Rigidity of a light beam

[swansont]

16 hours ago, vanholten said:

I showed you in B the line consisting of  1’s  measuring 1.323c is not the path of light. The light beam is build up from the source.

Then it's meaningless and confusing. I don't know what your diagram is supposed to be showing.

16 hours ago, vanholten said:

Exactly like you move the top of a vertical ruler along a horizontal line and push it upwards to increase the length above the horizontal. You can’t say that the path of the ruler corresponds with a line connecting the top positions, nor that the length of the ruler is stretched. However, that is what time dilation’s formula does.

No, that's not what time dilation's formula does. The light clock formulation looks at the path of a single photon. Any analysis that looks at multiple photons is not valid, as the photons' behavior need not be correlated — they are independent from each other.

[vanholten]

On 31-10-2018 at 11:03 AM, swansont said:

The motion of the light source has no effect after the photon is emitted, so if the the light source changes its motion, it will not affect a photon that has already been emitted.

If you have a light source shining on a target (y direction), and you and that system are in relative motion (x direction), the light will still hit the target. From your reference frame, the laser + target system is moving, and the photon is emitted at an angle that is not perpendicular to its motion.

(light has momentum, BTW)

 

9 hours ago, swansont said:

Then it's meaningless and confusing. I don't know what your diagram is supposed to be showing.

No, that's not what time dilation's formula does. The light clock formulation looks at the path of a single photon. Any analysis that looks at multiple photons is not valid, as the photons' behavior need not be correlated — they are independent from each other.

Thanks for analyzing this so precisely. It might be confusing, but it's not meaningless. The diagram pictures all possibilities of the relation light/ light source we discussed in this topic. I created this diagram to help understand what the problem actually is. In a first attempt I misinterpret diagram B myself and had to insert numbers to identify the path of the individual photons and get a clear picture. 

Option A corresponds with the common explanation. You can choose the path of each single photon displayed on the diagram. This won't alter the fact that emission under the angle of 49,11º geometrically results in the photon moving at an angle of 30º to the horizontal. The photon won't hit the mirror. This is only one of the objections against emission at an angle. More problematic is the fact that this altered angle has to have a physical cause. The adjustment of the reflectors can't be achieved by relative observation.

Option B. This is option is based on a perception similar to your first quote:

"If you have a light source shining on a target (y direction), and you and that system are in relative motion (x direction), the light will still hit the target." 

In option B, indeed the light will hit the target despite of it being in relative horizontal motion. If the photons move along with their light source they produce these straight vertical beams that will fit the clock. This is what I tried to illustrated with the ruler. 

You replied as quoted above: "The light clock formulation looks at the path of a single photon.- Any analysis that looks at multiple photons is not valid, as the photons' behavior need not be correlated — they are independent from each other."

Diagram B gives the possibility to connect the positions of a single photon over a timespan. Equipped with a mirror the experiment would show a single photon zigzagging up and down; an image similar to most popular illustrations of time dilation.

However, there is a major problem to this. Diagram B shows the actual path of the sequence of photons emitted as 1,2,3,4,5 etc. This actual sequence is perpendicular to the horizontal motion of the light source C. The actual velocity of these photons is c. Connecting all positions of photon 1 results in a straight line  49,11º rotated away from the horizontal measuring 1.323C. Connecting all positions of photon 2 results in a straight line paralel to this first line. Doing the same to photon 3 gives a total of three parallel straight lines and so on. Eventually you create a field of paralel straight lines.

The exact shape of this field is a priori imposed by the horizontal distance in which the light source travels at 0.866c compared to the vertical distance of photons traveling at c. Both distances are expressed in the speed of light. In other words: The dimensions and the proportional relations within this field are supervised by the propagation velocity of light in vacuum.

Suppose SR claims that this field produces a path of photons that deviates from the speed of light, since the length is 1.323. To correct this path and to match it with the speed of light, time dilation needs to be applied. Then the following would happen. If you correct any proportional relation within this field from which all dimensions are imposed by photons traveling at the speed of light, it is inevitable that you retrospectively correct the initial velocity of all these photons and thus the propagation velocity of light in vacuum. Time dilation in B would be like adjusting a diagonal of a square by giving it the length of one side. Because it's obvious light coming from C will never hit the clock's reflector, I think we ran out of possibilities.

 

 

 

 

 

 

Edited November 3, 2018 by vanholten

[Ghideon]

On 2018-11-03 at 10:19 PM, vanholten said:

If the photons move along with their light source

I've tried to read and understand the things addressed in this thread. To contribute I have to ask about movement* in this context; does moving light sources perform some kind of absolute** movement? By what mechanism do you distinguish a moving light source form a stationary one? The statement above seems to make sense only if a light source can move relative to some "absolute rest".

*) inertial motion; motion at uniform speed in a straight line, no acceleration.
**) I think Newton introduced the concept. Einsteins theories don't contain absolute movement.

 

(I've had limited time to respond for a couple of days and try to catch up, sorry if these points have been addressed already.)

[Strange]

2 hours ago, Ghideon said:

**) I think Newton introduced the concept

It goes back to Galileo. He came up with the thought experiment of being in a boat on a perfectly smooth sea with no land visible (he had to use the technology of his day!). If you saw another ship, you would not be able to tell if you were moving and the other ship was stationary or vice versa.

(Newton was born the same year that Galileo died. Coincidence?)

[Ghideon]

21 hours ago, Strange said:

It goes back to Galileo

Thanks for noting that what I stated was unclear. I'll try to clarify: 
Newton introduced absolute space (and time) and discussed absolute velocity. 
Anyway, In the context of this topic and the diagrams posted, I got interested and found https://plato.stanford.edu/entries/spacetime-theories/#4.2.1*. I haven't read all, but chapter 4 "Newton" and, more specific, chapter 4.2.1 "Absolute Space vs. Galilean Relativity" compares Galileo's, Newton's (and other's) views. 

 

*) I haven't searched for a second source yet. I can't make statements about the reliability of the source.

Edited November 6, 2018 by Ghideon
grammar

[Strange]

4 minutes ago, Ghideon said:

Newton introduced absolute space (and time) and discussed absolute velocity. 
Anyway, In the context of this topic and the diagrams posted, I got interested and found https://plato.stanford.edu/entries/spacetime-theories/#4.2.1*. I haven't read all but chapter 4 "Newton" and, more specific, chapter 4.2.1 "Absolute Space vs. Galilean Relativity" compares Galileo's, Newton's (and other's) views. 

Thanks for that. I wasn’t aware of that aspect of Newton’s physics. Interesting that he proposed an absolute velocity but also says it can never be measured!

That site is, judging from the times I have looked at it, appears to be pretty sound. 

[tinkerer]

What might be said here regarding some differences which might exist, if any do, regarding our "light beam" in the discussion being limited to one, and one only, frequency or wavelength, unlike the zillions present in visible light? Add to that the requirement that the waves be in phase with one another, and coherent.

Any differences at all? I'm stumped!   imp

[swansont]

8 hours ago, tinkerer said:

What might be said here regarding some differences which might exist, if any do, regarding our "light beam" in the discussion being limited to one, and one only, frequency or wavelength, unlike the zillions present in visible light? Add to that the requirement that the waves be in phase with one another, and coherent.

Any differences at all? I'm stumped!   imp

The coherence isn't a factor in the discussion, nor is the degree that it is monochromatic. The details of the light would all transform so even as the wavelength/frequency changed the phase relationships would not, since all the waves would be affected equally.