01-31-06, 04:34 PM #901Originally Posted by MacM
Originally Posted by Physics Monkey
However, in the embankment frame, the color filter at the rear of the train is receiving blueshifted light. There is no difference in the way the atoms in this filter are time-dilated and length contracted compared with the atoms in the filter at the front of the train. Therefore, I do not understand why the blueshifted light would pass through the filter at the rear of the train.
If the time dilation and length contraction cause the bypass frequency of one filter to become lower, why would these same effects cause the bypass frequency of the other filter to become higher? The only other thing that I can conceive of which applies to the rear of the train in a different way than it applies to the front of the train is the loss-of-simultanaety (in the embankment frame, clocks are not synchronized properly across the length of the train). However, I do not see how this could be the solution for the two filters passing different frequencies of light.
Up until now, MacM has not made a very compelling argument for the "different photon" theory, but he just might have scored some bonus points here. What would the SR explanation be for this "relativistic, dopper-related, filter-frequency-shift" phenomenon?
Last edited by Neddy Bate; 01-31-06 at 07:47 PM.
01-31-06, 04:50 PM #902
Originally Posted by Raphael
But I do think that the historical context is important here. The invariance of c was established experimentally long before it became the definition of the meter. In other words, the constancy of c was validated experimentally and the value of c was measured progressively more accurately to the point that the single biggest source of error was the error of determining the length of the metal bar that was then used as the standard. The '83 definition is basically a recognition that even if c is not exactly constant it is at least more constant that the length of a metal bar.
01-31-06, 06:07 PM #903
Originally Posted by DaleSpam
But I do think that the historical context is important here. The invariance of c was established experimentally long before it became the definition of the meter. In other words, the constancy of c was validated experimentally and the value of c was measured progressively more accurately to the point that the single biggest source of error was the error of determining the length of the metal bar that was then used as the standard.
Historically, the 1983 definition replaced the 1960 definition which used a wavelength of krypton-86 radiation. The 1960 definition replaced the 1889 platinum/iridium bar which had replaced a previous bar which was short by .2 millimeters.
Both the 1983 definition and the 1960 definition are only as accurate as measuring device used to take the measurement of distance involved. Which still involves that same metal bar for which you seem to have some distain.
All of which is to say that there was no need to create the existance of circular definitions, as we were already away from the metal bar and at the same time forever tied to the accuracy of the metal bar.
The '83 definition is basically a recognition that even if c is not exactly constant it is at least more constant that the length of a metal bar.
Last edited by Raphael; 01-31-06 at 06:17 PM.
01-31-06, 06:25 PM #904
Originally Posted by Raphael
I still think it makes sense though. If you can measure x more accurately and repeatably than y then it is silly to define x in terms of y.
01-31-06, 06:35 PM #905
I don't think that the definition of the metre implies frame invariance on its own.
If it were possible to measure the length between marks on a bar more accurately than distance travelled by light in a given time, then I have no doubt that we would still use it as a standard, frame invariant or not.
The point of a standard is to make measurements meaningful and communicable.
If I say "the thing is ten metres long, as precisely as I can determine", how precisely do you know the length of the thing?
Without a standard, I'd have to make up my own... I could make two marks on a bar and say "The thing is the same length as the distance between these marks."
Or I could say "The thing is as far as I can walk in ten steps."
And so on.
01-31-06, 07:03 PM #906Originally Posted by Neddy Bate
Perhaps both of the color filters which are in relative motion to the embankment would allow a wider range of frequencies of light to pass through. The explanation might be something along these lines... "Length contraction of the filter causes it to allow shorter wavelengths to pass through, while time dilation of the filter causes it to allow longer wavelengths to pass through. Both of these effects together cause the by-pass frequency range to be widened just enough that the redshifted light passes through the foreward filter, and the blueshifted light passes through the rearward filter."
Any chance this is actually the correct explanation? If so,
01-31-06, 07:05 PM #907Originally Posted by DaleSpam
You may be able to convince yourself that I have repeatedly ignored the issue, but the evidence is right here on this forum. Of course, I realize that you are about as big on evidence as you are on math.
That was someone else. I just showed that your idea was incompatible with an invariant c.
In any case, your one example with a 100 cm line, etc. hardly represents a mathematical framework.
You want to switch to different measurement standards between frames and pretend they are the same. NONSENSE. Go back to kindergarten. 'd' does not change. The only change supportable by conventional physics is a frame dependant velocity and invariant 'd'.
Excellent. This is the most positive step you have taken yet. Now you just need to go from your postulate to any of your conclusions. By the way, a "hence" clause doesn't belong in a postulate since it indicates a conclusion. (Plus this one really proves me correct when I claimed your favorite proof is "Assume A; therefore A.")
01-31-06, 07:42 PM #908Originally Posted by Raphael
I just think that there are physical effects that directly depend upon speed and thus by using them, one need not calculate anything, but one directly measures speed by observing them, no calculations need. - Just calibrate the measurement system that has a response (hopefully reasonally linear in most cases, but not all if very large speed ranges are to directly measured.)
I suggest Doppler shifts and the type of speedometer we have been discussing and certainly my optical mouse speedometer can and do directly measure speed - none work from the definition of measured distance covered in measured time lapse. If they did make these two direct measurement and then calculate the speed, of course I would agree with you that speed is in that case, a derived, indirect measurenment. Your original post claimed that it can not be measured directly. I still think that false, but will not argue the point more as you are becoming a moving target, supressing your original false claim which began this debate.
Let me try one last time, with new instrument - a thin metal strip sticking into a long oil bath with a scale adjacent to its sharp edge of the strip. I assume you claim the deflection of the finger strip is directly measuring viscous force even though it is calibrated in m/sec. Why if the m/sec scale replaced is with one calibrated in pounds (the "lbs scale") does this instrument suddenly become become a direct measurement instrument (of force) yet it was not a direct measurement instrument for speed? Again your position appears a little silly to me.
Last edited by Billy T; 01-31-06 at 07:57 PM.
01-31-06, 08:15 PM #909Originally Posted by Neddy Bate
MacM is trying to imply that different energy photons move at different speeds but when many post ago some one noted that the wind can change the speed of light (or difference in atmospheric density) etc. I agreed and said that the light travels inside evacuated tube and the end cap seals of this tube are the photon cells triggers - Do I really need to go thru these details again --put the dam train on the moon or some planet without an atmospere. This is a thought experiment - that means you think and focus on the essentials, not the details of how.
I will belive MacM's different colors (or energy) photons travel at different speed when suppernovas are initially one color and for a few weeks continuously change to a different color, due the MacM's differ energy photons travel differently!
Last edited by Billy T; 01-31-06 at 08:22 PM.
01-31-06, 08:42 PM #910Originally Posted by Raphael
I had essentially nothing to do with this, so know little of the details. Last year the Earth disagreed so badly with the well defined second that a whole second was stuck in (or removed) to 2005. (Probably "stuck in" as Earth's spin is slowing down as moon goes away.)
Summary (still true I think): SOL and second are defined.
The meter is a derived quantity, which agrees with SOL being number that Raphael gave (assuming he has that correct.) and the Naval Observatory's second, a weighted average of about 10 atomic clocks.
Last edited by Billy T; 01-31-06 at 08:55 PM.
01-31-06, 08:43 PM #911
Originally Posted by MacM
Originally Posted by MacM
Originally Posted by MacM
Originally Posted by MacM
That said, I really think that you have made significant progress by finally getting a postulate. Now, all you have to do is prove something (anything) based on that postulate. I think that you will find that the MacM prime postulate doesn't lead you very far by itself. It certainly is insufficient to derive the MacM transform. You still have a long way to go to challenge relativity, but keep trying.
01-31-06, 08:50 PM #912
I wasn't moving away from my original claim. You interpretted the cycle of rotation into a time dependant value. I mearly needed a ratio to convert that value to a value that directly corresponds to the appropriate distance value, the circumference of the tire. From these two values I can calculate the value for velocity, as both time and a distance can be used in the calculation. There is no suppression of an original claim.
Since you wish to be a stickler for original claims, my original claim did not say that velocity must be calculated from the definition of measured distance covered in measured time lapse.
My original question:
Why would velocity be non-calculated when it is impossible to obtain a value for velocity without calculating it from other measured values?
Which I changed for the sake of clarity to:
Why would velocity be non-calculated when it is impossible to obtain a value for velocity without interpreting it from other measured values?
Again I think use of the word calculate is a stumbling block, which as I stated in a previous post tends to bring to mind the use of active math.
Say I need to multiply two numbers. A constant, say 2, and a given number from 1 to 10. Using a slide rule to perform the calculation, I place the 1 over the two and find the variable number on the 1's side and the answer is even with it on the 2's side. Was this answer calculated? I suggest that the tool did the work, but it was still a calculation.
Are we debating semantics, or are we debating that calculating a value by the use of known values and the collected data is the same as/different than directly measuring a value?
Do you really think it makes sense to define x in terms of y which is defined in terms of x? Does it also make sense to take a postulate and make it an absolute?
I'm sorry. The first offends my logical mind, while the second requires faith that I reserve for theological issues.
01-31-06, 09:00 PM #913
Originally Posted by Billy T
The speed of light is a value given in meters per second.
The meter is defined by the speed of light.
It is impossible to measure the SOL without first knowing the value of the meter. By definition, it is impossible to know the value of the meter, without first knowing the SOL.
01-31-06, 09:01 PM #914
Are we discussing whether velocity or distance-time are more fundamental properties?
I don't think there's a meaningful difference, really... I don't know if methods of measurement are awfully relevant, either.
And like I said before, the postulate of frame invariance of light speed is not really relevant to its use as a standard... all that's required is that it doesn't vary measurably in the scope in which we use it.
There's really nothing new about using speed as the basis of a distance standard. Consider - My work place is a 15 minute walk from my home.
As long as I walk at roughly the same speed, that's a perfectly usable distance measurement, right?
01-31-06, 09:07 PM #915
There is actually no contradiction because you've missed another asymmetry between the front and back filters. The back filter is coming towards the light pulse and the front filter is running away from the light pulse. So there is the source asymmetry you've mentioned, but there is also this detector asymmetry. And as I said, this is one of the keys to laser cooling: the lasers are adjusted so that atoms coming toward the laser (i.e. trying to escape the trap) are resonant and interact strongly with the laser where as atoms moving away from the laser interact weakly and feel very little force.
Trust me and don't listen to MacM! If there is an explosion in one frame, there is going to be an explosion in the other.
01-31-06, 09:08 PM #916The speed of light is a value given in meters per second.
It can be given in any number of ways, not limited to d/t.
Eg, a ratio of some other known speed, which might be known directly, or might be determined from momentum or energy, for example.
Or, c = 1/√(ε<sub>0</sub>μ<sub>0</sub>)
Fundamentally, the question of its use as a standard comes down to whether you can use the speed of light to determine an unknown distance, in agreement with other standards of length.
01-31-06, 09:22 PM #917Originally Posted by Raphael
PS Nice to know I am not the only one left who knows what a slide rule is and that it is a stick (or usually two) with with marking spaced by logrithms so added stick lengths is a way to multiply. Did you know that the very first were many sticks (called "Naper's bones"*) and you did litteraly stick them end to end? I have never seen a set of Naper's bones, but assume they were only good for multiplying integers.
* I think they were made of ivory. You can use only the slip stick part and mark on paper lenght 3, then to end mark of that, mark 7 more, then to end mark of that, mark 5 etc. and then measure the distance (with the slip stick of course) of the total length you have layed out and have the product, 3x7x5 = 105. I have found this is a good way to have students really understand why their rule works, but no one cares any more.
Last edited by Billy T; 01-31-06 at 10:00 PM.
01-31-06, 09:24 PM #918
I think the only time I've ever seen a slide rule is when learning logarithms in school.
Nearly 20 years ago...
01-31-06, 09:25 PM #919
Originally Posted by Raphael
01-31-06, 09:36 PM #920Originally Posted by Raphael
I will not argue, but if you know what a Fabry-Perot interferometer is, then start with the plates in contact (in a vacuum usuing your cesium source) and separate them, slowly counting the fringe cycles until you have 9,192,631,770 of them (actually I think there may be a half cycle more or less as the phase shift with internal and external reflections differ by pi as I recall)
I think the distance between the plates is now half the distance light travels in a second and or a known number of meters. What do you think?