My current view is that they are vibrations (energy), and as such exist at all times / places.
When we sense a vibration, we are connecting now to someone or something at the point at which it was physical. We connect to it in the same way that we connect to certain types of people, because they have something in common with us, or reflect us in some way.
That theory raises many more questiosn than it answers, but it makes sense to me in a simplistic way
