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JulianM

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  1. Yes, I agree. I was really just asking Super Polymath to elaborate on what he is trying to say.
  2. I don't disagree with this statement, and math is only useful when based on correct assumptions, but it is necessary to go beyond "more likely". This is off The original topic, but if you have something more than "it could be either" then I am happy to listen.
  3. I get the impression from this that because the string is pinned to the axle it is stopping when all the string is wound off and tight. Is that what is happening?
  4. Yes, I understand. What I am trying to visualize is, if we examine events in a space-time diagram then we should presumably relate each cause and effect in it's proper frame of reference. For example, in the train experiment - - the original flash and the reflection can both be considered in the train's frame of reference - experiencing the reflection (illumination) of the rear of the train and the stationary observer should be considered in the frame of reference of the stationary observer and he experiences it at speed = c In a simple space-time diagram for this we would typically draw
  5. Bangstrom, Thank you for allowing me to follow this line of reasoning. In my consideration of this I next populate the train with a large number of passengers, or Windows works too, and find that each one of them is a little closer than expected in the segment coming towards me, and the opposite in the segment moving away. This makes a kind of analogy to red and blue shift doppler effects if we think of a wave form drawn over their heads. The next step in thinking about this is that I can be fooled into thinking that light in the moving object looks like it is travelling faster than c f
  6. That's not quite what the wiki says. It does not deal with reflections, and it does make assumptions about the transit of light by drawing its vector, but that's ok. The rest only works when you deny observer S of all knowledge of his surroundings. If we allow him to understand his frame of reference and measure along his axis he can determine that the illumination of the rear took place at a distance less than L/2 from him. This creates no problems since as the train passed he saw its length as L and; because the time of observation is based on distance if we use light as our measuring tool
  7. I understand the "experiment" for sure, but I am having trouble understanding your explanation of it. The illustrations on Wikipedia are very simple, but quite incomplete if we are to consider this an "experiment". It does not consider how measurements would be taken or what would actually be seen. For example it indicates a path of light, as understood by the platform, as just stopping. The platform observer cannot see that, so this is merely imagination. We are left to assume that if there was a return path (not considered in the illustration) then the platform observer would be able t
  8. Simply because you stated "you need to compare what S and P see". This kind of communication, like email, can be confusing so perhaps I misunderstood your meaning. Where I was at was - both P & S are in identical situations, neither knows which is moving, etc., etc., you know the premises. So I was at the point where, since we can determine they perceive the same thing then I assumed you were saying it takes a third, external, observer to see a difference.
  9. Actually it's not even necessary to specify anything about the ends of the platform, it's helpful to use it, or anything representing the axes of the "experiment". I am not having a problem understanding what you are saying. You description and reference is very common and wisely used. It's not difficult to understand at all. What I am describing is an alternate way of looking at this by considering what an observer actually does see. I believe that you are not understanding my explanation of what happens when we use real world observations, and these are common everyday experiences. O
  10. Well surely the platform would represent the x axis of the observer S. You have eliminated the platform, the possibility of seeing any part of the train (only a theoretical reflection) and, of course, S cannot see what P sees because that would entail him having vision that acts faster than the speed of light. No one in this scenario can do any comparisons, so I understand that when you say "you need to compare what S and P see" you are asking that I be the observer. Let me think about this.
  11. Can you please clarify. I am now confused. As I understand it you have said we must ignore the platform, which is one of the frames. I understand P & S, and I understand the train as a frame. Why must we not take measurements on the platform since that is equally valid as a frame of reference.
  12. So both P & S can only see the train, and neither can see the platform?
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