VandD

Why do you need a train at rest as a starting point? You measure a train passing by. You measure with your measuring stick simultaneous events -in your frame- of the front and rear of the train. That's it. You don't need to 'start' with the length of the train at rest. You don't even have to know the length of the train at rest. The 'reality' we all observer/measure is 4D spacetime, not one 3D world of simultaneous events. Since Einstein we know we all live and move in 4D spacetime. There is only one 'reality' and that's all the events of 4D spacetime. A 3D reality is only one of the many sections through 4D spacetime. A few Einstein quotes: << From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space). << Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. >> (Albert Einstein, "Relativity", 1952). <<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245). Karl Popper about his encounter with Einstein: << The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. He agreed that this had been his view, and while discussing it I called him "Parmenides".... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).

A clock does not "have" a ticking rate either. Only a reference frame 'adds' a ticking rate: the rate depends on the relative speed between clock and frame. If speed is zero, then the clock has the fastest ticking rate of all frames. But it's not a 'special frame'.

The rate of clock ticking only makes sense if you introduce a reference frame. A clock ticks at maximum rate if the clock is at rest relative to the reference frame. But that same clock ticks at a slower rate per a frame if there's relative movement between the clock and the ref frame. The ticking rate of a clock at rest relative to a frame has no preferred status. It's not more "real" than any other ticking rate. Hence a clock does "tick at multiple rates". All inertial reference frames are equally valid: they are 3D sections through 4D spacetime and no frame has a preferred status.

Hopeless. You don't want to accept/understand any sloped x'-axis in a Minkowki diagram. Big problems.

This must be a joke! You relativity guys apparently never understood any sloped x' axis in a Minkowski spacetime diagram? I'm speechless. The frame of the train/rocket observer is a sloped x' axis in a Minkowski diagram. Why? Because it connects different events than the x-axis of the embankment observer. Why? Because of relativity of simultaneity (we talk special relativity, or not?). Events that are/happen/exist simultaneously for the train observer are not the same events as the collection of events that happen/exist simultaneousy for the embankment observer. Do I now have to clarify where relativity of simultaneity come from? Analyzing Einstein train thought experiment might help as a shortcut.

I hoped you would understand the front and rear clock I talked about stand respectively for the P clock and Andromeda clock of my spacetime diagram. All you had to do then is add acceleration from enbankment frame (or train frame when train is at rest) to train/rocket frame relative moving in order to to grasp the backwards running of clock P and faster running of Andromeda clock. Unfortunately that was wishful thinking. Sorry about that. I wonder what your position is about the Andromeda clock rate per rocket frame. Would you accept the Andromeda clock runs faster per rocket frame during rocket acceleration? If you don't accept clock P runing backwards per rocket frame, then you won't accept Andromeda clock running faster per rocket frame during rocket acceleration either. This means you don't understand, and/or won't accept frame rotation during acceleration (and deceleration). Agreed?

Clever. But it won't help you. Based on what you see, you know what happened at a spacelike distance. Let's take a simple case: Einstein's train thought experiment, famliliar to all relativity experts, so I don't need to draw a spacetime diagram. The light signal from both light flashes reach the embankment observer at the same moment. But the light flashes don't reach the train observer at the same moment. Newton speaking one would say: for the train observer both flashes occur simultaneously too, but the light signals do not reach him at the same time. But Einstein teached us that for the train passenger (per his frame) both flashes didn 't happen simultaneously. I.o.w. when the train observer passes the embankment observer, the front flash already occured, but the rear flash still has to happen. If the front and rear clock indicate 12:00 when the flashes hit the clocks (which is the case for train observer AND embankment observer, because events itself are absolute), the train observer, per his frame, none of those two events happen (are part of his 3D reality of events happening 'now' ) when he passes the embankment observer. For the train observer the rear clock shows a time less than 12:00, the front clock a time beyond 12:00. No flashes. Train observer and embankment observer consider a different 3D world of simultaneous events, but share one and the same 4D spacetime. Remember some Einstein quotes about 4D existence: << From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space). << Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. >> (Albert Einstein, "Relativity", 1952). <<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245). Karl Popper about his encounter with Einstein: << The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. He agreed that this had been his view, and while discussing it I called him "Parmenides".... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).

I think YOU are in the wrong thread. In Granpa's chart (post#5) - see below- he didn't say anything about seeing the clock running bacwards. YOU critisized him by stating one cannot SEE the clock running backwards. But that's off topic. And from then onwards you continued critisizing his chart, probably -I guess- because you don't understand what his chart says. I showed in my spacetime diagram what Granpa's 'clock running backwards' means.

Stop nitpicking. A frame determines which events an observer considers happening simultaneously. They all have same time coordinate. Didn't you know that? In my spacetime diagram the event clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame. What you think is wrong. In fact you tell me you cannot read spacetime diagrams nor what they stand for. Will be seen to be? I'm not talking about when an event is literally SEEN by an observer. I talk about when an event happens for an observer. You should know the difference, don't you? Once more: I'm not talking about SEEING a clock run backwards. Granpa deals with a clock running backwards per observer's frame. Sure you know the difference. Don't you? Same time coordinate means happening simultaneously. Whatever the time indication on the clock is. Clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame. Both events have same time coordinate per purple frame.

Let's consider rocket on earth, between planet P and Andromeda. Before the launch of the rocket, the clock time in the rocket on earth is synch with Andromeda clock, Earth clock, and planet P clock: 12:00 o'clock. When the rocket accelerates, the rocket frame of simultaneity events rotates counter clockwise. This means Andromeda clock time event beyond 12:00 shows up in rocket frame of simultaneous events. And Planet P clock time event BEFORE 12:00 become part rocket frame of simultaneous events. Per rocket frame clock P runs backward from 12:00 to 11:00 during acceleration. During the voyage the Andomeda clock rate runs slow relative to rocket time rate (hence f.ex. when rocket time is 13:45, Andromeda time is 14:30. When rocket ticked from 12:00 to 13:45, Andromeda clock ticked from 13:00 to 14:30.) When rocket decelerates, the rocket frame of simultaneous events rotates clockwise making the Andromeda clock time run backwards per rocket frame. (f.ex from 14:30 to 14:00)

I found this post #8 of Janus58 explaining it very well: http://www.sciforums.com/threads/can-u-explain-alberts-theory-without-doppler-effect.143505/#post-3255993 Special relativity is about Relativity of Simultaneity which results in time dilation and length contraction. Visual Doppler effect is about an optical effect. SR is not. Relativistic doppler effect takes care of the time dilation and length contraction of SR.

A few Einstein quotes: << From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space). << Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. >> (Albert Einstein, "Relativity", 1952). <<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245). Karl Popper about his encounter with Einstein: << The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. He agreed that this had been his view, and while discussing it I called him "Parmenides".... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).