Here is a thought experiment which is a modified version of a one I posted 4 years ago. A moving train, where there are two slits at an equal distance from a photon source along the direction of motion open for a short period of time to allow the entry of photons from the source. The source emits one photon at a time. The two slit are closed before and after the photon approaching them. For the train observer, an interference pattern will form. However, for the ground observer, the sequence as follows; the rear slit opens and closes then the near slit opens and closes. Now, for the ground observer, the photon will only see one slit opens which mandates an outcome to be the same as a single slit experiment with no formation of any interference pattern. I posted a similar thread in 2012 https://www.physicsforums.com/threads/interference-pattern-versus-sr.567738/page-7. At the end, I was convinced that what matters, is the coincidence of paths of two photons at the screen no matter whether the two slits open at the same time or no. But here, only one photon is emitted at a time, so there is no paths to coincide on the screen. What makes the interference pattern is the two wave-functions of the photon. but the wave-function possess no physical reality and no such thing like a path of a wave-function which means no physical coincidence happen on the screen.