So I asked this question in another thread but thought the question was probably best asked here in this forum to at least understand part of the experiment. My idea follows the traditional train and platform analogy that is used in many thought experiments to explain the issue of simultaneity, however this time I wish to include the double slit experiment. Since we know that the speed of light remains the same for all observers at rest and speeds of constant velocity, I was curious to know if performing the double slit experiment under these conditions would present some problems and perhaps even contradictions in results. Now as I mentioned elsewhere I'm not educated in QM nor SR so please excuse me if there's any errors in my logic or flaws in the structure of my experiment, if there is please point them out and I'd love to understand this idea in more detail, even if my conclusions are wrong. - John is standing on the platform - Emma is standing on the moving train - On the train Emma has the apparatus for the double slit experiment - At a specific moment in time as the train passes through the station, both observers witness a particle of light which is fired down the line of the train towards the two slits - There are other variables we can consider later in the description of the experiment, such as the presence and location of detectors which verify which slit the photon went through My idea is this. Since the speed of light is the same for all observers, the single photon which is fired down the line towards the double slits will be at different positions of space relative to the train for each observer. For Emma the particle of light will travel towards the apparatus at the speed of light, it will pass through the slits and will hit the detector at a specific time. For John, since the train is moving down the tracks, the particle of light will travel at the speed of light however will always remain slightly behind the particle which Emma observes. The time in which the photon passes through the slits and hits the back plate will not be simultaneous in both frames of reference. Am I right here? I don't want to go any further yet as I did in the other thread as thinking on it there are other things to consider, such as time dilation and length contraction. Could either of these factors allow the particle to hit the back plate simultaneously in both frames of reference? My idea is that perhaps with the inclusion of a detector, not only would the times in which the photon passes through the slits not be simultaneous, but also the time in which the wave function collapses as its path is verified by the presence of a detector.