A Purely Hypothetical Question regarding Special Relativity Theory.

Geistkiesel, and others,
Could you please give an answer to the following:

Thanks.

 

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Is not the invariance in the measurement of c within a given unaccelerated frame fundamental? Is it not a direct consequence of Einstein's equivalence principle? Does this not state that you cannot determine your state of motion by performing any experiment within your isolated frame?

 

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I will try. If you take the moving case and have the L and R clocks be mirrors the photons would reflect back to the observer at th eoriginal midpoint of the frame simultaneously. There will be a slight time difference in the moving and stationary cases however. The moving opbserver seeing the simultaneou arival; of the emitted photons might conclude he is at rest.

One explanation is that the "same results" expected is an imposed theoretical condition. Under the limits of the experiment here, obviosly the "same result" assumption appears nt to work, which is the natural reult expected from my pespective. In case 1 the frames are stationary wrt the embankment. In case 2 the frames are moving. One would expect a different measured result using the same laws of physics in both cases, especially of the motion is uniform. In case 2 he energy f he frame wrt the stationary case is greater. Using the C + v and c - v terms is a direct violation of the tenet iof SRT that holds all measurements of the speed of light will result in a measurment of c. This is of vcoursse, obviously correct when we all agree on the constancy of he speed f light. This dioes not, however, negate the use of relative velocity includong light in terms of c + v and c - v.

No one is asserting that light or any massive object is moving faster than the spoeed of light. C + v means only a counted measure of the closing speed of a beam of light and a massive object.

In short what you have been told and understood, like the rest of us at one time or another, seems to be erroneous. I suggest you walk through the experiment with L and R as mirrors and use the left moving photon as a measure of the distances light has traveled (without regard to observers or clocks) assuimg only the constancy of the speed of light. Detect where the "extra time" comes from in the moving case. See why the photons do not reflect at the same time and why they do combine simultaneously at the physical midpoint of the inertial frame. You can do this without any higher maths other than addition and substraction. To start: the left photon moves a distance ct before reaching L (which is moving toward l). The r photons moves the same distance to the right, but R has also moved right.

Where is l after it has moved ct + ct? How far away from the midpoint is l then? How far away from R is r after initially moving ct to the right?

Geistkiesel

 

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Geistkiesel,

I see and understand what you are saying, however, I cling to the principles of Einsteinian relativity. I agree that the intuitive result seems obvious, but I'm not sure it is. I'm working on it.

 

Check Yes for the stationary case.

Check No for the moving case.

Remember the clocks are synchronized on your space ship. Remember also that the motion of light is independent of the motion of the source of the light. Also, remember you are privy only to the printed arrival time of the photons after the fact that were emitted simultaneously from the midpoint. Even if the frame is contracting and even if there is time dilation in the case 2, the clocks will still record a time difference of photon arrivals for the l and r moving photons.

This is the only point I intended to demonstrate with this thread.

Geistkiesel

 

If this is what the invarinace principle m,eans then so be it. The question is not the invarinace principle per se, it is the correctness and accuracy of the principle. If one were to retsrict himself/herself to the invarinace principle and walk away from the thread without a physical reasoning then we are left with what? Blind faith acceptance in principles is the answer, while we ignore the physics of the situation. Who will be the first to assert the eternal truth of any physical principle?

Superlunimal,
Apply the invarinace principle here and analyze this with the experimental results? What must have occured that would manifestly have the two clocks printout the same time of flight of the two photons in the moving case? Does not motion affect both equivalently? Aren't the clocks located such that one cannot change its ticking rate without the other also changing in the same degree? If these questions aren't anwered in the positive must not one then explain the invariance principle in terms of mystery and voodoo? The observers on spaceships aren't mental numb robots, they are trained physicists and engineers who know very well the results of experiments on stationary and moving frames re the speed of light.

As an after thought, it appears to me that the invariance principle as stated by yourself is a correct statement of the principle, which only restricts the measurnment of the motion. The principle does not deny the fact of motionj itself, only the measurment. This however, as we have seen by the experiment here points to an apparent flaw in the principle as understood, or so I humbly assert.

Geistkiesel

 

What is so puzzling or slicky about a printout of a time from a clock on a moving platform? Observations aren't voodo they are, in this experiment, simply looking at numbers printed on two pieces of paper.

Xgen, To begin, focus only on the arrival times opf the photons at L and R. Are the arrival times the same for the two cases discussed?

If the clocks are synchronized the light, if reflected back to the midpoint observer, will arrive their simultaneously, but if you read the printout of the arrival times at L and R the left moving photon arrives at L before the right moving photon arrives at R, which is unambiguous physical evidence that the frame is moving to the right.

How can you explain this differenltly?

Geistkiesel

 

Go for it, just keep Ms. Objectivity forever vigilant in your explorations. Thank you for the intelligent, cogent and professionally submitted comments and questions.

Geistkiesel

 

Geistkiesel,

This seems correct at first inspection. My issue is that I have a long held belief in the Einsteinian view of things, and have had my physical intuition about this sort of experiment turned around and explained nicely in terms of relativity. I admit that I'm having difficulty with this one. Getting "unambiguous physical evidence that the frame is moving to the right" upsets my apple cart.

 

Superluminal,

1. To whom was addressed post with “YES or NO”?
If to me (or to me also) my answers are the following:
If L_M_R device is rested in respect to you – in both cases “YES”
If in any case L_M_R device is moving in regard to you – in that case answer is “NO”.
(BTW, look how many words in your post, that were used, are absolutely useless for the right answer: all what matters is your and device relative velocity in respect to each other)

2.

The Principle of Relativity summarizes our knowledge in simple statement that the events are the same, not the descriptive characteristics of events. Simultaneity of two events is not an event! “Light reached receptor” – is an event. “This two events happened simultaneously” – is not an event. Same as “this line has length L” is not an event, but “my length-meter read a length L” is an event! I hope you understand what I am saying here – it is very, very important to apprehend SRT!
And now about c = constant. Here you are mixing two very important issue too. The velocity of any body is purely relative notion and strongly depends on the dynamical state of observers in respect each other. But speed of light is not! Speed of light (in vacuum!) is absolute World-constant and is absolutely independent on motion of observers and/or of source of light! This fact of Nature is a fundamental base of understanding of the natural features of Space and Time. Why it happens so and what is responsible for that – those are the gnoseological questions and we can know the answers or not (yet). But it does not change the fact that it is the fact of Nature.

3.

I can not help you because you did not concretize relative motion of L_M_R device and observer. If you will do it my absolute answer, which always is the same “No, nobody will measure different speed of light for any leg”, could be supported by calculations why it is true and your assumption is wrong, i.e. that there is no problem, at all…

geistkiesel

1.

If he is a smart guy and has learn the classic Physics – never!
2.

Why should he connect such a conclusion … with arriving times of two photons simultaneously emitted in some another reference frame?

No how! There is no way of logic to such a stupid conclusion!
All what you written below this your question (in the same post) is BS. The same concerns your next post, sorry…

3.

When I read your anti-SRT posts – any day is sad in the same measure – you again did not learn anything!…

P.S. This my respons concerns only posts on page 1 of this thread. The page 2 I will comment later...

 

This is interesting Yuiry. I agree with every thing you said and everything you said confirms my belief that SRT is the correct description of the universe. We are definitely having a difficult time agreeing that we agree.

I said:

You said:

I will reword my statement:

If I (the guy on the ship, moving with the apparatus) found that the two clocks read differently in the spaceship, then I would calculate a different "speed of light" for each photon, given that I measure a 1m length for each leg of the apparatus. This would be in violation of everything I understand about SR. In the ship, nothing appears odd to me, therefore I will NOT see different times on my clocks.

Better?

 

About 1/3 down the page. (Simultenaeity)

http://instruct1.cit.cornell.edu/courses/astro101/lec21.htm

 

Superluminal, just a question that came to mind: Other than clinging to the Einsteinian principles as you sway, can you offer yourself any physical reaon to ovecome what you define as obvious? I understand you to mean you understand my input on this matter, which is trivially simple to see..

Geistkiesel

 

Useless to you pehaps as your res[ponse will always be the SRT answer, which has yet been proved to me.

Yuri, take a real close look at the initial post of this thread. The question was simply what the L and R clocks would printout in the case where the frame was moving wrt the embankment, not what a stationary or moving observer would "observe". In any case the observers are not privy to any information other than what canb be observed. Here only the clock times on he moving platform are relevant. Even if there were frame contraction adn time dilation he fact remains that L would meassure an arrival time before the R clock measures a photon. The observer, if you will, strolls to L, pushes a button and gets the time of arrival of the left moving photon. Then the observer strolls to the R clock, pushes another button and reads the time of arrival of the right moving photon.

In the case of the frame at rest with respect to the embankment the tme of arrival of he photons at L and R are the same. We next put the frame in motion to the right and repeat the experiment: photons are emitted simultaneously from an emitter attached to the midpoint of the moving frame (this is the sanme emitter used previously). The clocks at L and R will printout different times of arrival of the photons.

Certainly Yuri you can have no problem with this simple physical sitution.

Geistkiesel

You are correct here. No one can calculate or measure diffeent speeds of slight for the diffeent legs. What we are measuring is the arrival time of he left two photons, only.

geistkiesel
Quote=Yuri]
1.
If he is a smart guy and has learn the classic Physics – never!
2.
Why should he connect such a conclusion … with arriving times of two photons simultaneously emitted in some another reference frame?
[/quote]

Yuri, the photons were emitted in the same physical frame from the same device. In the first case the frame was at rest wrt the embankment, in the second case the frame was moving wrt the embankment. It would have made no difference anyway what frame the photons were emitted, the results are the same.

What stupiid conclusion specifically are ypu referring to Yuri.

The "sad" statement was a joke Yuri, simply a joke.

Do the two photons arrive at the L and R clocks at the same instant in the moving frame as in the case where the frame is at rest wrt the embankment?
Geistkiesel

 

Yes.

 

No.
Exact quantitative answer I already gave.
Anyone who does not understand this answer never will understand SRT. Period.

 

Suprluminal,
You have the true grasp of the problem. Your use of the invariance principle has superceded any attempt to analyze the physics of he moving photons. Bear with me. Likewise you have gone outside the limits of the hypothetical problem.

Your use of invaiance here neglected the option that the frame (at least viewed from the embankment, which the moving observer must be aware of) was moving and that different times of arrival of the photons was due to the frame motion. Do you see what gets neglected here using SRT? Anwser: Physical data.

That you conclude differently than I is of no consequence. Think of the physical condition together with your understanding of SRT. You need not integrate the thoughts simulabneously when constructing a hypothetical situation. Put all the rlevant ideas together in a rational form that are necessary as determiend by your own comfort zone.

Beginning with the photons only, and forgetting about observers for this brief instant we see that

• each photon is emitted at a unique point in space.
• Each photon moves independently of the frame, moving or otherwise.
• In whatever time base one uses, each photon will move the same distance in that time span, relative to the point in space from which they emitted..
• neither photon knows that there are L and R clocks ahead.
• in the 'frame moving to the right case', the L clock is closing (colliding), with the left moving photon while,
• the right moving photon is chasing the R clock.
• When the left moving photon strikes L after travelling ct, the right moving photon has also travelled ct, in the opposite direction.
• when the L clock records the left moving photon arrival the right moving photon has not yet reached R.
• at this point the right moving photon is a distance 2vt from R.

The clocks merely 'stamp' out the current moving frame time when the photons arrive. The data is then open for scrutiny, perusal. What do the topics of "observer at rest" or "moving observer" have to do with the results?
What t do we use? Answer: Any convenient time. The SR theorists use SRT time, the non-SRTists use embankment time. These are of no consequence as the different arrival times is the only important parameter here.

What does the "invarinace principle" have to do with the results?

Even Yuri used the terms, C + V and C - V in an earlier post to this thread. Is not this use of velocity addition assume a violation of SRT where the relative motion of the frame and light is always and axiomatically supposed to be C?

Geistkiesel

 

superluminal,

AFTER SUCH REWORD OF YOUR INITIAL STATEMENT you are talking about Case v=0. The unswer is trivial: clocks rested in regard to you and point M will read the same times. And nothing will be "in violation of everything I understand about SR."
But we are talking about comparison of cases 1. and 2., remamber?

 

Note to the reader: I am takinhg Yuri's statement somewhat out of context here and focus only on these worsds.

Yuri, This is not a discussion of simultaneity or events as described by yourself above. When I say the light/photons were emitted simultaneously from a point source at the midpoint of the moving frame this is not a staenment discussing "simultaneity of events." When I day the photons were recorded at different times on themoving frame, I make no simultabneoty assertion. It is just a physical fact: The left moving phoptn was detected, then later the right moving photon was detected. The lengths of both legs are identical throughout from symmetry considerations an the time of flight for equal distances is identical.

A. The instant L records a photon arrival is an event.
B. The instant R records a photon arrival is an event.

A occured before B as determined by moving frame clocks.
Get in focus.
Geistkiesel

 

There is analysis of your post.
1. When you say the one beam of light (or a photon) was emitted left and another one beam of ligt (or a photon) was emitted from a point source at the midpoint of the (moving or rested - it does not matter) reference frame THIS IS
a. discussion about two events
b. discussion about two events that happened simultaneously
do you like it or not;

2. When you say the one beam of light (or a photon) was arrived on the end of the left leg, and another one beam of ligt (or a photon) was arrived on the end of the right leg THIS IS
a. discussion about two events
b. discussion about simultaneouty or none-simultaneoty of two events
do you like it or not.

For your general information; SRT is only about events, nothing else!, do you like it or not...

So, get in focus.