A photon is (described by) an electromagnetic wave, meaning the oscillation of the E and the B field. Now there is this single photon that comes from a faraway star and hits the CCD detector of some astronomical satellite. As an approximation consider that it traveled through vacuum for the last several million years since it was send out by some start. Just before the photon shoves it energy into the CCD and is recorded, what is the qualitative description of the E and the B field. I would be interested in statements like - The fields are nearly/completely zero outside a radius of ... around the position just in front of the CCD. - 99% of the fields' energy is concentrated just in front of the CCD. Or, to the contrary something like. - The fields are spread far over the cosmos, roughly in a sphere around the star that emitted the photon. - Only when the photon is actually registered by the CCD, the collapse of the wave function instantly sucks the whole energy, just previously spread over this sphere, into the CCD. Or any other description that gives a qualitative idea of where this photons is "located" just before it hits the CCD. Thanks, Harald.