Have the Pioneer anomalies also affected other probes?

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Offline yor_on

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Have the Pioneer anomalies also affected other probes?
« Reply #50 on: 27/04/2011 15:32:11 »
I do agree on "gravitational time dilation as a very real, observable and quantifiable effect." Mike, as described when measuring between frames of reference. To really show it you need a 'twin-experiment' though. And this is because only then will you be able to measure a quantitative difference between the twins, the traveling twin being younger biologically. What i don't like is the idea of it existing places where 'time' goes slower, and where as I understood you to put it before, time do so to to adapt to lights 'constant speed'.

As I see it, when you do so you redefine light as having different speeds but with 'time' now adapting itself to, more or less, fool us :) That's not how Einstein saw it, and it's not how I see it either. Light is the foremost constant I know, it has only one 'speed' and doesn't care about where it comes from. It can come from a black hole, a torch light in your hand, or a speeding rocket and hit your eye simultaneously, all three will have the same speed. And if you go those to three places you will find your own time durations, as measured by you, to be 'as always'. So, according to you, there will be nowhere that 'time' slows down, that is, you will not by any experiment made prove that idea. This does not mean that time on earth has the same 'durations'. There has been experiments done with extremely sensitive 'radiative clocks', where you by placing one on the floor and the other on a table being able to show a difference in their measure of temporal durations. But you do not , whether you stand up or lay down change anything about the duration that is measured for you. Your life expectancy will not become any longer by laying on the floor.

So your time will always be the same, but durations between positional systems in SpaceTime will differ when compared. And why they do it is because light only have one speed in a vacuum. And so the idea of gravitational time dilation becomes one where you only can get it confirmed by a twin-experiment, where there is a comparison done between two human 'systems' having a 'exact same' biological clock and a same temporal origin, being 'twins', one leaving to then come back again. But, none of those twins will ever have noticed time 'moving differently'. There's a difference.
« Last Edit: 27/04/2011 16:20:54 by yor_on »
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Offline MikeS

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« Reply #51 on: 27/04/2011 16:06:04 »
Mike, what I disagree with is that this is a science Q&A forum and your response to the initial question is based entirely on an unscientific guess.”

Rubbish, my initial answer was based on firm scientific proven fact.
General Relativity states that mass dilates time but that was not taken into account, hence the anomaly

“Your defense of your original answer isn't based on science either; it's based on your intuition.”

Rubbish, my intuition has told me to base it on known facts.  If you dispute this, tell me what I have said that is wrong.

“Why post this on a science forum if you aren't willing to engage with other posters using the scientific method of offering quantitative and falsifiable results?”

Rubbish, I am and have been more than willing, as evidenced by my posts in this thread, to engage with other posters.  Have any of them answered any of my points, ever? 

I have not proposed a new theory or new physics therefore there is absolutely no reason whatsoever to offer quantitative and falsifiable results.

What I have maintained is that the physics to explain the anomaly already exist but have been ignored.  This has so far been confirmed to be correct.  Virtually all of the points that I have posted have been ignored, not debated.  I have been continually miss-quoted by you, which I have mentioned before but none of that has been addressed 

You accuse me of bad science but really you need to look at a lot of what you have written, it’s mostly ideas and waffle and wrong

I have just written this before reading your last post which is mostly a load of rubbish.

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Offline JP

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« Reply #52 on: 27/04/2011 17:01:44 »
Well, Mike, I give up on trying to explain where you and the scientific method don't agree.  It's clear you have your own opinion and aren't willing to hear others.  It's a shame, because your point about time dilation was interesting, but the certainty with which you present along with your dismissal of the need for mathematics leads to a host of scientific problems with the idea and have bogged down any useful discussion.
« Last Edit: 27/04/2011 17:04:37 by JP »

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Offline yor_on

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« Reply #53 on: 27/04/2011 17:08:36 »
Mike, don't take our views to hard. You have what we might call a hypothesis. To prove it you need to create some proofs. That's what the math is for, I tried to look for your question and although I found, especially some Russian scientists that seemed to wonder in a similar fashion I found none asking the exact same. As you say, no matter how you and me argue, you base it on what you see as the theory of relativity which in a way is quite palatable to me :) I'm a avid fan of the theory of relativity myself, and you want to have it proved or disproved.

Well, then you need to do the math I think, because then you will have the definition laid out for us to look at. And your and mine discussion might or might not come in there, but I think we will agree on what math there is needed. Don't get all angry, Imatfaal is a very knowledgeable young man, and JP even more so. You need to remember that without any mathematical definitions it's awfully hard to 'count on it' and see if it will make sense. And you can't expect us to do the math for you, it's your theory and your math that should define it, not ours.

There are three different 'red shifts' in astronomy, Doppler, gravitational and cosmological (space expanding), and then above 0,4-5 'c' we find the Lorentz contraction expressing itself too. And all 'normal' photons you see are expected to come from exited atoms. Law of Energy Conservation and the Doppler Effect. It's a lot of math in that one but this one may be more palatable to start with Redshift components. And for those wanting a overview(?)

I guess some may want that, listening to the arguments. I find this one a very nice description of Doppler relative Lorentz contraction, making good sense to help one see the basic differences. C-ship: The Doppler Shift And JP I expect to know exactly what he talks about, when he doesn't he will tell you.
« Last Edit: 27/04/2011 17:13:15 by yor_on »
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Offline MikeS

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« Reply #54 on: 27/04/2011 19:47:44 »
JP,

I think it is a shame, none of you give any encouragement only criticism.  I have not had any positive feedback at all.  Yes I am confident that I have identified the source of the anomaly, but that's how I feel and I will have to deal with it if I am wrong.

I have never criticised the scientific method, it's essential in science.  I'm a firm believer in maths, as I said in a previous post but maths isn't the answer to everything.  I didn't think and I still don't think that maths is required to suggest what the reason is to explain what I consider to be obvious.  I sincerely believe that my explanation of the anomaly is the first thing that should have been considered to see if it explains the mystery.  The idea, it could be argued has little to do with science but a lot to do with common sense.  I have already reiterated on numerous occasions that I wish I understood the maths but I don't.  According to your reasoning that gives me no right to make any suggestions.  The world would be a much poorer place if everyone shared those views.  If you look back through all of the posts you will see there never was the start of any useful discussion.  There was never any feedback on the content and quality of what I suggested just a continuous stream of repeated attacks.

One question:-
It is known that gravitational time dilation is real and observable.  So it is known that any craft that leaves the Solar System will be affected by it.  What should have been the first suggestion to explain the anomaly?


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Offline Geezer

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Have the Pioneer anomalies also affected other probes?
« Reply #55 on: 27/04/2011 20:50:00 »
Mike,

I think it is necessary to quantify effects in science and, unfortunately, the only way to do that is mathematically. Also, math provides a common language that promotes common understanding in a way that spoken languages never do. Without some math to sort out the significant from the insignificant, we are liable to descend into acrimonious debates, QED this thread.

Perhaps we should lock this topic before matters deteriorate any further.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Democritus

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« Reply #56 on: 28/04/2011 05:42:29 »
"If anyone can prove to me for certain that the anomaly is not due to time dilation in the Solar System I would be delighted to hear from them." &
"I am absolutely certain that my original explanation is correct."
Mike

Would that I have such certainty!
I have been thrilled and astounded for a very long time now with the progress of science. If I have learned anything it is this:
As in love and war, and politics and life, so it is that nothing is certain in physics, astronomy and cosmology. [:)]

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Offline imatfaal

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« Reply #57 on: 28/04/2011 12:36:47 »
Mike - firstly keep it civil or one of the mods will lock the thread (btw prefixing every paragraph of a reply with rubbish is not imo civil). 

 I have just reread one of the papers by the JPL incl Turyshev - it details the methods that JPL use.  I can quite understand that it is difficult to grasp - but the calculation regarding gravity used various Parameterised Post-Newtonian Formalisms.  PPN is a method that directly engages with GR (as well as many other metrics) in situations where all speeds are significantly sub-luminal and the gravitational field is weak.  The measurement of the the light that you worried was not taking into account the gravitational potential time dilation/gravitational red-shift is calculated using the correct relativistic equations and comparisons with ephmeris time / barycentric coordinate time ie all times and rates are adjusted in terms of a clock outside the gravity well and is accurate to one part in 10^17.

That Turyshev says that the difference between Newtonian calcs and GR are negligable is due to the fact that both were calculated and the difference was negligible. 

These calcs are summarised at around pages 55-60 of the latest Tuyrshev article.  If you wish to continue the debate please engage with the previous paragraphs as they confirm to my mind that you have been misunderstanding Turyshevs comments.  A repeating of the line that Turyshev said GR wasn't used will not be responded to.
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Offline mattyh

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« Reply #58 on: 14/05/2011 00:29:48 »
First of all, hello peeps.  I had a similar thought to yours mike and after a bit of searching, i was directed here.

I have to say, having read through the thread several times i feel that you've been treated unfair.  All your posts made total sense to myself and used terminology that I'm familiar with. The OP however repeatedly misquoted you and often coined his own phase's.

Maybe we're (well, i am) just of a lesser intellect and dint understand the big picture, lol.

Like yourself the maths of this is way over my head, I had a hunch and decided to research it. Don't all theories start off that way? obviously at some point they need backed up with hard facts, but i guess since we cant do that, maybe we should keep quiet.

Afterall someone may do the maths, write a paper on it and win a nobel prize or something.


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Offline yor_on

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« Reply #59 on: 14/05/2011 04:53:49 »
Mattyh, one don't has to like it, but one do need to know the 'mainstream' definition, Einsteins own actually, first. As for needing the math? Oh yes, you will need to learn it, and as you do you also will need to redefine Einstein's definitions to fit this idea of 'variable light'.

Myself I don't find it possible.
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Offline MikeS

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« Reply #60 on: 14/05/2011 08:52:39 »
Mattyh,
My sincere thanks, that's the only bit of encouragement I have received on this site.
Quote from: yor_on

link=topic=38611.msg355773#msg355773 date=1305345229
Mattyh, one don't has to like it, but one do need to know the 'mainstream' definition, Einsteins own actually, first. As for needing the math? Oh yes, you will need to learn it, and as you do you also will need to redefine Einstein's definitions to fit this idea of 'variable light'.

Isn't it amazing how people try to turn things around.  My ideas are to the best of my knowledge completely in keeping with Relativity as expressed in my previous posts.  I assume the above is another missquote like the rest you mention. The same can not be said about about yor_on who while telling me I had got relativity wrong quite obviously did not understand gravitational time dilation himself.  Having said that I note from his latter posts that his attitude towards gravitationa time dilation is now falling more inline.

If you are interested in gravitational time dilation you may be interested in my articles on Time and Gravity in the New Theories section.  They do contain the maths but no replies.  You just can't win.

Thanks again

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Offline MikeS

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« Reply #61 on: 14/05/2011 08:59:34 »
I should have added by way of update.  I have e.mailed Nasa once and Jpl twice in the last seven weeks on the Pioneer anomalies and am still awaiting replies. 

If I were definitely wrong then I would have expected a reply by now.

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Offline imatfaal

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« Reply #62 on: 14/05/2011 10:57:10 »
Mike - please stop asserting in the Physics forum that your ideas are mainstream, they simply are not. 

I have explained here why your points about JPL not using any GR in their calcs are simply wrong.
http://www.thenakedscientists.com/forum/index.php?topic=38611.msg353958#msg353958

I will take the time to have a look at your thread in New Theories - but as you have already posted that
the maths to calculate the effect of GR time dilation on the above probe is beyond then there is no way that you can validly approximate your theories to mainstream views.  The complexities of GR are formidable and beyond all unless they are willing to dedicate time and effort to it.

Lastly please do not criticise another member of the forum or question their knowledge apart from within the context of a debate with that member and addressed to that member.

matthew
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Offline mattyh

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« Reply #63 on: 14/05/2011 15:46:01 »
I'd like to apologise for flaring things up, that was by no means my intention here. (Late night, a few beers, then a boat load of coffee).

On a final note I'd like to say, If everyone had the same views, used the same proven science and no one took that 'leap of faith', would science (hell, even the World) be better off? I don't think so, it needs people who think outside the box to move forward. Diversity is the key, much like in evolution.

Kind regards Matt


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Offline imatfaal

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« Reply #64 on: 14/05/2011 16:07:07 »
Think nothing of it Matt - if we didn't relish a little cut-n-thrust we wouldn't be here! 

I don't think there is a single scientist, amateur or professional, lay or academic, who would disagree with you; but science moves on with new ideas that are challenged, shown to be consistent with evidence, and build upon or overthrow the current thinking.  What science does not do is envisage an idea and insist it must be correct because it 'feels right' or it fits an internal logic; merely providing an alternative heuristic is no good whatsoever if the new underlying theory does not corectly explain and predict experimental results.  Many of the great ideas of science seem to be simple isolated logical plans backed up by easily understood thought experiments - however, they are in fact also founded upon amounts of data, maths, and interconnecting logic.  There will no doubt be another great leap forward in our understanding, which after the fact will seem simple, and which may be pilloried at first; but the vast majority of science is hard work and slow grind.
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Offline yor_on

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« Reply #65 on: 14/05/2011 18:29:44 »
Mike, I believe the way I look at light here as being the way Einstein looked at it too :) And that's just a simple truth.
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Offline MikeS

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« Reply #66 on: 14/05/2011 18:57:29 »
you_on

That's exactly the way I look at it.

If you look back through your posts you could not accept that there are 'pockets' of varying time which are necessary for time to be constant.

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Offline MikeS

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« Reply #67 on: 14/05/2011 19:00:04 »
you_on

That's exactly the way I look at it.

If you look back through your posts you could not accept that there are 'pockets' of varying time which are necessary for time to be constant.

Sorry, should read
If you look back through your posts you could not accept that there are 'pockets' of varying time which are necessary for the speed of light to be constant.

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Offline yor_on

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« Reply #68 on: 16/05/2011 23:52:22 »
Well, that is where we differ. As I said, you can possibly? See it that way. Although it would wreck havoc on the idea of light as a 'constant' and redefine what a constant should be seen as. It would make this universe a lot more complicated though. Going out from the light constant we have a simple way of explaining how 'frames of reference' will produce a time dilation as it comes naturally from that definition. Using your definition it becomes a definition of light not being a constant, more of the room time geometry as a whole being one, with each 'frame of reference' then representing a different island, and as you need to remember, all of them able to be created at a instant, depending on your acceleration. And as I said, neither Einstein nor me have this impression, at least as I understands it.

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Offline MikeS

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« Reply #69 on: 17/05/2011 06:41:53 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

You have previously referred to this as 'pockets of time' and denied that they can exist.  Furthermore, you have said that both you and Einstein are on agreement on this.  You are not.  Pockets (your word) of varying passage of time do exist.  This is in full accord with what Einstein said.

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Offline JP

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« Reply #70 on: 17/05/2011 07:13:32 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."

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Offline yor_on

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« Reply #71 on: 17/05/2011 09:02:20 »
Yep that's true, I keep forgetting to add this 'inertial' definition. What that mean is just that light is defined as moving at 'c' anyway we measure it in a inertial frame as Earth. But the same will hold true for an accelerating frame too. He defined that one in SR 1905. He used this definition to define how two inertial 'frames of reference' could 'tick' at the same rate while still being defined as measuring all light at 'c'. Why i keep forgetting to add that one is that there are two effects of this definition. One is that all 'local time' will be the same, and that one must be true. That is, your own 'time' as measured by you will alway have the same duration and there will be no way for you to lengthen that time, except relative another frame of reference. The other is that 'c' will hold for accelerating frames too. There is no way I know of to measure light as other than propagating at 'c' in a vacuum.

When I think of the definition of 'inertial frames' I automatically connect it to 'time' as described above.
==

But you're not the only one having this idea of a variable time. I've seen the people using a train analogy with 'light clocks'¨ticking finding it to prove that 'time' is variable. That's wrong, room time is a variable, but only as compared between frames. If time was variable, why would there would be a synchronization when the 'twins' meet up? The mere idea that they will find a time dilation builds on their 'local time' being the same, as long as they share the approximate same 'frame of reference', as on Earth. So your (always) local time, combined with lights invariant speed in a vacuum defines the frames you measure.
« Last Edit: 17/05/2011 10:11:04 by yor_on »
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Offline JP

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« Reply #72 on: 17/05/2011 09:08:21 »
What that mean is just that light is defined as moving at 'c' anyway we measure it in a inertial frame as Earth. But the same will hold true for an accelerating frame too.

Actually, I do have a slight mistake in what I said above.  The speed of light is constant globally in inertial reference frames. 

It is constant locally in non-inertial reference frames. 

Geometrically, this amounts to the speed of light being constant if measured over flat regions of space-time.

If you're in curved space-time, you need to look at a very tiny chunk of it which appears to be flat (just like your backyard looks flat compared to the curvature of the earth), so you say it is locally flat--which means that locally the speed of light is constant.

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Offline yor_on

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« Reply #73 on: 17/05/2011 10:17:00 »
Yep :) but don't mess up my beautiful explanation here please.
We can discuss gravity as only able to be defined by 'point particles' too :)

There is no way you ever will measure light in a vacuum other than at 'c'. And all points might be called 'flat' :) But yeah, that definition is worthy of a thread of its own I think JP. Why did Einstein find it necessary to define it this way?
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Offline MikeS

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« Reply #74 on: 21/05/2011 07:07:15 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."

It's not different at all
E=mc2 says exactly that.  For the speed of light in a vacuum to remain a constant then either length or the'passage of time' have to be variable.  As we use the speed of light to define the length of a meter then 'time' itself is the variable.  In which case "the speed of light in a vacuum is a constant because the 'passage of time' is variable", is a perfectly reasonable statement.

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Offline imatfaal

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« Reply #75 on: 21/05/2011 14:44:33 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."

It's not different at all
E=mc2 says exactly that.  For the speed of light in a vacuum to remain a constant then either length or the'passage of time' have to be variable.  As we use the speed of light to define the length of a meter then 'time' itself is the variable.  In which case "the speed of light in a vacuum is a constant because the 'passage of time' is variable", is a perfectly reasonable statement.

Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.  Distance contracts AND time dilates - they do so that in a non-accelerating frame the speed of light will be measured as a constant.

Your continual use of misleading terminology is very confusing and will stop many taking anything you say seriously.  If you mean time dilation then use the term that people know.  If it is an entirely new (or with different equations) then also say so.  By the way the time dilation side of einstein's theory has been tested to amazing exactness - AND it requires a length contraction to maintain speed of light constancy.  If you are maintaining that no distance contraction occurs then you need to explain how light speed constancy remains when the time dilation is the sole effect and we know experimentally that time dilation follows the equations einstein used.
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Offline MikeS

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« Reply #76 on: 23/05/2011 07:26:39 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."

It's not different at all
E=mc2 says exactly that.  For the speed of light in a vacuum to remain a constant then either length or the'passage of time' have to be variable.  As we use the speed of light to define the length of a meter then 'time' itself is the variable.  In which case "the speed of light in a vacuum is a constant because the 'passage of time' is variable", is a perfectly reasonable statement.

(1)Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.  (2)Distance contracts AND time dilates - they do so that in a non-accelerating frame the speed of light will be measured as a constant.

(3)Your continual use of misleading terminology is very confusing and will stop many taking anything you say seriously.  If you mean time dilation then use the term that people know.  If it is an entirely new (or with different equations) then also say so.  By the way the time dilation side of einstein's theory has been tested to amazing exactness - (4)AND it requires a length contraction to maintain speed of light constancy.  If you are maintaining that no distance contraction occurs then you need to explain how light speed constancy remains when the time dilation is the sole effect and we know experimentally that time dilation follows the equations einstein used.


(1) The speed of light (meaning speed of light in vacuum), usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time. 
http://en.wikipedia.org/wiki/Speed_of_light

 It seems to me that distance is precisely defined as a function of the speed of light (and vice-versa).

(2) I thought the speed of light(in a vacuum)was constant in any inertial frame.

(3)Your continual use of misleading terminology is very confusing and will stop many taking anything you say seriously. 
‘Passage of time’  Einstein, sometimes used the word passage.  'Passage of time', I believe is self descriptive and would be understood by everyone.  Time dilation only refers to time slowing down not speeding up so is imprecise as a term to explain time being variable.  The problem is the inadequacies of language, as we have already established dt/dt makes little sense.

(4)AND it requires a length contraction to maintain speed of light constancy.  If you are maintaining that no distance contraction occurs then you need to explain how light speed constancy remains when the time dilation is the sole effect and we know experimentally that time dilation follows the equations einstein used.
As I understand it, distance contraction only applies to objects traveling at relativistic speed.  Gravitational time dilation is not accompanied by an associated length contraction.  Therefore, length contraction is not required to maintain speed of light constancy.

Speed is distance divided by time.  As long as the arbitrary units defining length and time remain the same (299,792,458 metres per second) the speed of light will remain a constant.  However, the ‘length’ of a second and a meter can both change within that constraint.




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Offline imatfaal

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« Reply #77 on: 23/05/2011 10:36:56 »
No - a metre is defined in terms of the speed of light - there is a difference.  we have found that many measurements can be linked - ie they can be independently measured to a high degree of accuracy AND they can be calculated from other measurements taken from completely different experiments.  to make life easy we set constants in one and only one way - and that means that some measurements are done in terms of other things.  velocity is a function of distance - but the speed of light is so central to out physics that when it comes to measurement we use the speed of light to define the standard metre rule.

On your point on contraction - if you say distance contraction doesn't happen you must explain how relative velocity contraction/dolation works, not just find a circumstance in which it doesnt apply.
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Offline JP

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« Reply #78 on: 23/05/2011 10:58:00 »
No - a metre is defined in terms of the speed of light - there is a difference.  we have found that many measurements can be linked - ie they can be independently measured to a high degree of accuracy AND they can be calculated from other measurements taken from completely different experiments.  to make life easy we set constants in one and only one way - and that means that some measurements are done in terms of other things.  velocity is a function of distance - but the speed of light is so central to out physics that when it comes to measurement we use the speed of light to define the standard metre rule.

Yes.  This is an important point.  The meter wasn't always defined in terms of the speed of light.  It was defined in terms of the size of the earth at one point.  The speed of light was experimentally found to be constant under this old definition.  As a result of this experimental evidence, the meter was redefined since the speed of light was apparently a universal constant.

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Offline MikeS

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« Reply #79 on: 24/05/2011 07:55:57 »
quote from imatfaal
Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.


quote from MikeS
 The speed of light (meaning speed of light in vacuum), usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time. 
http://en.wikipedia.org/wiki/Speed_of_light
 It seems to me that distance is precisely defined as a function of the speed of light (and vice-versa).


quote from imatfaal
No - a metre is defined in terms of the speed of light - there is a difference. 

In your first quote above you say that distance isn't a function of the speed of light. 
In your second quote above you say that distance is a function of the speed of light.
They can't both be correct.

quote imatfaal
By the way the time dilation side of einstein's theory has been tested to amazing exactness - AND it requires a length contraction to maintain speed of light constancy.
I was merely pointing out that in general relativity, gravitational time dilation does not require a length contraction.  Therefore, length contraction cannot be a pre-requisite for the speed of light to be constant.  I am not proposing anything new.   


quote from imatfaal
velocity is a function of distance - but the speed of light is so central to out physics that when it comes to measurement we use the speed of light to define the standard metre rule.

Velocity is a function of distance and time.  As we use the speed of light to define the 'length' of the meter and length (distance) is a function of speed then it's a circular argument.  So when I said that "It seems to me that distance is precisely defined as a function of the speed of light (and vice-versa)." was reasonable.  To measure velocity (speed) we have to use distance but distance is defined from speed which means its a circular argument.

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Offline imatfaal

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« Reply #80 on: 24/05/2011 10:29:28 »
Mike you would be better off reading some physics than flogging this dead horse.  That a unit of measurement is defined by reference to a physical constant does not mean that one is a function of the other.  You must learn that the metre and distance are not synonyms.
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Offline MikeS

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« Reply #81 on: 24/05/2011 11:14:25 »
Let me see if I understand this, you say "that distance is a function of the speed of light" but that the meter which is a unit of distance isn't.  Is that correct?

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Offline imatfaal

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« Reply #82 on: 24/05/2011 12:02:43 »
Let me see if I understand this, you say "that distance is a function of the speed of light" but that the meter which is a unit of distance isn't.  Is that correct?

Mike - are you being deliberately obtuse?  Here is what I said:

Quote
Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.
Quote
but the speed of light is so central to out physics that when it comes to measurement we use the speed of light to define the standard metre rule.
Quote
That a unit of measurement is defined by reference to a physical constant does not mean that one is a function of the other.

To take a phrase out of my post and quote it but remove the words "does not mean" and completely reverse the import of my post is completely out of line.  Which of the above quotes could possibly lead you to think that I had said what you have posted?

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Offline MikeS

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« Reply #83 on: 25/05/2011 09:11:04 »
Correct me if I am wrong but I have always maintained that the speed of light in a vacuum is a constant because the 'passage of time' is variable.  That is in full agreement with Einstein.

Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."


It's not different at all
E=mc2 says exactly that.  For the speed of light in a vacuum to remain a constant then either length or the'passage of time' have to be variable.  As we use the speed of light to define the length of a meter then 'time' itself is the variable.  In which case "the speed of light in a vacuum is a constant because the 'passage of time' is variable", is a perfectly reasonable statement.

Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.  Distance contracts AND time dilates - they do so that in a non-accelerating frame the speed of light will be measured as a constant.


Actually, what Einstein would have claimed is that the speed of light is locally constant in an inertial reference frame in vacuum.  Therefore, observers in different reference frames do not agree when they compare lengths and time intervals.

This is quite a bit different from your claims that "the speed of light in a vacuum is a constant because the 'passage of time' is variable."


I really don't see the difference. 
"the speed of light in a vacuum is a constant because the 'passage of time' is variable."
I could have added
"Therefore, observers in different reference frames do not agree when they compare lengths and time intervals."


Let me see if I understand this, you say "that distance is a function of the speed of light" but that the meter which is a unit of distance isn't.  Is that correct?

Mike - are you being deliberately obtuse?  Here is what I said:

Quote
Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.
Quote
but the speed of light is so central to out physics that when it comes to measurement we use the speed of light to define the standard metre rule.
Quote
That a unit of measurement is defined by reference to a physical constant does not mean that one is a function of the other.

To take a phrase out of my post and quote it but remove the words "does not mean" and completely reverse the import of my post is completely out of line.  Which of the above quotes could possibly lead you to think that I had said what you have posted?



Sorry I got it the wrong way around, please accept my apologies.


I have only just realised what I think is leading to the confusion.
Previously I wrote
"It seems to me that distance is precisely defined as a function of the speed of light".
Perhaps i should have said
"It seems to me that 'the meter as a unit of' distance is precisely defined as a function of the speed of light".


quote imatfaal
Mike just because the metre is now set by reference to the speed of light does not mean that distance is a function of the speed of light.  Distance contracts AND time dilates - they do so that in a non-accelerating frame the speed of light will be measured as a constant.


If I am reading this correctly I think you are saying that 'distance' (the concept) is not a function of the speed of light.  If that's the case I agree.

But I still don't see what made you take issue with me when I said
"the speed of light in a vacuum is a constant because the 'passage of time' is variable."
Would it have been acceptable to you if I had added
"the speed of light in a vacuum is a constant because the 'passage of time' 'in any reference frame" is variable."?

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Offline imatfaal

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« Reply #84 on: 25/05/2011 11:52:14 »
Quote
Sorry I got it the wrong way around, please accept my apologies.
No worries - Thanks.

Quote
"It seems to me that 'the meter as a unit of' distance is precisely defined as a function of the speed of light".
Yes - i would say "in terms of" rather than "as a function of" because any function no matter how complex of a constant is pretty boring.  Even the most natural unit of the length - the planck length has the speed of light in its definition - but then so does the planck time, mass, temperature and charge!

on the "passage of time" usage - it is non-standard; this is a highly non-intuitive and recondite area of physics and we cling to standard definitions and usage.   Why use a term that needs explanation when time dilation is easily used; passage of time (for me at least) brings in metaphysical questions. Philosophers since Augustine (and probably before) have pondered the passage and perception of time - it is important to remove experimental physics from abstract philosophy.
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Offline JP

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« Reply #85 on: 25/05/2011 11:56:29 »
And the meter is defined in terms of the speed of light precisely because the speed of light was found to be constant back when the meter was defined in terms of the size of the earth.