How to explain Einstein's Special theory of Relativity.

[John Huang]

Mr. Time is present at both events along with his clock in both IRF's. What other observers are you considering and where are they?

Mr. Time is the object creating events, he does not have to have a clock at all. Observers are in S and S' who record the location and event time in their respective frams.

 

[John Huang]

They are all good, you should spend time on each. At a minimum you need to understand Michelson-Morely, Ives-Stillwell, and Kennedy-Thorndike.

Very good. Let try one by one, please try to answer my question in the link:
https://www.physicsforums.com/showthread.php?p=4197629#post4197629
Thanks.

 

[ghwellsjr]

Mr. Time is the object creating events, he does not have to have a clock at all. Observers are in S and S' who record the location and event time in their respective frams.

Oh, Mr. Time doesn't have a clock. Any particular reason why you called him Mr. Time if he has no concept of time? Can we assume that he has a heart that beats once per second or that he can count out approximate seconds of time interval? Or is it important to you that he just raises his finger at any arbitrary and random time and then curls his finger at any arbitrary and random time later?

Now about these other observers in S and S'--can we assume that at each light-second of spacing from the origin there is another observer who has a clock that has been synchronized to the observer's clock at the origin according to Einstein's convention? Do you want to assume that both sets of observers are present in both IRF's?

 

[Dale]

Very good. Let try one by one, please try to answer my question in the link:
https://www.physicsforums.com/showthread.php?p=4197629#post4197629
Thanks.

You didn't have a question there. But the point remains that SR explains ALL of the experiments listed, not just one or two. If the MM experiment confuses you, then select one of the many others on that page. They are organized topically, so there should be an equivalent one that makes sense to you.

 

[John Huang]

You didn't have a question there. But the point remains that SR explains ALL of the experiments listed, not just one or two. If the MM experiment confuses you, then select one of the many others on that page. They are organized topically, so there should be an equivalent one that makes sense to you.

Sorry, it is not clear in that link. Here is the question. What is the definition of the speed of a beam or a ray of light in the beam?

 

[John Huang]

Oh, Mr. Time doesn't have a clock. Any particular reason why you called him Mr. Time if he has no concept of time? Can we assume that he has a heart that beats once per second or that he can count out approximate seconds of time interval? Or is it important to you that he just raises his finger at any arbitrary and random time and then curls his finger at any arbitrary and random time later?

Mr. Time has concept of time but he does not need to kinow when he raises or curls his finger. That is why there are a lot of possible event points times as of where is A then where is B and the related event time as of when is t1 that Mr. Time is at A and raising his finger then when is t2 that Mr. Time is at B and curling his finger.

I just let A to represnt the location of event 1 (the raising event) and B to represent the location of event 2 (the curling event). I also use t1 and t2 to represent the respective event time measured by observers in S.

The easiest way to measure event times is to ask observer at A to measure t1 for event 1 and the observer at B to measure t2 for event 2.

If we select one obsever at point D in S to measure events then we must adjust the measured event time T1 and T2 to actual time t1=T1-(AD/c) and t2=T2-(BO/c), c is the speed of light.

Now about these other observers in S and S'--can we assume that at each light-second of spacing from the origin there is another observer who has a clock that has been synchronized to the observer's clock at the origin according to Einstein's convention? Do you want to assume that both sets of observers are present in both IRF's?

In the real world we are unable to test Galilean Transformation (GT), because the arranged systems are unable to coexist due to one space allows only one observer, when O' meet O, two observers at origin points will collide. Both of GT and LT are mathematical settings.

Since it is a mathematical setting, we assume that there are stationary observers everywhere in S with synchronized clocks and there are also moving observers (but they are stationary in S') everywhere in the S' with another batch of synchronized clocks.

 

[ghwellsjr]

I'll take that answer to be yes to my last two questions.

Now I want to make sure I got the scenario correct. Mr. Time is stationary at the origin of the S' frame and maps out story 2 as depicted in the first graph in post #103, correct?

And Mr. Time is traveling at some high speed in frame S, starting at the origin of both frames when they coincide and maps out story 1 as depicted in the second graph in post #103, correct?

Now I hope you realize that I used the LT to create the second graph from the first graph, so I presume that you have no problem with either graph, correct?

And we are going to consider that the observers who are stationary in the respective frames are the ones that establish the coordinates of the two events for Mr. Time, correct?

And what's the problem?

 

[Dale]

Sorry, it is not clear in that link. Here is the question. What is the definition of the speed of a beam or a ray of light in the beam?

There are two basic velocities useful for defining the speed of a wave: phase velocity and group velocity. Here is a good page on their definitions and their relation to the propagation of information:
http://www.mathpages.com/home/kmath210/kmath210.htm

 

[Dale]

In the real world we are unable to test Galilean Transformation (GT), because the arranged systems are unable to coexist due to one space allows only one observer, when O' meet O, two observers at origin points will collide.

This is not true. If the Galilean transformation were correct then there would be no time dilation and Doppler shifts would take their pre-relativistic form. So any experiment testing time dilation or Doppler is an experimental test of the Galilean transformation. See the page I posted earlier for many such experiments, all confirming the LT and experimentally falsifying the Galilean transformation.

 

[John Huang]

There are two basic velocities useful for defining the speed of a wave: phase velocity and group velocity. Here is a good page on their definitions and their relation to the propagation of information:
http://www.mathpages.com/home/kmath210/kmath210.htm

That is for a group of photons or a pulse of light. What we need in MMX is for continuous wave, a ray or a group of ray, a beam.

 

[John Huang]

This is not true. If the Galilean transformation were correct then there would be no time dilation and Doppler shifts would take their pre-relativistic form. So any experiment testing time dilation or Doppler is an experimental test of the Galilean transformation. See the page I posted earlier for many such experiments, all confirming the LT and experimentally falsifying the Galilean transformation.

I will talk about Ives-Stilwell Experiment after we finish the MMX issue. One by one.

 

[Vorde]

That is for a group of photons or a pulse of light. What we need in MMX is for continuous wave, a ray or a group of ray, a beam.

What is the difference to you? How do you think you would go about defining the speed of 'a ray of photons' without talking about the speed of the photons themselves?

 

[John Huang]

I'll take that answer to be yes to my last two questions.

Now I want to make sure I got the scenario correct. Mr. Time is stationary at the origin of the S' frame and maps out story 2 as depicted in the first graph in post #103, correct?

And Mr. Time is traveling at some high speed in frame S, starting at the origin of both frames when they coincide and maps out story 1 as depicted in the second graph in post #103, correct?

Now I hope you realize that I used the LT to create the second graph from the first graph, so I presume that you have no problem with either graph, correct?

And we are going to consider that the observers who are stationary in the respective frames are the ones that establish the coordinates of the two events for Mr. Time, correct?

And what's the problem?

The story 2 is maped out by two figures in your #81, the first one is for S and the second one is for S'.

To put the story 1 on figure, the first figure for S will be event 1 (0.866, 1) and event 2 (1.732, 2); the second figure for S' will be event 1 (0, 0.5) and event 2 (0, 1).

The problem is LT supports SR in the story 1 but LT supports anti-SR in the story2 so that logically speaking, if LT is correct then anti-SR and SR should have equal chance to be selected by the nature.

 

[John Huang]

What is the difference to you? How do you think you would go about defining the speed of 'a ray of photons' without talking about the speed of the photons themselves?

You talked about two issues.

My opinion for the first one is, the speed of a ray is different from the speed of a pulse of light. My comment for the second one is, I did not say so and in my definition of the speed of a ray of light do relate to the speed of a photon.

What is your definition for "the speed of a ray of light"?

 

[Vorde]

You talked about two issues.

My opinion for the first one is, the speed of a ray is different from the speed of a pulse of light. My comment for the second one is, I did not say so and in my definition of the speed of a ray of light do relate to the speed of a photon.

What is your definition for "the speed of a ray of light"?

What is a ray of light? A group of photons.

What is the speed of a ray of light? The speed of the constitute photons. (Here is where one might differentiate between phase and group velocity).

What is the speed of the constitute photons? C.

 

[John Huang]

What is a ray of light? A group of photons.

What is the speed of a ray of light? The speed of the constitute photons. (Here is where one might differentiate between phase and group velocity).

What is the speed of the constitute photons? C.

Based on your answer, the speed of a ray of light is c but the speed of a pulse of light could be different. However, I think you will deny your own answer if you think about your answer to your first question ONCE AGAIN.

You mentioned about a very important question, "what is a ray of light?". But your answer MISSED one major factor and one minor factor. First of all, we need one thing besides photons to define a ray of light. The minor one is, to understand MMX clearly we should know a key concept, which was named "first space" by Zhizhong Cai in year 2010.

So, could you modify your answer to your own important question with more detail, like to DEFINE a ray of light? My answer to the speed of a ray is relative to the definition of a ray of light and I need someone to confirm it. Could you help?

 

[Vorde]

First of all, I don't think you understand properly the difference between group velocity and phase velocity, but regardless, for this conversation all we need to consider is phase velocity.

Second, and pardon the language, what the hell is 'first space'? It sounds like baloney to me, so I'm going to ignore it unless you can back that phrase up with some sources.

Third of all, I don't need to define a 'ray of light', I'm taking about photons: which is what light is actually made of. If you want to claim that a 'ray of light' acts differently than photons that's fine, but it doesn't matter because photons are what exist so that's all we need to worry about, and photons travel at c.

 

[ghwellsjr]

The story 2 is maped out by two figures in your #81, the first one is for S and the second one is for S'.

To put the story 1 on figure, the first figure for S will be event 1 (0.866, 1) and event 2 (1.732, 2); the second figure for S' will be event 1 (0, 0.5) and event 2 (0, 1).

The problem is LT supports SR in the story 1 but LT supports anti-SR in the story2 so that logically speaking, if LT is correct then anti-SR and SR should have equal chance to be selected by the nature.

Is the issue that you're concerned about that if you use the LT to get from S' to S using a speed of 0.866c, you cannot use the LT the other way, to get from S to S' using the same speed?

 

[Dale]

That is for a group of photons or a pulse of light. What we need in MMX is for continuous wave, a ray or a group of ray, a beam.

I don't know what would make you think that. Please identify the phrase in that document that led you to that mistaken idea and hopefully I can help clarify your misunderstanding. You can also Google both "phase velocity" and "group velocity" to get a broader understanding if you are still confused.

Furthermore, both group velocity and phase velocity are defined for QM wavefunctions just as well as they are defined for classical waves. So the quantum/classical distinction you are trying to draw is irrelevant wrt wave velocity.

Btw, the MMX used an unmodulated beam of light, so there was no group velocity, only phase velocity. Also, the medium is non-dispersive, which removes a lot of complications. For the purpose of the MMX discussion, the applicable definition of velocity of the continuous beam is the phase velocity.

 

[Dale]

The problem is LT supports [STRIKE]SR [/STRIKE] JHT in the story 1 but LT supports anti-[STRIKE]SR [/STRIKE] JHT in the story2 so that logically speaking, if LT is correct then anti-[STRIKE]SR [/STRIKE] JHT and [STRIKE]SR [/STRIKE] JHT should have equal chance to be selected by the nature.

I have corrected your statement. As discussed over and over and over again, the LT is part of SR, so it always supports SR and never anti-SR. Your assertion to the contrary is flat wrong and has been corrected multiple times already.

If you believe otherwise then please provide a mainstream scientific reference that supports your claim that any prediction of the LT ever violates SR. If you cannot produce such a reference and you repeat this claim then you are engaging in speculation which is against the forum rules.

 

[John Huang]

Is the issue that you're concerned about that if you use the LT to get from S' to S using a speed of 0.866c, you cannot use the LT the other way, to get from S to S' using the same speed?

No. As I understand, we use LT to get from the measurement of S to calculate the expected measurement of S' and the inverse LT for the reverse purpose.

 

[John Huang]

Third of all, I don't need to define a 'ray of light', I'm taking about photons: which is what light is actually made of. If you want to claim that a 'ray of light' acts differently than photons that's fine, but it doesn't matter because photons are what exist so that's all we need to worry about, and photons travel at c.

Yes, it is fine to say light is actually made of photons, but, how do photons make up light?

More precisely, if we define a ray as a thread of light then how do hpotons make up a ray? That is what I mean, we need a definition for a ray, a thread of photons.

In the English version of the 6/30/1905 paper, Einstein used the term {Any "ray of light" moves ...} for his second postulate. If you do not have a definition for the "ray of light" how do you understand the speed of a "ray of light"?

 

[Mentz114]

Yes, it is fine to say light is actually made of photons, but, how do photons make up light?

More precisely, if we define a ray as a thread of light then how do hpotons make up a ray? That is what I mean, we need a definition for a ray, a thread of photons.

In the English version of the 6/30/1905 paper, Einstein used the term {Any "ray of light" moves ...} for his second postulate. If you do not have a definition for the "ray of light" how do you understand the speed of a "ray of light"?

None of this is relevant. It is straightforward to measure the speed of light. See

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

 

[Dale]

In the English version of the 6/30/1905 paper, Einstein used the term {Any "ray of light" moves ...} for his second postulate. If you do not have a definition for the "ray of light" how do you understand the speed of a "ray of light"?

The important thing is that the speed is invariant, not that light happens to travel at that speed. We now know that any massless particle will travel at the invariant speed, and light was simply the first such phenomenon that we encountered.

 

[Vorde]

Yes, it is fine to say light is actually made of photons, but, how do photons make up light?

More precisely, if we define a ray as a thread of light then how do hpotons make up a ray? That is what I mean, we need a definition for a ray, a thread of photons.

In the English version of the 6/30/1905 paper, Einstein used the term {Any "ray of light" moves ...} for his second postulate. If you do not have a definition for the "ray of light" how do you understand the speed of a "ray of light"?

This is pure terminology. And you are talking nonsense. Light is just photons moving at c. If you want to call a group (or thread, if that floats your boat) of photons by another name, that is fine, but it will still move at c.

If you cannot realize this, than it is meaningless to continue this argument as you will get nowhere.

Also DaleSpam just said a really good point, it's the invariance of the speed of the light that matters, not the speed itself.

 

[John Huang]

First of all, I don't think you understand properly the difference between group velocity and phase velocity, but regardless, for this conversation all we need to consider is phase velocity.

When we focus on just a a single line in a beam of light, not a group of different frequencies of rays in a beam of light, then what are you going to name that single line of light? Since the name "ray" is the best one available for a single line in a beam of light I adoppted it for that purpose.

I guess I should say a SINGLE line in a ray of light to make things clear. I will use a new term S-ray for that purpose. Mathematically, a ray is a straight line extending from a point, my S-ray is for a SINGLE line in a ray of light.

It is good to think about a helpful term. My new term "story" for "all events related to an object" did correct my confusing idea of "event period", what I should use is "events period" or even better, "time period between two events". Now I know that in physics, the term "world line" is for the purpose of my adopting of the new term "story". However, the "world line" is for spacetime and I am trying to let the "story" stay in space and time.

Yes, the velocity of an S-ray is defined as its phase velocity in physics. However, that definition is unable to cover the S-ray emitted from a moving (or also spinning, like the source of light in the MMX) source of light. That is why I like to know what is the proper way to define the speed of an S-ray. Do you have any idea?

 

[John Huang]

This is pure terminology. And you are talking nonsense. Light is just photons moving at c. If you want to call a group (or thread, if that floats your boat) of photons by another name, that is fine, but it will still move at c.

If you cannot realize this, than it is meaningless to continue this argument as you will get nowhere.

Also DaleSpam just said a really good point, it's the invariance of the speed of the light that matters, not the speed itself.

I think it is good for physicists to study a SINGLE line in a ray of light, an S-ray, not only a ray includes a group of S-rays. Now, let me try to define the speed of an S-ray. Let me start from the definition of the speed of a ray.

A ray is emitted from a source. A ray can be emitted from the location of the source to all possible directions. A ray always has a starting point but when physicists talking about the speed of a ray they don't even mention about the starting point. Am I correct?

It looks fine (but actually not) when the source of the ray is not spinning. When the source of the ray spins, what will happen to the ray? Ths photons in the ray will go to different directions. How do you define the speed of that ray in that situation?

 

[John Huang]

None of this is relevant. It is straightforward to measure the speed of light. See

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

Thanks. It will not harm if we try to understand how photons organize themselves to make a ray of light. That is what I am trying to do and I hope someone will provide his or her idea about it to help me.

 

[Vorde]

You are inventing a term and then asking us how it would act. It does not make sense to think of light as rays in this situation. The ray theory of light was disproved a long time ago.

You need to understand this. Rays of light is a convenient term to describe light as it moves and reflects/refracts but it is not how light actually works. So if you want to understand how light behaves in order to answer your original questions you need to accept and think about light as individual photons because that is what they are.

When we focus on just a a single line in a beam of light, not a group of different frequencies of rays in a beam of light, then what are you going to name that single line of light? Since the name "ray" is the best one available for a single line in a beam of light I adoppted it for that purpose.

These mathematical entities you are describing (rays) do not have any physical significance here. Light of any form are just photons. Light that is emitted in a way that makes it look like a ray is simply a group of photons emitted in a linear order. Light emitted outward from a circling emitter are just photons being emitted in a spiral pattern. The speed of any of these photons is c.

You could argue that this thing you are calling a ray might travel at a speed different that c. But this thing doesn't have any physical significance, the only things that exist physically are photons and they travel at c.

 

[Mentz114]

Thanks. It will not harm if we try to understand how photons organize themselves to make a ray of light. That is what I am trying to do and I hope someone will provide his or her idea about it to help me.

This is not relevant to SR but you should read Feymann's book "QED - The Strange Theory of Light and Matter "

http://www.amazon.com/dp/0140125051/?tag=pfamazon01-20

 

[Dale]

It is good to think about a helpful term. My new term "story" for "all events related to an object" did correct my confusing idea of "event period", what I should use is "events period" or even better, "time period between two events". Now I know that in physics, the term "world line" is for the purpose of my adopting of the new term "story". However, the "world line" is for spacetime and I am trying to let the "story" stay in space and time.

That is a bad distinction to make as it is self contradictory. Events are already elements of spacetime, so a set of events will also be part of spacetime. Using nonstandard terminology doesn't change that.

Yes, the velocity of an S-ray is defined as its phase velocity in physics. However, that definition is unable to cover the S-ray emitted from a moving (or also spinning, like the source of light in the MMX) source of light. That is why I like to know what is the proper way to define the speed of an S-ray. Do you have any idea?

It doesn't matter if you are talking about the speed of a photon, a classical EM wave (which is an approximation to photons), or a ray (which is an approximation to classical waves), the speed is defined by the group or phase velocity as defined in the page I linked to previously. As also mentioned previously, in the MMX the relevant speed is the phase velocity. Rays, waves, and photons all use the same definition.