Right Hand Rule - a question

[Nesti]

Is there a particular reason why the Right Hand Rule exists...ie viewed from in front of a current flow, the field generated rotates counter-clockwise...why is it right over left, or, why wouldn't the field oscillate back and forth (left to right, back to left and so on).

[mithrandir]

It's a convention. Thumb points in the direction of current (conventionally positive to negative). Fingers in the direction of the field (conventionally north to south). Switching one of those conventions, but not both, would give you a left hand rule.

With DC the current direction doesn't change, so the magnetic one doesn't either.

If the wire is carrying AC the electric and magnetic fields reverse together, but I seem to recall 90 degrees out of phase.

[Jarvamundo]

Correct, Alternating m-field comes from alternating current.

Re 90 phase? Where electric strength and magnetic strength are always perpendicular, and always meet at zero. ie. where there is current there is always magnetism, vicer versa, see Maxwell's Laws.

Also important to think of the magnetic field as a fog (vector field). NOT lines (lines are just an easy way to quickly draw a field, like topographical lines to a mountain/valley.... they don't physically exist).

[gary]

If the question were "why does a magnetic field obey the right-hand rule,
rather than a left-hand rule, when a current flows through a conductor?", then as
the previous two respondents have noted it is a convention and because
most Electrical Engineers, including the one that formulated the right-hand
convention in the first place, are right-handed. (Though I personally know some
who are left-handed and still managed to graduate). :lol:

In other words, there is nothing "magical" about the handiness.

The relationship between an electric current and a magnetic field (i.e.
electromagnetism) was originally put forward by Ampère but it took Maxwell to
formulate in terms of field equations.

[Jarvamundo]

heheh.. and Flemings right hand?

"the direction of the magnetic field (counterclockwise instead of clockwise when viewed from the tip of the thumb) is a result of this convention and not an underlying physical phenomenon." from wiki

(the hand of god could still be left)

[Nesti]

Hang-on-hang-on, I'm still unsure as to why nature's disposition ("convention") on electromagnetism didn't go the opposite way, and that science's understanding didn't produce a left hand rule instead of the right hand rule.

I understand that theory is governed by observation, and theory tries to explain trusted tendencies (laws), but what if 150 years ago the observation were the opposite; what if a current produced a clockwise rotation if viewed from downstream (a left hand rule)? Conversely the current left hand rule would simply be replaced by the right for those applications they pertain.

My question really is, why is there a lopsidedness? Get what I mean, or am I missing something obvious here?

Further, I would completely understand if the old idea of an Ether Wind existed, then - as with Coriolis Effect - there would be a simple answer...a left hand effect or a right hand effect could be attributable to the angle a field was relative to an ether wind, but the ether wind [apparently] does not exist. So, I'm just confused as to why it is right is favored over left.

:scared3:


I'm right handed, but I fly with my left hand. What does that mean?! :P

[avandonk]

It is just a convention so all the signs are in the correct direction.

Real current is the flow of negatively charged electrons yet we still stick to the convention that current flows from positive to negative.


Think about X, Y and Z cartesian coordinate system. This also follows the right hand rule for obvious reasons.

Cross products in vectors also come to mind.

In a mirror Universe the left hand system would be just as valid. Consistency is the only consideration.


Clockwise derives its direction from sundials in the northern hemisphere.

In the southern hemisphere sundials run anticlockwise.

Bert

[mithrandir]

In the northern hemisphere winds around high and low pressure systems follow a right hand rule. In the southern a left hand rule.

Make a fist using the appropriate hand with thumb out.

Low pressure means rising air. Point the thumb up.
High pressure means descending air. Point the thumb down.

Winds will rotate in the direction of the fingers.

Of course left, right, up and down are all just conventions too.

[Nesti]

This statement you made Bert I think highlights my point.

I guess it's like flipping all charges in the universe; so long as they are all reversed with equal value - your statement "consistency is the only consideration" - at the same time, there should be no change in the overall structure of the universe; it's conventions are simply flipped.

But I'm still left with the same issue in my mind; why are the "conventions" the way they are...probably too big-a-question to answer.

To me, sundials and wind directions are all perfectly explainable in the context of earth's rotation with respect to a northern aspect versus a southern aspect (Sundials), and movement with respects to mass distribution (coriolis)...these are not a mystery. Even the idea that matter succeeded anti-matter has some logical behavior...but a 50/50 coin toss of a right handed universe over a left handed universe gets me.

The simple notion that the universe (at least some of it's properties) could have been different, without conflict, presents some deeper questioning.

Cheers

[avandonk]

I should have said mirror convention universe. Left or right handed is arbitrary. The conventions have to be a mirror image to still be consistent. Vector algebra makes this more clear.

bert

[erick]

For some unknown reason, life on earth has based itself on amino acids that are (nearly) all "L" stereoisomers - sort of a left (or right) handedness in chemical structure. Why? Don't really know.

[gary]

I think you will find that, indeed, it is "too big a question to answer" today with
any certainty based on current knowledge and will probably be linked to the
formation of the universe during the very early stages of the Big Bang itself.

As you allude to, it is possibly related to aspects of the Big Bang epoch
such as matter-antimatter asymmetry that took the Universe, that we know and
love today, in one "direction" rather than the other. Much has been theorized and
written about why this may have been and quantum fluctuations during the
inflationary period may be at the heart of it.

This field of physics is evolving so rapidly that perhaps someone who tries to
keep abreast of the literature may have a better response to the one I have
just provided above.

[supernova1965]

Could it be that the majority of people who view these phonema are right handed which influences their preceptions.:confused2:

[sjastro]

Parity (spatial coordinate flipping) is conserved for gravity, electromagnetic and strong forces. Not so with the weak force.

A mirror Universe would be a very strange place, if it was able to exist.

Regards

Steven

[Nesti]

Spoil-sport! :P

[circumpolar]

Youtube.
Electricity & Magnetism Hand Rules (part one)

http://www.youtube.com/watch?v=9Zy0VHBXxLU&feature=fvw

Just one of many.

[sjastro]

Here is parity explained ;););)

http://users.westconnect.com.au/~sjastro/Tutorial/parity.jpg

[snas]

The right hand rule does not only apply to electromagnetism etc as have been discussed here. It also applies in chemistry and biology. As has already been pointed out here,most people are right handed. DNA is a right handed double alpha helix. Organic molecules such as glucose etc etc can have either right handed or left handed versions. Right handed versions vastly predominate over left. In fact, some organic molecules have vastly different properties between the right and left handed versions to the extent that if the left handed version was the predominant version, the biology of Earth would be quite different.
Stuart

[Nesti]

Geez Steven, that's really cleared it up for me. :help:

"suggest[ing]...that space has a kind of twist"...now that statement pretty much intersects my original question...space having some sort of disposition or tendency for right handedness.

Reason?

Well, without trying to come-off too Mung-Bean, let me point out that ancient energy therapies - don't roll ya eyes just yet people - have EXACTLY the same right hand convention for building and purging Meridians channels (as in Acupuncture, Acupressure etc)...and ALL modalities are the same, no matter their origin (Egyptian to Mayan). 50/50 chance of being right or left maybe, but throughout so many modalities spanning the planet and thousands of years? Surely one must have been left handed?...It doesn't seem so!

So, we see right handed conventions in two totally separate systems of thought and belief, not just different disciplines in science. One known for a couple of hundred years, the other known for several (4 to 5) thousand years.

I'm not saying anything's connected, just pointing out a simple well know fact.

[Jarvamundo]

ohhh "space" having a twist... this will get interesting... gravity-only is going to struggle here...

Should have a squiz at Bryan Gaenslers (USYD Astronomer Prof.) Magnetic Universe work... interesting stuff.

[sjastro]

"..... it upset the conservation of parity P, which assumed the symmetry of the Universe, and suggested instead that space has a kind of twist"

The trouble with references like this is that since it is written for the general public (a Time Life book on scientists), the terminology can be very sloppy.

The violation of parity doesn't prove "that space has a kind of twist" at all.

Regards

Steven

[Nesti]

Wasn't the author using the term "space" as a general term anyway?! I mean, he wasn't inferring that the spacetime continuum had a twist, or that GR needed refinement...he could just of easily used the words, universe or cosmos. That's why I chose the term lopsidedness (room for escape).

Hang-on, you introduced it in the first place...So by association you must take responsibility for;

Crack-Pot Index
2 points for every statement that is clearly vacuous :P


It's only fair! :lol:

[sjastro]

Nothing vacuous about it at all.

In the context of this thread parity is not even a measurement of lopsidedness.

It is a property of the spatial flipping of a quantum wavefunction or state, not the Universe, cosmos, spacetime etc.

A quantum wavefunction or state can have either have an odd or even parity. If the wavefunction or state changes through a process of say particle decay or collision between particles, parity is either conserved or it isn't.

For example if the initial state has even(odd) parity and the final state has even(odd) parity then parity is conserved.
If the initial state is even(odd) but the final state is a combination of even and odd states then parity is not conserved.

Where parity is conserved you can spatially flip the wavefunctions as the process can proceed irrespective of whether left hand or right hand particles are involved.

Processes involving the weak force cannot be flipped as the final state is a combination of even and odd quantum wavefunctions.

Regards

Steven

[Nesti]

I was referring to the Author's comments; the terms "space" and "twist" in the attached quotation, not the concept of Parity or associated math. :)

Cummon, take the points, "turn to the dark side Luke".

[Jarvamundo]

The question resonates with me Mark... often ponder about the beauty of fractals (http://en.wikipedia.org/wiki/File:Phoenix(Julia).gif) and particularly the scalability... often sttttrrruggle with gravity "the force" ;) as the dominant explanation for the largest scale of what our eyes see "the twist", when it (gravity) doesn't even get to sit on the bench and "cut the oranges" for the team (of forces) at lower scales.... probably something for another thread... but resonates with the "whys of nature" direction of your question and how EM participates in fractals (http://en.wikipedia.org/wiki/File:Square1.jpg) and the useful technology recently developed (fractal antenna) (http://en.wikipedia.org/wiki/Fractal_antenna) from exploring this natural phenomena....

I sense a disturbance... natural philosophy is meeting maths here...

take the points, cmon over ;)

I'm enjoying both your posts and discussions SJ & nesti... a credit to this forum.

[Nesti]

Thanks Alex. The one which really gets me, is Young's Double Slit Experiment. But not the usual mystery everyone else seems to focus upon; I don't really care which slit the particle goes through as that's a property of the quantum world, and I can accept that (as most other theories)...the mystery for me isn't super-positioning of states, it's why does one individual particle land in one particular position and not some other position, within the darkening region (interference pattern or not)? How are all the particles distributed in accordance with a particular function? For me, this seems to be related to why event outcomes can be different even though the experiment is identical...even bigger is the question of why does one event go one way in particular? Is it balancing something about the universe - but that would infer knowing, and that's a violation of SR.

ie In the Double Slit; why does a the particle land somewhere in the left band rather than the right band, and vice-versa. You can apply that question to all the bands within the interference patten also.

To say that it is a product of a wave function is fine, and I get that, but that infers guidance, and guidance infers structure and order.

What structure, what order? These are my questions.

[Jarvamundo]

Watching photon by photon coming down and "deciding" where to land was an amazing thing to observe... I loved playing around with this experiment at uni... boggled me endlessly. There are some great photon by photon videos around.... brain = ouch! My studies into this have leant me more towards "things" propagating as a wave with a photon representing a point of measurement, not something physical... bit hard to wrap it up here in a post... but more down the line of questions "what is a wave, what is a photon, what does it travel in"... a deep rabit hole towards what is the "speed of the message" . Violating SR is a restriction constantly faced.

I do shy away from "guidance", I'm leaning towards a higher level of nature of which we are seeing the averages of. Thinking more along the lines of SR violation here. SR aside (please dont hurt me SJ), my point here is, I get very uncomfortable with guidance, intelligence, plan, order, as these throughout history have been consistently created to explain the higher level we are oblivious to at that point in time.

You're leading me towards a high score on SJ's card! You going to go 1/2's in my points? haha I can send you a loooong list of my questions, I am encouraged by healthy nature of yours. Good scientists are directly inspired by this type of natural philosophy, numbers are dwindling with the call to young folk being "just solve this last equation and we're all done".

i'll shut up now... we are straying from the thread.

gimme the points

my question: "Is one able to assign their own points? or is this subject to peer review?"

[Nesti]

It's not really straying because I posted Young's experiment for a reason, ie a suggestion that particles being guided into position in order to ensure a stable reality, versus, a suggestion that there is pure particle randomness trapped within the confines of a wave equation...and that either one could demonstrate 1. a strict structure/order, or 2. a looser structure/order...I say the terms structure/order simply because when I look out my window at the world, I don't see chaos, I see structure, order, and perhaps remnants of deterministic chaos at far smaller scales.

The connection to the Right Handedness (convention, parity whatever) of the universe, in that, is there a particular way the universe goes about its business. Something which brings about a stable reality, or better yet, something which is conducive to stability...might symmetry be insufficient or non-conducive in creating stability within the universe...this would perhaps explain why the 'Standard Model' of Particles is the way it is and why we have so many of these conventions along the same behavior. OR, perhaps it's simply pure chance combined with how things dynamical fit under stress.

I know these are all out-there ideas and suggestions, but there's enough intelligent people on this forum to understand the sheer implications of what the questions pose in-themselves.

[Jarvamundo]

Yes! Couldn't agree more. I see evolutions of systems, organization, structure and resonance. However often vastly at odds with the requirements of the standard rule set and accompanying explanations, this can be confronting when attempting to seriously discuss.

[Nesti]

True, but at the end of the day, this is simply a forum, and forums are for discussions. You could easily enforce restrictions to discussing what is popularly supported or that which you can make reference too (data)...but how many people would be here?!

Just be mindful that most people are fascinated not by numbers in mathematics, nor the data in science. They are in fact fascinated by the relationship between the numbers in mathematics, and the relationship between data in science.

Similarly, many people (as I am) are fascinated in the relationships between what we see and experience directly, and how science and philosophy connect to them. I feel the desire to know such details rests in the desire of the individual to understand the connection between themselves and the big picture.

The Right Hand Rule is simply piece of an overall puzzle, but the implications of a convention, or parity are far greater.

[Jarvamundo]

Might i suggest looking into lenz' law... it has to do with the resistance of change of magnetic flux or "opposing change".

"An induced current is always in such a direction as to oppose the motion or change causing it"

(sorry took me a bit to recall... wasnt sitting right with me... direction is also covered here... hope this helps )

but yeah from there we are getting down to physical characteristics of our universe, use ya left you get the force on ya thumb, use your right you get the current etc. but this resistance to change is the whole reason we are here, conservation of energy etc... otherwise it would be a runaway...

[Nesti]

Stuart, a Chemistry teacher from Monash resigned to take a position with us here in Perth. He's teaching Organic Chemistry as part of our Herbal Medicine course (I'm sitting-in for RTO stuff). We covered it today, and you're right about the L and D Glucose molecules...when we produce them in the lab we get a 50/50 split between the L (left) and D (right) Glucose molecules, but in nature it's almost always D-Glucose (right).

There's actually a tonne of stuff in organic chemistry which has a heavy right foot.

[renormalised]

Here, I'm going through a huge spanner in the works....what's wrong with having an intelligence behind it all. Regardless of how "unsound" and "religious" it might seem, having some sort of higher sentience/intelligence behind the works doesn't mean it has anything to do with religion, or faith or anything else. It's just a natural part of the order of things. Just because it feels "unscientific" and that you have no empirical evidence for its existence, doesn't mean it's a load of crock. Maybe you do have all the empirical evidence you need, you just can't see the forest for the trees. Or, you don't have the means to prove either way because you don't have the tech to do so, as yet. Yes, it may not exist, but we just don't really know...do we :) But, then again, maybe we do know it exists but just don't want to accept the possibility because in our head long rush to become smarter and more enlightened, we've actually lost sight of the most important aspect of the whole exercise of wanting to learn more and become more knowledgeable....to become more enlightened :)

You can learn much, but still know very little.

[Jarvamundo]

all sounds cute... but i'm still pretty pissed i don't have a hoverboard yet...

I don't see how this is guna get me one...

It's still the whole plan yeah? hoverboards for everyone right? They lied to us! This was supposed to be the future!
http://vimeo.com/8661544

[renormalised]

Just a few more years, and you'll get one :)

Just need a small enough power source :P

[avandonk]

We were just contemplating the rules for electromagnetism and their concomitant forces not the parity of the Universe. It is just a convention so your electric motor rotates in the direction your customer wants.

Bert

[avandonk]

If you all think that Young's experiment is counter intuitive. It has been with done with Buckyballs C60 going through two slits as a wave function and then producing a diffraction pattern wth itself! It is really a measure of reality. Nothing actually exists as matter, just wave functions until it interacts. All possible paths are being followed until you take a peek and then the whole lot collapses into your reality. A bit like when you check to see what your kids are doing.

I don't really exist until my next post!

As for an intelligence behind it all in the words of John Mackenroe? ' you gotta be kidding!'

It is our puny animal minds where a hierarchy exists in our very primitive social order that a natural extrapolation comes up with a mythical being with more power than the alpha individual. Generally a psychopath. Hence all the fire and brimstone through a lot of history.

Resorting to any sort of mythical intelligence to explain the unknown is a major itellectual copout. Feeble at best misinformed at worst.

Bert

[Geoff45]

I think what Mark is getting at here is something like the following. Electrons moving along a wire from A to B produce a certain magnetic field--call it MA. If the electrons go from B to A they produce a magnetic field in the opposite direction--call it MB. These are all perfectly concrete testable phenomena and have nothing to do with convention. So Mark's question is why did the electrons moving from A to B produce MA rather than MB?
Geoff

[adman]

This whole thread seems to have missed the point to me. It started off with a question about the right-hand rule and why the field is generated in that direction rather than the other. Then others chimed in about how there is a whole lot of right-handedness in nature and this was extrapolated to there being some guiding intelligence behind the workings of the universe....

Now as far as i can see there is only one connection between the handedness of glucose isomers, the direction of a field generated by an electric current, the direction water goes down a plughole in the southern hemisphere and the swirl of hair growing on the back of your head - and that is the human being that has named them as right handed. *

You can't compare such disparate structures and say there is some unifying power behind their right handedness because it is just a human way of describing them. No more, no less. There is nothing inherently right handed about the D-isomer of glucose, (they could just as easily have been called Isomer Type 1 and Isomer Type 2) and the only thing right handed about the DNA helix is the fact that it happens to rotate the same direction as the radius and ulna bones in the human forearm when you supinate your hand!*

The original question about why the field goes one way and not the other around an electric current is meaningful - but at the moment the answer is "that's just what it does".

Adam *

[mithrandir]

Back in the mists of time near the start of this thread, several people including me, said it was all to do with conventions.

By convention, electric current goes from positive to negative. The fact that electrons go the other way is immaterial.

By convention, magnetic fields curve from north to south.

It comes down to whether the conventions were made up to suit a right hand rule, or someone noticed that a right hand rule fitted the conventions.

Reverse the electric current convention and retain the magnetic field one and you get a left hand rule.

Reverse the magnetic field convention and retain the electric current one and you get a left hand rule.

Reverse both the magnetic field convention and electric current one and you get a right hand rule.

[adman]

yes- there were a few voices of reason early on :)

[sjastro]

Mark,

With regards to your original query you should employ "puddle thinking" to give you the answer.

". . imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be all right, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for."

This is Douglas Adams taking the mickey out of the Anthropic Principle.:)

Steven

[Jarvamundo]

This is the whole quantum mechanics vs classical "field" physics dilemma, cause and effect with c as the limit.

I agree, i'm with you on the, the field propagates as a wave or field, and is 'measured' as a photon.

As you've pointed out, the role of the observer effects result, also the how the effects of the observer can effect the probability of result, seemingly beyond the limit of c SR. Of which is address in GR no? I've got some cool videos somewhere on these experiments...

Resident well versed relativist SJ is probably best to comment here...

The weirdsh#tometer continues to bend the needle.
http://www.scientificamerican.com/blog/60-second-science/post.cfm?id=quantum-weirdnes-wins-again-entangl-2008-08-13

[renormalised]

Looks like that weird fecal matter-o-meter has hit the site....they're down and out at present :)

[Jarvamundo]

you obviously affected the result by 'observing' carl... it's back up now...?

Nature link here if need be: http://www.nature.com/nature/journal/v454/n7206/edsumm/e080814-10.html

[renormalised]

Did you read the last sentence in that blurb about the experiments??. Basically what they're saying is this...they found, in their experiment, that the lower limit on the speed of quantum entanglement is at least 10000c. Therefore (and taking into account SR) it can't happen in nature. What a ridiculous statement!!!! If they were testing QE in this experiment, then how in the hell could it be a "hypothetical" spooky action if that's what they were actually testing between two particles, or whatever they were testing. It's only hypothetical if it's modeled in a computer simulation or simulated in some other fashion....not actually put to the test. They just don't like the results they came out with to be something which could occur in nature because the great god Einstein says it's not possible. Or the fact he didn't like it and didn't really understand it.

That's what annoys me...scientists wanting to hold onto cherished notions even when experiments/observations fly in the face of those notions. It's alright saying "but it holds up under every other thing we've done and it works...blah blah blah", but when something comes up which says otherwise then they've got to find all the excuses to say it's not going to happen...even if they actually see it happening.

[Nesti]

A song from the Goodies might be timely, "String-string string-string, everybody loves string" :D

[Nesti]

Well Steven, we seem to have come back to opinion and belief again, in that although all must agree that there is indeed determinacy within the universe - as there is predictable structure - but to what level it's expanse is unknown. Is it a determinacy/randomness/probability mix? Is it completely deterministic? We may never know.

Personally, my belief is that randomness and probability do not exist; they are akin to chaos theory before deterministic chaos. Chaos being a misnomer, which ultimately turned out to be just another gap in our understanding of the universe itself.

I also believe that 'Time Asymmetry' has a role to play, not in a classical sense, but in a QM and Relativistic sense. I believe that Action at a Distance can, and does, harmoniously feed into particle behavior, and that-that behavior is guided...not by any God related Mumbo-Jumbo, but by Time Asymmetry, whose sole purpose is to create that "Stable Reality" I keep mentioning about. Why is it that two completely identical experiments can produce vastly different outcomes? Is it simply a counter-intuitive property of matter at the QM level and completely normal, or is it perhaps the smoking gun of a type of particle time asymmetry, positioning the pieces of the dynamic puzzle at each and every moment in time and space, to ensure that stable reality actually becomes the reality. Such a protective property would be conservation of information and energy at its' finest...think about it for a minute. Particles which we think move and behave in mysterious ways could possibly be the outcome of a time asymmetric property of matter...and String Theory might just allow that through higher dimensional space, where SR might not be violated.

In this way, the Stable Reality removes the Puddle Thinking analogy altogether, and bypasses the entire argument.

Douglas Adams voiced his opinion in that analogy...no...he actually voiced his personal belief.

Cheers

[Jarvamundo]

Or c aint the limit

Time doesn't slow down, its the clock

Dingles Question

[Nesti]

I disagree with this entirely...nothing happens to any of the clocks in uniform motion, nothing! It is the space and time in which the clocks' resides which changes, certainly not the clocks themselves. Space and time are flexible, not clocks or even trains. This is why tidal forces occur in bodies within a gravitational field; converging frames of reference cause bodies to converge, collide and/or create stresses on molecular bonds. Matter is not changing, the space and time in which matter resides is forcing change...but matter itself creates the properties of the space and time in which it sits...weird!

If the universe were completely empty except for two clocks at either end, billions of light-years away, with no possible way of comparing relativistic events, even through interactions of light, and if these two clock were moving in opposite directions, not knowing which one was really moving (which is a mute point anyway), I believe that there would be no distortion of space and time as there has not been, and cannot be, any interaction. Bring those two clocks close enough for light to interact, and relativistic effects would immediately become apparent (albeit at c).

I feel that the universe is built upon the properties of light, and that light, in fact all matter, carry information in the form of frequencies, and these frequencies can create energetic connections (entanglement) between two separate frames of reference, and these can remain connected until the frequencies are changed (disentanglement); this is yet another reason why String Theory offers me a great deal of logical reasoning, holds the promise of merging relativity with QM.

I know these comments are not verifiable, but that's why I used the words "feel" and "believe"...but nobody knows the truth anyway.

[sjastro]

This is not even original, it's simply the twin paradox.
The moving clock will run slower.
The key to the problem is that the moving clock needs to be returned to it's original position in space (not space time) in order to compare the times elapsed on each clock. This destroys the symmetry aspect of the paradox.
The stationary clock's world line "moves" along a straight line in space time (along the t-axis), the moving clock moves along an oblique worldline (including the t and x axis) but inside the light cone of space time.

Here is the full explanation involving Minkowski space time diagrams.

http://en.wikipedia.org/wiki/Twin_paradox

Regards

Steven

[circumpolar]

Another way to think about it is that one clock must be under an acceleration (either + or -). This breakes the symmetry.
If both clocks experience the same accelerations then the symmetry between them remains.

[sjastro]

Correct. Einstein also argued that the moving clock when under acceleration would undergoe gravitational time dilation via the equivalence principle.

Regards

Steven

[sjastro]

The editor's summary is woefully inadequate.
For example what is the exact nature of the test?

From what I have seen in one of the attached summarys it appears to be yet another photon polarizing test.

If so then Bells inequality is violated, there is no communication faster than light because there is no communication between the photons in the first place.

It is the No Communication thoerem at work.
http://en.wikipedia.org/wiki/No-communication_theorem

Regards

Steven

[Jarvamundo]

So with reference to this twins paradox thought experiment?

How does this differ from the aether style definition, of the moving clock moving through the aether (light carrying medium) and the clock it'self slowing down, because the matter in the clock (electrons, etc etc etc) have to travel further, therefore appears to have 'slowed time'?

[renormalised]

I only had the chance to read the summary (didn't want to fork out the money to buy the paper!!...or go through the uni to get it :))

I'll have another look later :)

[renormalised]

You know, when all things are said and done, does the right hand really know what the left hand is doing?? :):P

[Robert9]

As best I can recall, given that it is more than 50 years ago since I studied Form 5 physics, the direction of the magnetic field was related to, or perhaps defined by the direction of the deflection of a compass needle placed above the conductor. Or have the years befuddled my aging brain - which would not surprise me!:question:
The use of the hand just made a convenient method of remembering which way things went.

Robert