam: SR doesn't deal with acceleration, so its wrong.
Everyone: But SR does deal with acceleration.
Sam: See, I told you SR was wrong! :roll:

Hi Sam!

Sam5 wrote:
After milli360 educated me in reference frames (and thanks again, Milli) I resolved not to discuss relativity and reference frames again because I doin't know enough about them. But clocks I do know about, and I feel Sam5's above quote is a bit of a red herring.

The practical problem of using a pendulum clock on a ship is that to ensure accurate timekeeping the pendulum must have an even beat. This requires dead center on the pendulum swing be exactly below the pendulum pivot point (gravity acceleration vector pointing straight down). On a rocking ship the vectors due to gravity and the acceleration due to the rocking will add so that the required condition for accuracy is no longer true. This is trivial and of no more cosmic consequence than levelling the case of a pendulum clock on dry land (of course, the levelling itself is far from trivial in some cases).

H1, Harrison's first attempt, used the dual pivot escapement design as shown in the link Sam5 gives (and it's a good link). The escapement is symmetrical and avoids most of the effects of both minor accelerations and movement position. But note the sheer mass of the design; Harrison was still compensating for other shortcomings by bulking up the escapement.

The real gem is H4, the first real chronometer. It incorporates so many of the new and acccumulated innovations in timekeeping that it must be rated among the most important machines ever built. It uses a weighted, compensated balance wheel with bimetal spring (all for temperature invariance), a low-impulse escapement, going spring for winding, ulralow friction bearings... really the whole nine yards.

Keeping a pendulum clock in beat on a ship really has nothing to do with SR or GR.

For references see Dava Sobel's Longitude, or for a more comprehensive coverage David Landes' Revolution it Time.

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That’s fine.

Back in the early ‘60s we had problems with portable tape recorders. They usually had a single flywheel as a speed stabilizer. But, when they were moved around, the case of the recorder turning either with or against the rotation direction of the flywheel, caused the tape moving across the tape heads to either slow down or speed up. In the late ‘60s, Sony invented a portable tape recorder that had two counter-rotating flywheels, and that alleviated that problem quite a lot.

Even though we are discussing large or "macro" scale effects, the phenomena observed are still “cosmic consequences”. A phenomenon does not have to be microscopic or on the quantum level to be of “cosmic consequences”. Go jump off a cliff and you will realize the “cosmic consequences” of your act.

You are a clock man. I’m something of a clock man too, having worked with all different kinds of clocks in my lifetime. Let’s say you’ve got a clock of any kind sitting on your desk. Now, how do you change the rate of that clock? What do you need to do to get it to change rates?

To RussWaters,

Hi, Russ,

Remember when I told you that Einstein retracted his 1905 “constancy” postulate? Well, he wrote a lot about that in the 1912 to 1915 era, and here is some information from some of the papers from that era, published in a new book I just ordered:

For example, in the 1912 paper, “The Speed of Light and the Statics of the Gravitational Field,” he said:

“But at the same time it turned out that one of the basic principles of that theory, namely, the principle of the constancy of the velocity of light, is valid only for space-time regions of constant gravitational potential. Even though this result rules out the universal applicability of the Lorentz transformation, it should not frighten us away from the further pursuit of the path we have taken...”

And in the 1912 paper, “Relativity and Gravitation”, he says:

“Abraham notes that I have delivered the coup de grace to the relativity theory by abandoning the postulate of the constancy of the velocity of light and by the therewith connected relinquishment of the invariance of the systems of equations with respect to the Lorentz transformations.”

This was in response to statements that Abraham published in the Annalen der Physik:

“Already before a period of one year, A. Einstein, by accepting an influence of the gravitation potential on the speed of light, gave up the postulate of the constant speed of light essential for his earlier theory 1); in a work appeared recently 2)......”

In the 1912 paper, “Theory of Relativity”, as published in “Physik”, Emil Warburg, Leipzig, 1915, he said this about the SR theory:

“Finally, one more important question: Does the theory of relativity possess unlimited validity? Even the supporters of the theory of relativity have different views on this question. The majority are of the opinion that the propositions of the theory of relativity – especially its conception of time and space – can claim unlimited validity.

However, the writer of these lines is of the opinion that the theory of relativity is still in need of a generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned.”

So, the famous “constancy” postulate of the 1905 SR theory did not exist after 1912, and it doesn’t exist today.

Yes, you got it wrong.

SR doesn’t deal with accelerations AND it was flawed.

SR deals with “time dilation” caused by “relative motion” only, and this is an error, since “relative motion” does not slow down or speed up any clocks. The error here is caused by Einstein trying to determine the “tick rate” of a distant clock indirectly, by means of “light signals”. One has to be very careful when one does this, because with “light signals” one does not measure the direct “tick rate” of a distant clock. One measures the “arrival rate” of the “light signals”. Doppler effects often apply, and they produce “timing illusions” at the observer that aren’t really taking place at the distant clock.

Einstein later learned this, starting around 1911, so he began to modify his thought experiments, especially by switching over from using any kind of clock to using specifically an atomic clock.

Then in 1918, when he was fairly familiar with the way atomic clocks were affected by acceleration, then he tried to pretend that “acceleration” was considered in SR theory, and that’s why the K’ clock “time dilated” in that theory.

It was ok for him to recall the “constancy” postulate in 1912, but it was not ok for him to admit that the “time dilation” did NOT take place due only to “relative motion”, because that was what had made him famous, the slow-down of “time itself” due only to “relative motion”. So he could not admit in 1918 that he had been wrong about that, because many of the newspapers would have pointed out his mistake and that would have destroyed his fame.

Relativity states that an object will appear at rest to itself no matter how fast it may be moving wrt the rest of the universe.

Yet if an ion-engined rocket expels exhaust gases at 20,000 miles per second, then the fastest it can go relative to the Earth it left behind is 20,000 mps.

But by Relativity, the rocket reaching 20,000 mps can be viewed as being at rest relative to itself. If we are on the rocket, we should see the gases leaving us at 20,000 mps and we should continue to accelerate.

This is not the case in practice, where the rocket somehow "knows" that it has attained terminal velocity relative to the universe. This can only be the case if the exhaust pushes against both the rocket casing and a medium such as the Aether. This cannot be the cases in an Einsteinian vacuum or in Relativity.

Does that even make sense?

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