If Earth is orbiting the sun, the sun is orbiting the center of the galaxy, and the galaxy is hurtling through space, and the universe is expanding at an ever increasing rate, then how in the hell could a ghost stay clinged to the Earth long enough to even show up on some sketchy looking photo or say boo. Either they are subject to gravity, which makes no sense. Or somehow they can calculate these celestial movements and compensate by also hurtling through space at the same speed an angles as Earth, which sure would be a lot of effort just to throw their voice around (with no voice box to vibrate air with) every once in a while to mildly freak people out. You can believe all that, or you can believe in the human imagination, hallucinations, mental illness, and making shit up which are all common human phenomenon.