How can light be detectable everywhere?

[sophiecentaur]

The fact that familiar processes appear to exhibit causality could just make it a difficult thing to do without. But causality may just be a 'local' thing. Newton's laws and all the others are very handy for most of our lives but that could be as far as it goes..

 

[juanrga]

All the OP wanted to know is if a single photon can hit more than one detector.

From https://www.physicsforums.com/showpost.php?p=3574503&postcount=18

If that photon is absorbed by a detector at Earth, then it was not absorbed by the a spacecraft detector and vice verse.