grelf
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I have long been puzzled by the whole idea of delayed choice experiments with photons.
In a photon's frame of reference there is no distance traveled between emission and absorption; the distance has contracted (Lorentz-Fitzgerald) to zero. More relevantly there is no time duration either (dilated to stand-still). As far as the photon is concerned there is no time interval during which anything could possibly change. Some experiments in quantum mechanics use a double-slit interferometer in which experimenters claim to change the type of detector after a photon has encountered the slits but before it reaches a detector. The experimenters' actions clearly do have an effect, explicable in terms of quantum mechanics. While this may seem fine in an experimenter's reference frame it clearly makes no sense in the frame of each photon and so such experiments need reinterpreting.
Considering one photon, two events exist in space-time: the emission and absorption events. An experimenter may feel that he has affected the 4-position of the second event during the flight of a photon but from the photon's point of view he cannot. Even if, from the experimenter's point of view, the photon was emitted in a distant galaxy, the photon "sees" only an instantaneous transfer between two events which must, from its point of view, therefore be adjacent. If the experimenter has any influence (but let's not get into discussions about free will) it is to cause a different photon connection between events even though, from his point of view, the emission event may have been in the distant past. In other words, the experimenter's choice causes a different photon to exist. This may seem shocking: the experimenter causes a different photon connection between events that appear to have been initiated a long time ago. Nevertheless it is consistent in space-time.
How else can we make any sense of such experiments?
This problem does not arise for particles with mass because they cannot reach the speed of light and so their paths will always have some duration.
In a photon's frame of reference there is no distance traveled between emission and absorption; the distance has contracted (Lorentz-Fitzgerald) to zero. More relevantly there is no time duration either (dilated to stand-still). As far as the photon is concerned there is no time interval during which anything could possibly change. Some experiments in quantum mechanics use a double-slit interferometer in which experimenters claim to change the type of detector after a photon has encountered the slits but before it reaches a detector. The experimenters' actions clearly do have an effect, explicable in terms of quantum mechanics. While this may seem fine in an experimenter's reference frame it clearly makes no sense in the frame of each photon and so such experiments need reinterpreting.
Considering one photon, two events exist in space-time: the emission and absorption events. An experimenter may feel that he has affected the 4-position of the second event during the flight of a photon but from the photon's point of view he cannot. Even if, from the experimenter's point of view, the photon was emitted in a distant galaxy, the photon "sees" only an instantaneous transfer between two events which must, from its point of view, therefore be adjacent. If the experimenter has any influence (but let's not get into discussions about free will) it is to cause a different photon connection between events even though, from his point of view, the emission event may have been in the distant past. In other words, the experimenter's choice causes a different photon to exist. This may seem shocking: the experimenter causes a different photon connection between events that appear to have been initiated a long time ago. Nevertheless it is consistent in space-time.
How else can we make any sense of such experiments?
This problem does not arise for particles with mass because they cannot reach the speed of light and so their paths will always have some duration.