Briefly, I agree with your numbers, but not in any absolute sense. The numbers you obtain using your method [on the embankment] would be those you'd obtain standing on ANY moving object [as well] watching the train go past.
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Now, if I were to take the same light travel events and measure them in a different frame, I would measure different travel time intervals and, applying your same calculational procedure, calculate a different relative speed.
For example, suppose I measured those one-way travel times in the frame of the train. In that case, I would find, experimentally, that the light travel times were the same in both directions, and I would therefore calculate that the speed of the ship was zero relative to the ship's reference frame.
At this point, therefore, Motor Daddy, we don't have a disagreement about mathematics (with a couple of caveats I'll mention below). What we disagree about is how the universe actually works. You imagine that you'll always measure two different travel times for any object in motion relative to your hypothetical "absolute zero speed" reference frame. But actual, real-world experiments say different. They show that Einstein's two postulates of relativity do not mandate an "absolute zero speed" reference frame. In fact, they say that the laws of physics apply equally in ALL frames of reference and that there are no preferred frames.
Now, there's no way I can convince you of the truth of Einstein's posulates by arguing about them or showing you the maths, just as there is no way you'll ever convince me of your absolute reference frame by specifying calculation methods or making assertions. The final arbiter of who is right and who is wrong is nature herself. We have to look at what real-world experiments and observations tell us. We need to see what our respective theories predict, then do the experiment, then see who was right and who was wrong.
As a matter of fact, there are literally millions of separate experiments that show that Einstein was right and you are wrong. Many of those experiments use methods that go way beyond your direct measurements of times and distances. There are relativistic effects you probably have never heard of which have been verified as accurate to tens of decimal places. But the theory that has been verified rests on just those same two postulates that apply to basic measurements.
I previously asked you whether you believed in $$E=mc^2$$, for example. If you do, then you either have to believe in Einstein's spacetime (since that is where the equation comes from), or you have to produce some way of deriving the equation using your absolute picture. There's no other option, because the validity of the equation itself has been established experimental beyond all doubt.
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To take one other example at random, your theory cannot calculate observed Doppler shifts of light correctly. Einstein's can. If the police used your theory to calibrate their radar guns, they'd get the wrong answers.
Your numbers don't prove anything about Einstein's theory. All you have done, essentially, is to work in the ground reference frame and then imagine that that particular frame has absolutely zero velocity, without even realising that that's what you're doing.
You don't seem to have any real ability to even imagine how things translate between reference frames. You're firmly anchored to the reference frame of the ground under your feet, and when it comes down to it, you really believe that the ground is (absolutely) not moving.
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Every first-year undergraduate with a week of lectures on Einstein's relativity understands that light travels in space the same distance in the same time. What those first-year students understand that you do not is that this fact is true in any reference frame. Moreover, they understand that the only way that it can be true in all reference frames is if our intuitive ideas of space and time are altered in the way that Einstein derived from his posulates.
What you mean when you make your statement is that you think there is a single preferred reference frame, and light always has the same speed in that one frame. You actually believe that it is impossible to make valid measurements in any other frame, and so it really makes no sense to even try to measure the speed of light in any other frame, let alone the speed of some other object.
You're clearly limited in the extent to which you can visualise different reference frames. Essentially, you always imagine only one frame and you're unable to mentally translate yourself into any different frame. You're always outside the train watching it go past; you don't seem to have the capacity to put yourself inside to see what happens there. And so you imagine that light travel times inside a moving train will always be different in the two directions. In actual fact, if you're inside the train, the light travel times are always the same in both directions. That's an experimental fact, not an imagined one.
Here's another example your theory can't cope with:
Suppose I'm on a train travelling along the track at 0.8c. I fire a missile (or throw a ball or whatever) at 0.5c relative to the train, in the same direction the train is moving relative to the track.
Question: how fast does somebody standing on the track see that ball moving?
Your answer will be 0.5c if you think all speeds are absolute and relative speeds are impossible or make no sense. Or, your answer will be 1.3c, because you believe that the track is an absolute frame and, more importantly, you believe in an absolute time and space that does not really exist. No other answers even begin to occur to you.
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I'm not sure whether you're familiar with the history of Einstein's theory and the questions in physics that led to its development. Have you heard of the Michelson-Morley experiment, which explicitly aimed to determine the speed of the Earth relative to your hypothetical "absolute zero speed" reference frame (at that time known as the "luminiferous aether")? It was found that the experiment always gave a result of zero, no matter what time of day it was performed, in what direction the apparatus was oriented etc. So, was the Michelson-Morley laboratory lucky enough to be the centre of the universe, absolutely stationary at all times? Or could there be some other explanation for the null results?
Why did physicists think there ought to be an "absolute zero speed" frame in the first place? Well, are you familiar with Maxwell's electromagnetic theory? It predicts a constant speed of light, irrespective of reference frame. In other words, the equations of electromagnetism (a) work in all reference frames, and (b) predict the same speed of light in every frame.
All well and good, you say, because the speed of light is a defined constant that never changes, you say. But your theory predicts mathematically that the speed of light, as determined by Maxwell's equations, should not be the same in every frame. You don't know it does that because you're probably unable to transform Maxwell's equations from one frame to another. But I can do it, and I know the answer. Worse still, your absolute-zero frame stuff doesn't even maintain the existence of travelling light waves between frames. It predicts that if you jump on a moving train, you won't see any light at all, let alone be able to measure anything with it, because your theory predicts that travelling light waves cannot exist in any reference frame except the "absolute zero speed" frame - a silly result that can be shown to be false just by you taking a quick stroll around with your eyes open so you can see stuff.
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In summary, Motor Daddy, we have reached an impasse. No argument you can make about how you imagine light behaves can possibly convince me that it behaves in the way you imagine, because I know it doesn't behave like that from experimental results. But worse, nothing I write here can convince you that your imaginings are wrong, either, because they're all you have. I don't think you're equipped to understand much of the physical theory that led to Einstein's relativity. I doubt you have the mathematical background necessary even to understand the basic results or derivations of the theory itself. If you are aware of any of the experimental evidence, probably you have some explanations of how the expermentals are all flawed because all physicists for the past 130 years have been stupid and only you would have done the experiments correctly. But I'm guessing you're probably only aware of one or two experiments anyway, if any.
Some people try to attack Einstein's theory of special relativity by claiming that it is self-inconsistent. You're welcome to try that if you like. So far, as far as I can see you haven't made that particular claim, which is probably the most common one we see from crackpots here. You have claimed that Einstein's theory gives answers that are inconsistent with observation, but the only way you can support those claims is to point to actual experimental results that contradict the theory. Thought experiments in which measurements taken using light on a moving train, wherein the light has different travel times in each direction in the reference frame of the train won't cut the mustard. That kind of thing doesn't happen in reality; it only happens in your imagination.
To conclude, I think we've gone about as far as we can go with this, unless you can show some kind of fatal theoretical or experimental problem with Einstein's relativity, or you can show some experimental evidence for your theory.
