Star Wars Episode 1: The Phantom Menace - Unflamable Hair
Near the end of the movie, when Qui-Gon's body is being burned, we see everyone sitting around watching. When it shows Qui-Gon burning away, we notice all of his hair and beard and all still in tact. His hair should have burned almost immediatly, don't you think?
Well, gosh, it's a well known fact that when Jedi are initiated they learn the "force head protect" which causes their hair to act as an anti-burn protective covering, to prevent burns to the head!
(answer to anna's comment) Well, supposedly these questions are going to be answered in Episode 2. It is something having to do with the force. According to Lucas, "That's a plot point that centers around Obi-Wan saying to Vader/Anakin in the first one, 'If you strike me down, I will become more powerful than you can possibly imagine.' There is an issue about the Force and that will be revealed."
Some things have to be fudged sometimes. When you burn something it "burns" it turns all black and crinkly and stuff like that. The scene was supposed to basically provide a setting for those few conversations, not show Qui-Gon being burned and everything. and by the way, all of you forgot to notice that his clothes were still totally on and unburned.
Jedi killed in battle are to be burned. They can't disappear because they actualy died.
Only the jedi who feel their bodies became too weak to continue living organicaly, transform to a new being.
Their spirits become a new entity, represented to us as transparent holograms, like at the end of 'Return of the Jedi'.
They are still alive, but in another form.
They can give guidence to their padawans, but they no more serve as jedi.
They become part of the Force.