Possible Duplicate:
Why some Jedi disappear when they die while others don't?
gets killed by Darth Vader. Then he vanishes.
What happened there?
Where did the body go?
Possible Duplicate:
Why some Jedi disappear when they die while others don't?
gets killed by Darth Vader. Then he vanishes.
What happened there?
Where did the body go?
Obi-Wan had learned from Qui-Gon Jinn about how to maintain his identity after death and became a Force Ghost. When a dying person uses the technique to become a Force Ghost, their body vanishes.
But not even the wise Wookieepedia is able to tell us what actually happens to the body when one becomes a Force Ghost. (See the above linked article on Force Ghosts for what little information is available on the process.)
He used a technique that was re-discovered by Qui-Gon Jin to become a Force Ghost.
From the Wookieepedia page:
Death for those Jedi were different: their spirits could retain their individuality and could return as voices, dreams, or apparitions at will, so that they could help those in need of their guidance. On death, their bodies vanished; this was not the case with Qui-Gon, however, probably being a technique evolved by Obi-Wan and Yoda, under Qui-Gon's guidance.
Contrary to how it's usually stated, most people become 'One with the Force'; that is to say, they lose their individuality and consciousness, and return to being part of the 'Force.' This is not to say they are gone; all they were becomes a small aspect of the Force, basically 'remembered' by it.
Force Sensitives, however, went to The Netherworld of the Force, where they continued to exist as independent beings. Those who become Force Ghosts, however, are able to return, to some degree, to exert some influence (or provide wisdom, if not knowledge) in the Real World some time.