Certainly not some kind of magical force that messes only with clocks.

The clock on your desk can't be used as an example of relativity (by you at least) because it's not moving at relative speed to you. It would have to zoom by you at a goodly portion of the speed of light for you to measure such effects.
Relativity, while having the capacity to change the observed time on a clock to that of your own, isn't affecting only the clock. Every measurable aspect is changed, which means that if everything in the other frame changes, no change is observed within the other frame.
You may recall I said to you Sam5 that relativity only happens to other people.

Yeah there is. Analogies only get you so far, and some (like above) are far less useful than others.

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Again, I think that your problem with relativity is that you think it claims something that it does not, in fact, ever claim. You seem to believe that an observer sitting next to a clock will suddenly see the rate of that clock change as a result of the observer and the clock moving relative to some other observer, and you're convinced that the rate of a the clock can't change because there's no physical force on it.

However, relativity theory never suggests that this happens, and it's a mistake to think it does. If you have a clock with you, you can move however you want, and other people can move relative to you however they want, but as long as you and the clock stay together, you'll see it ticking merrily away at the rate you'd expect.* What relativity does predict is that other people may see your clock tick at a different rate, depending on how they are moving relative to you.

Now, since one of the postulates of relativity is that the two reference frames are equally valid, either description should be considered acceptable, and we have a nice set of equations that allows me to figure out what you'll see if I know what I see, or vice versa.

But it does! How else can I tell what rate a clock is ticking at unless I look at it? The light signals are just a conveniently amplified way that I can look at a distant clock, nothing more. It's true that some of the shift in apparent rate is from a Doppler. However, from experiment, if I try to use the classical Doppler formula to work out what I should see, I get the wrong answer. It turns out that there are other effects as well when the relative velocity of the reference frames is close to the velocity of light,and relativity shows that I can derive these additional effects from a couple simple postulates.


* Depending on the type of clock, it's rate may change if the force of gravity is different, or if the temperature or other external parameters are changed. But in each case, you could in principle work out what effect the external change should have, and your clock will always appear to you to be ticking at exactly the rate you would predict.

I just wanted to say these are all true, and to note that while real effects, a definition of relativity they do not make. I know that you know this, Grey, but I'm sure someone does not.

Absolutely! I specifically chose to put that in a footnote to make it clear that these effects have nothing to do with relativity and everything to do with the mechanics of the clock, but you are probably correct that it's worth stating that explicitly.

Not really. Hafele and Keating claimed to measure an atomic clock shift during a 600 mph airplane ride.

The steady straight-line motion of a clock in deep space is not affecting the clock at all. Light signals bouncing off of or originating at the moving clock produces an illusion that is seen by the observer.

That's because nothing changes in the other frame because nothing happens in the other frame if the motion is straight-line and unaccelerated. These are optical illusions seen at the observer.


You observe things seem to happen to other people, but with simple visual illusions, they don't actually happen to the other people. It's like when you watch a slo-mo scene of a football game on tv. The players aren't really moving in "slow motion".


What you are talking about mainly is the common Doppler effect. Not only is a 1 second 1,000 Hz blast on a moving-train whistle observed to be of a lower frequency when received by a stationary observer standing on the track at the rear of the train, but the observer hears the redshifted blast last for more than one second at the observer. This gives the illusion that “time dilation” has taken place at the train whistle, but it actually has not.

If you use a gun and fire one shot per second on the rear platform of a moving train, a rear stationary observer on the ground will hear the shots more than one second apart. This is the common Doppler effect. Doppler discovered this in the 1840s.

There are some effects on atomic clocks when they move rapidly through fields and when they accelerate, that cause their oscillation rates to decrease, but these effects are not described by SR theory. Lorentz described them in his book in 1895. That's why he invented the "relativistic Doppler effect". It is caused by a combination of the regular Doppler effect and a slowdown in the physical oscillation rate of atoms.

No, that’s not what I think at all.

But an observer traveling WITH his own clock, who sees his own clock ticking normally and he sees a separate relatively moving clock with a “slow” tick rate, will not find his own clock “lagging behind” the other clock when the two unite. This is impossible, and this is the “clock paradox” of the SR theory. If he does see the other clock with a “slow” tick rate, and if it really does have a slow tick rate, then he will see the other clock lag behind his own when they unite. But the SR theory has two observers seeing each other’s clock “time dilate” in exactly the same amount, but only one of the clocks “lags behind” the other when they unite. That is the paradox, and that is one of the errors of SR theory.

GR theory has no such paradox. In GR the slow clock sees the fast clock tick fast and the fast clock sees the slow clock tick slow. No paradox.

What actually happens, if none of the clocks actually change rates, is that both observers will see each other’s clocks seem to “slow down” while they are moving apart, and seem to “speed up” when they are moving toward each other. These are Doppler effects.

Doppler explained this illusion in 1842. Have you never heard of it before? Do you not read any 19th Century books at all?

Please tell us what “experiments” you have personally conducted where you used the Doppler equations and you got the wrong answer.

Touche. You can apparently measure such effects even at these relatively low speeds. My caveat should have been it needs to be going quite quick to readily observe such effects.

Yes but also the dilation of space-time causes the observed changes in addition to simple doppler shift.

No. There is doppler effects, but they do not encompass what the clocks thought experiment demonstrate. Doppler shift isn't responsible for why the time is different on each clock when they are reconciled. This is true for SR and GR.
If SR produced a paradox and GR did not, then the answers at the end of the thought experiment using each theory would be different. They are not. How can that be when one is apparently wrong?

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It's inaccurate to claim that a simple doppler shift is the entirety of the observations. To do so would be tantamount to denying relativity itself (in any form). I know you support GR, so how can you have this viewpoint?

Everybody already knew this in the 19th Century! Equations regarding it were even published in the 18th Century. Pendulum clocks moved from England and France to near the equator in South America had to be adjusted for gravity effects in the 17th Century.

Here are some of Airy’s early equations on clock drift, from 1826:

1826 EQUATIONS, CLOCK DRIFT DUE TO GRAVITY

AIRY’S GRAVITY-BASED CLOCK DRIFT EQUATION, 1826:




The first relativistic atomic clock drift equations were published by Lorentz in 1895:

LORENTZ, ATOMIC CLOCK DRIFT, 1895

Damn straight everybody knew Sam5... Just remember that this stuff itsn't part time dilation due to relative motion. Relativity isn't the theory of physical effects that can alter the "tick-rates" of different clocks.

I think it would have been much easier for you to have written

T=2*pi*sqrt(L/g)

I'm not sure since I haven't bothered to read that whole link, but I don't think that that integral equation is really necessary to illustrate much of anything. Nor do think that the Lorentz page you posted means a whole lot either. Not in this context anyway. (I'm sure it's still pretty important. :wink: )

Explain the “dilation of space-time” in your own words, please. (No coaching from anyone else, por favor.)


Simple, very simple. In SR, both of two observers “see” each other’s clock slow down, “time dilate”, WHILE the motion takes place, but in Section 4, only one of the two clocks actually “lags behind” the other when they are united. So, both observers DISAGREE about what really happened. The K observer says, “Hey, your clock slowed down.” But the K’ observer says, “No, it was your clock that slowed down.”

Why does this disagreement not show up in Section 4? Because Einstein gave the opinion of ONLY the K observer when the clocks united. He did not give the opinion of the K’ observer.

In GR theory, the guy with the slow clock sees the fast clock tick fast, and the guy with the fast clock sees the slow clock tick slow. No disagreement and no paradox.

To say in SR theory that the clock that “lags behind” is the clock that you did NOT travel with, is absurd. This is a “parallel universe” theory, not a “relativity” theory.

Einstein imagined himself staying fixed with the K clock, so he “saw” the K’ clock “slow down” and he claimed the K’ clock “lagged behind” the K clock when they united. But, I stayed fixed with the K’ clock, and that’s when I saw the paradox.

This means if Einstein had traveled with the K’ clock, then it would NOT have “lagged behind” the K clock at the end, and the K clock would have “lagged behind” the K’ clock. This is silly, stupid, wrong, a mistake, and that’s why there are hundreds of “clock paradox” websites and book pages today. Hundreds of people trying to explain the paradox away, and all using a completely different technique. And this is why Einstein had to add atomic clocks, acceleration effects, and gravity fields, to try to distract from this error when he tried to resolve the paradox in 1918

Yeah, upon closer inspection of the Lorentz text and equations, he's just defining some variables, the first of which looks like an extension of the Laplacian operator, though I'm not 100% sure on the notation. Doesn't seem to useful for clocks, at least not that page.

Have you actually read “On the Electrodynamics of Moving Bodies”? He says in section 4 that not only do the two observers see the same thing in each other’s clock tick rate while the clocks are moving relatively, but he says when the clocks are united, one “lags behind” the other. This takes the theory out of the realm of “optical illusions” and puts it into the realm of “science fiction”.

Sam, as we've said many times before, the theory is all contained in the math. You have to get past that before you can critique it in any credible way. Were you to send a paper into any scientific journal reporting to "disprove" SR, you would need some serious mathematical jargon in it to get anywhere.

Freddo,

There would be no SR clock paradox problem if he had said in the 1905 paper, “Of course, these are optical illusions”, and “when the clocks unite, both show the same reading because neither actually did ‘time dilate’ during the relative motion.”

But he said the “relative motion” actually did cause one of the two clocks to change rates and “lag behind” the other, after he had already said that both observers would “see” each other’s clock time dilate in exactly the same amount during the motion. Well, you can’t slow down two clocks exactly the same amount and then unite them with only one of them “lagging behind” the other when they unite.

Do you not see the problem?