The offical Astral Dynamics theory on the subject is that when you die your etheric body (Which supplies energy to your various other bodies) leaves your body and merges with your astral body. It makes a certain amount of sense, but the only way we'll know for sure is to die ourselves. taaaa!!
-Nate
This is something that I've wondered about for a long time: what 'feeds' one's astral body? In other words, where does it derive astral energy for nourishment?
If the astral body derives its energy from one's physical body, then where does the astral body get it's energy from after (physical) death?
Brian