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Need help with relativity question: Has "Dingle's Question" ever been answered?

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posted on Sep, 25 2011 @ 06:58 PM
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In another thread about faster than light neutrinos, squiz asked about Dingle's question. Though it involves Einstein's relativity, it was slightly off the topic of the FTL neutrino subject so I thought it might make an interesting thread on its own.

Dingle wrote a book, but there's a pdf which discusses Dingle's question here:

redshift.vif.com...

The author of that pdf claims that Dingle's question has never been answered, and Dingle claimed his question was never answered. Is this true?

I think I can provide a much better answer than Ian McCausland, the author of that pdf from the University of Toronto, let's see if you all agree:


Dingle’s Question

The question that Dingle asked was the central theme of his book
Science at the Crossroads [2], and he claimed that, unless that
question could be answered, the special theory failed. This question
might be worded very briefly as follows: Which of two clocks in
uniform relative motion does the special theory require to work more
slowly?
That is the Ian McCausland's summary of the question, but he also quotes the question in Dingle's own words:


According to the special relativity theory, as
expounded by Einstein in his original paper, two similar,
regularly-running clocks, A and B, in uniform relative
motion, must work at different rates. In mathematical
terms, the intervals, dt and dt’, which they record between
the same two events are related by the Lorentz
transformation, according to which dt ≠ dt’. Hence one
clock must work steadily at a slower rate than the other.
The theory, however, provides no indication of which
clock that is, and the question inevitably arises: How is
the slower-working clock distinguished? The supposition
that the theory merely requires each clock to appear to
work more slowly from the point of view of the other is
ruled out not only by its many applications and by the fact
that the theory would then be useless in practice, but also
by Einstein’s own examples, of which it is sufficient to cite
the one best known and most often claimed to have been
indirectly established by experiment, viz. ‘Thence’ [i.e.
from the theory he had just expounded, which takes no
account of possible effects of acceleration, gravitation, or
any difference at all between the clocks except their state
of uniform motion] ‘we conclude that a balance-clock at
the equator must go more slowly, by a very small amount,
than a precisely similar clock situated at one of the poles
under otherwise identical conditions.’ Applied to this
example, the question is: what entitled Einstein to
conclude from his theory that the equatorial, and not the
polar, clock worked more slowly?
So that is the question.

What is the answer?

The author of that article claims it's never been satisfactorily answered, because the question is about special relativity, and physicists use general relativity to answer the question which they shouldn't do because it's a question about special relativity, not general relativity.

Just a refresher on one of the relevant differences between special and general relativity from a layman's point of view, for those of you not familiar with it:
-Special relativity discusses what happens in uniform (straight line) motion, and it doesn't cover accelerations.
-General relativity does includes the effect of accelerations, such as gravitational, and other forms of acceleration.

Understanding this difference is key to understanding Dingle's question, and the problem with it.

I'll give you my answer to the question but I welcome answers of others if you have a different one.

The question is not a valid question to begin with as Dingle stated it, so it can't have a valid answer.

He claims the question is about special relativity and should be answered with special relativity. However, the example he uses, from Einstein, is why a clock at the equator will run more slowly than a clock at the pole. The clock at the equator is not in a uniform state of motion (meaning it's not moving in a straight line). It's being spun around in circles along with the Earth's surface, accelerated by the Earth's gravity. So what makes the question invalid is, you can't answer a question using only special relativity, when the physics in your question don't involve only special relativity. If the physics involve general relativity, you must use general relativity to answer the question. Why Ian McCausland doesn't recognize this escapes me.

This is why Dingle's question can't be answered with just special relativity, when his example of an object accelerating at the equator is not a special relativity example.

So in summary, what Dingle has done is, ask a question which involves non-uniform motion (acceleration in general relativity) and then demanded that the question be answered using only special relativity (which only applies to uniform motion).

Therefore it's no wonder he claims he never got an answer to his question. Of course you can't answer a question using just special relativity if the question isn't really about special relativity.

If you restrict the question to just examples in special relativity, meaning only involving uniform motion (non-accelerating), the question can be answered with special relativity here as discussed in this link:

casa.colorado.edu...


Vermilion thinks Cerulean's clock runs slow. But of course from Cerulean's perspective it is Vermilion who is moving, and Vermilion whose clock runs slow. How can both think the other's clock runs slow? Paradox!

The resolution of the paradox, as usual in special relativity, involves simultaneity, and as usual it helps to draw a spacetime diagram, such as this one from the Centre of the Lightcone page....
That is truly a special relativity example, because there are no accelerations. If you ask a special relativity question, you can get a special relativity answer.

If you ask a general relativity question you must use general relativity to answer it and you can't complain that it must be answered by special relativity like Dingle and apparently Ian McCausland are doing.

So, who do you think is right? Me, who says it's not even a valid question, or Ian McCausland, the author of that pdf, who apparently thinks it's a valid question which has never been answered?


I suggest that scientists need to answer Dingle’s Question. Since the question was explicitly about the special theory of relativity, I suggest that the answer to the question should have the following properties: it should provide a clear criterion to distinguish which of two clocks in relative motion the special theory requires to work more slowly, the applicability of the criterion to the case of the polar and equatorial clocks should be clear, and the answer should not depend in any way on the general theory of relativity. The world has been waiting more than thirty-five years for Herbert Dingle’s perfectly reasonable question to be answered.
Special relativity doesn't require either of the two clocks to move more slowly, if you just stick to true special relativity examples where there is no acceleration, right?

Whichever inertial frame of reference you're in, the other clock appears to move more slowly.

Isn't that the answer?

Has Dingle's question been satisfactorily answered? Your thoughts please.
edit on 25-9-2011 by Arbitrageur because: fixed external source quote




posted on Sep, 25 2011 @ 08:39 PM
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reply to post by Arbitrageur
 


CLPrime agrees with you. How does that make you feel?


Though, I do have a problem with people separating Special and General Relativity. SR is merely a special case within the broader scope of GR. The only reason the two appear so different is that GR required more advanced mathematics. Vectors became tensors. Minkowski space becomes Riemannian space. Gravity becomes a stress-energy tensor. It's all in the family.



posted on Sep, 25 2011 @ 08:54 PM
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reply to post by CLPrime
 

It made me feel like starring your post, though even if you disagreed with me and you provided a logical explanation why, I'd still star it.

I had some concerns about the separation of GR and SR too. Part of the dialog in this debate is that there was over a decade after 1905 where the special relativity paper had been published (in 1905) but the general relativity paper hadn't been published yet.

So they want us to think of this question in the context of 1910, when there was no general theory of relativity, and the special relativity theory had to stand on its own merit. While I understand the argument, I also looked at my calendar and noted it's not 1910 anymore. Now that we do have the general theory of relativity, I don't see a problem using it where it's applicable.



posted on Sep, 25 2011 @ 09:03 PM
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reply to post by Arbitrageur
 


Indeed. The reason GR was needed was because SR was incapable of mathematically describing non-uniform motion. If this question had been asked of Einstein when he published his paper on SR, he would've said to wait for the paper on GR, because this is exactly the kind of question GR designed to answer.

Expecting to answer it with SR is like asking what 10! means in the context of a course in English. Nonsensical expectations get nonsensical results.

Also, in Relativity, it's generally idiotic to ask "which one" in the first place, because the basis of Relativity is that it's both. The equivalence principle means no preferred reference frame. The only semblance of a preferred reference frame in this case is the fact that, given the gravitational potential as a tensor field in GR, the clock at the greater potential runs slower.



posted on Sep, 25 2011 @ 09:11 PM
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reply to post by Arbitrageur
 



Einstiens work, prtained too this galaxy.

not this universe.
that is the problem,
when you change,
universes,
where
there are, two,
time waves.
or surfers.
or



posted on Sep, 25 2011 @ 09:39 PM
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Originally posted by BobAthome
Einstiens work, prtained too this galaxy.
not this universe.
that is the problem,
when you change,
universes
Where did you get the idea Einstein's work didn't apply to other galaxies?

Regarding other universes, I know some people believe in them.

Other universes, like flying spaghetti monsters, may indeed exist. All that's needed to confirm their existence is some proof. Until we have proof of either one, how can I give any preference to your suggestion it's got something to do with another universe, over someone else's suggestion it's got something to do with flying spaghetti monsters?



posted on Sep, 25 2011 @ 09:56 PM
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reply to post by Arbitrageur
 


seperate our galaxy

from the Universe.

after all,would Galleo been crusified by the church,,had he said,
In Our Galaxy,,
the
Earth is Centre.??

now reverse everything i said,,

gallaxy/universe.
and who fought for what idea.

edit on 25-9-2011 by BobAthome because: (no reason given)



posted on Sep, 25 2011 @ 10:05 PM
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I'm pretty sure Dingle's question was already answered mathematically.
I believe its refered to as the Dingle Berry equation.
edit on 9/25/11 by AstroBuzz because: (no reason given)



posted on Sep, 25 2011 @ 10:32 PM
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reply to post by BobAthome
 

You're not making much sense. You're talking about roughly three centuries ago, and even as little as one century ago when Einstein wrote his paper on special relativity in 1905, there wasn't much distinction between a universe and a galaxy in the minds of scientists.

If they didn't understand the distinction when Einstein wrote his special relativity paper in 1905, they certainly didn't understand the distinction in Galileo's time. It wasn't until 1912 we got the first measurement that implied nebulae might be other galaxies, and then from 1920-1930 there was more and more proof that some nebulae were other galaxies.

Also, Galileo was never crucified, he was sentenced to 3 years in prison and to renounce his heresy.

Here is the English translated version of Einstein's paper on special relativity:

www.anu.edu.au...

I searched the entire document for the words "universe" or "galaxy" and there is no mention of either one. So it seems to me you are arbitrarily inventing some scope of applicability for the document where no such scope is claimed.



posted on Sep, 25 2011 @ 10:38 PM
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reply to post by Arbitrageur
 


"Also, Galileo was never crucified, he was sentenced to 3 years in prison and to renounce his heresy. "

3 years in prison ,,,,Galileo was never crucified,,,ya right!

3 years in prison piece of cake i guess.

"I searched the entire document for the words "universe" or "galaxy" and there is no mention of either one."
ok my appoligies,, guess they didnt exist ,,at that time,,

edit on 25-9-2011 by BobAthome because: (no reason given)



posted on Sep, 26 2011 @ 12:03 AM
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I read the linked PDF.

Yes, Dingle's Question has been answered.

You get symmetry in identical reference frames. When one accelerates (as would be the case in all of Dingle's examples) and the other does not, they can be physically distinguished.

Why? Mount an accelerometer and record it. This can be done with local physics.

Take two clocks, have one go in the circular path and meet up back with the other one. (This is one of Dingle's questions). The local physical effects enjoyed by them are measurably different: one made the accelerometer trace squiggle and the other did not. Hence, they are distinguishable and there is no paradox. I learned this in freshman physics. (it's the same as the 'twin paradox'---one had to accelerate and the other didn't).

The principle of equivalence used by General relativity extends this to gravitational fields, so that particles inside gravity wells age differently from those outside of it. The corollary (gravitational redshift) is an experimentally measured fact, seen in a very famous (and very clever) experiment using some remarkable QM properties to get a very sensitive measurement.



posted on Sep, 26 2011 @ 01:00 AM
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reply to post by mbkennel
 

Great answer.
I agree with pretty much everything you said except the part about Dingle's question being answered.

To explain what happens in accelerating inertial reference frames, requires that general relativity be invoked. Dingle (and apparently also the author of that pdf) insist that general relativity can't be used to answer the question, and that it must be answered only with special relativity.

So I maintain that given Dingle's (and McCausland's) constraint that the question must be answered with special relativity, the question is not a valid one and can't be answered with special relativity, because it's a general relativity question, not a special relativity question.

To rephrase the question, what Dingle is asking is: "Please answer this question, which I won't admit requires general relativity to answer, and answer it using special relativity. I will not accept any answer that uses general relativity (even though it's really a general relativity question)"

So from that perspective, one might say the question is NOT valid, and is therefore impossible to answer to Dingle's satisfaction, because he (and McCausland) won't admit the question is really a general relativity question.
edit on 26-9-2011 by Arbitrageur because: clarification



posted on Sep, 26 2011 @ 02:18 AM
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reply to post by Arbitrageur
 


Bit gobbledegooky there op.
Quick and simplified answerin laymans terms is that the clock at equator will run more slowly due to slightly
lower g and higher linear velocity regardless of the frame of ref



posted on Sep, 26 2011 @ 03:45 AM
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I have my own theory on this, I will post it someday.
To my knowledge it has not been answered satisfactorily and will not be until scientists think out of the box.

The best answer as of now is the one that has accelerated. That answer is not good enough. For those who think it is answer the following.

Two spaceships start off from two different planets a few light years apart (going in a straight line to each others planet). They accelerate at the same rate of acceleration until they reach a pre-determined velocity (say 0.2c). When they are at the velocity of 0.2c with respect to their starting planets, they are moving at approx 0.38c relative to each other. So which clock is running slow?



posted on Sep, 26 2011 @ 04:18 AM
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Originally posted by Angelic Resurrection
Bit gobbledegooky there op.
Quick and simplified answerin laymans terms is that the clock at equator will run more slowly due to slightly
lower g and higher linear velocity regardless of the frame of ref
Wrong.

Lower g's don't make a clock run slower. They make it run faster. But don't feel bad. A NASA astronaut wrote a blog and he wrote the wrong answer too, because he was confused about whether his clock would run faster or slower as he didn't get the fact that the time dilation effects of higher velocity and lower gravity are in opposite directions and partially cancel each other out, nor did he understand the direction of the dominant effect in orbit. So if a NASA astronaut gets it wrong, I guess you shouldn't feel too bad about making the same mistake.

The velocity effect is dominant on the ground, and the lower g effect is dominant in typical low earth orbit. Here is a plot of the magnitude of the opposite directions of time dilation for geostationary orbits:

www.thescienceforum.com...

The blue line on the bottom shows that velocity makes the clock run slower. The green line at the top shows how above the 0 line, (corresponding to above the Earth's surface), lower g's make the clock run faster. The red line in the middle, is the difference between these two opposite effects, at various altitudes, and it shows how the velocity effect is dominant at the surface, making the clock run slower, and the gravitational effect is dominant in orbit, making the clock run faster. In fact where the red line crosses the horizontal zero axis, the clock will run neither faster nor slower

Velocity does make a clock run more slowly. While you got that part right, you're missing the point about the velocity of a clock at the equator. It's not linear. Linear means a straight line. The surface of the Earth is curved. Therefore it's moving in a curved motion, not a straight line motion, which means it's experiencing acceleration. That's why physicists invoke general relativity when they calculate what a clock at the equator will do, but Dingle won't accept any answer that uses general relativity in the explanation.



posted on Sep, 26 2011 @ 04:42 AM
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Originally posted by kaleshchand
Two spaceships start off from two different planets a few light years apart (going in a straight line to each others planet). They accelerate at the same rate of acceleration until they reach a pre-determined velocity (say 0.2c). When they are at the velocity of 0.2c with respect to their starting planets, they are moving at approx 0.38c relative to each other. So which clock is running slow?
You can answer that question from 3 reference frames, which I'll call A, B and C.

And let's assign arbitrary headings. In reference frame B the spaceship captain is going "east", the C captain is going "west".

A relatively distant observer, to the south lets say, call him "A", is so far away that they observe the distant clock movements from B and C as relatively symmetrical.

So the three answers from the three reference frames are:
B will see C's clock run more slowly than his own.
C will see B's clock run more slowly than his own.
The distant observer, in reference frame A, will see the clock movements from both B and C move slower than his own, but in comparing B to C they both move slower by equal amounts because of the symmetry with which you set up the thought experiment.

Since there is no preferred frame of reference, the observations from any of the three reference frames are equally valid. But observer A will neither see B's clock going slower than C nor vice versa. If they are going the same velocity relative to A, their clocks will move at about the same rate from A's perspective.

Isn't this fun?
edit on 26-9-2011 by Arbitrageur because: clarification



posted on Sep, 26 2011 @ 12:20 PM
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Originally posted by Arbitrageur

Originally posted by Angelic Resurrection
Bit gobbledegooky there op.
Quick and simplified answerin laymans terms is that the clock at equator will run more slowly due to slightly
lower g and higher linear velocity regardless of the frame of ref
Wrong.

Lower g's don't make a clock run slower.


Wrong. Chk out the graph on the link in my signature.



Velocity does make a clock run more slowly. While you got that part right, you're missing the point about the velocity of a clock at the equator. It's not linear. Linear means a straight line. The surface of the Earth is curved. Therefore it's moving in a curved motion, not a straight line motion, which means it's experiencing acceleration.


Lol linear means the tangential velocity here and besides both the clocks experience equal accel.

Hope that helps



posted on Sep, 26 2011 @ 02:14 PM
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Originally posted by Angelic Resurrection

Lol linear means the tangential velocity here and besides both the clocks experience equal accel.


"Linear" never ever means tangential velocity under any circumstance. Tangential velocity is the point velocity of an accelerating reference frame at any given instant. If velocity is linear, it has no tangent. The two are mutually exclusive.

Also, both clocks are certainly not experiencing equal acceleration.

Lol



posted on Sep, 26 2011 @ 02:29 PM
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reply to post by Arbitrageur
 


Your answer is partly correct, The stationary observer would see both clocks running at the same speed. The ships would also see the clocks running at the same speed. Though I have no idea how one would see a clock in another spaceship.


The reason being if they slowed down and became stationary relative to each other at the point where they crossed and compared clocks they would find both the clocks having the same time.

The problem here is that it is said that velocity slows or speeds up time. But it does not. Velocity does not affect time in any way. Acceleration does, and velocity is merely an effect of the same acceleration that is also affecting the clocks, it is not the cause of it.



posted on Sep, 26 2011 @ 04:36 PM
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Originally posted by kaleshchand
The problem here is that it is said that velocity slows or speeds up time. But it does not. Velocity does not affect time in any way.
Here is what Einstein said about velocity affecting time when he explained special relativity:

www.bartleby.com...

Every reference-body (co-ordinate system) has its own particular time; unless we are told the reference-body to which the statement of time refers, there is no meaning in a statement of the time of an event.


He is speaking about two reference frames moving at a linear constant velocity with respect to each other. And he says that each reference frame has its own time.

So are you saying you're right and Einstein is wrong?



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