This is by far the strangest and most thought provoking experiments in physics! The data from this experiment has caused some to say that the delayed choice to observe or not observe the path of the idler photon will change the outcome of an event in the past.
The past being represented by the detector D zero! But I believe the data only highlights that we have no fundamental understanding of why we have a past that can never be changed and a future that is always uncertain. This video will explain a logical explanation of this experiment using a new theory in which light is a wave and only a particle when it comes in contact with the electrons of an object. This forms an interactive process with new photons continuously being formed relative to the position and momentum of the atoms.
In this theory the wave particle duality of light is acting like the bits or zeros and ones of a computer.
This forms an interactive process continuously forming a blank canvas that we can interact with turning the possible into the actual! This theory explains a greater reality of one creative principle behind the laws of physics forming something like the sounding board of a musical instrument that resonates with the vibrations of one's own thoughts, efforts and actions! Time can be explained as an emergent property with Heisenberg's Uncertainty Principle ∆×∆p(xyz)≥h/4π representing the same uncertainty we have with any future event at the smallest observerable level. This process is unfolding within an infinite number of dynamic interacting reference frames that are continuously coming into existence replacing previous reference frames as they become part of the past and what we call history. Each detector in the experiment has it own reference frame relative to the photon energy. This theory can be linked to Einstein’s time dilation in Relativity, the greater the energy the greater the Lorentz contraction of space and time or spacetime! This theory is just saying that this process works with a photon of energy making time an emergent property within the experiment.