WHEN OBI WAN IS STRUCK DOWN BY DARTH VADER HE SAYS "IF YOU STRIKE ME DOWN I WILL BECOME MORE POWERFUL THAN YOU COULD EVER IMAGINE" (OR SOMETHING LIKE THAT.)
THIS PROVES THAT HE ALLOWED HIMSELF TO BE STRUCK DOWN SO THAT HE COULD "SPEAK" TO LUKE FROM BEYOND. ALSO, THE FACT THAT VADER GOES OVER TO THE ROBE AN STEPS ON IT SHOWS THAT HE IS NOT AWARE OF THE USE OF THIS FUNCTION BECAUSE HE SEEMS BAFFLED BY WHAT HAS HAPPEN TO OBI WANS BODY. I THINK YODA DID ALLOW HIMSELF TO DIE SO THAT HE TOO COULD GUIDE LUKE FROM BEYOND WITHOUT THE DANGER OF BEING STRUCK DOWN IN THE FLESH.
AFTER THIS HAPPEN, THERE IS TIME FOR THE EMPEROR AND VADER TO LEARN THIS TECHNIQUE BEFORE HE DIES IN E6. THERE IS NEVER PROOF THAT THE EMPEROR ACTUALLY DIES FROM HIS FALL DOWN THE SHAFT.....WHY WOULD THERE BE e7, e8 OR e9'S IF EVIL IS CRUSHED IN e6.
THEREFORE, I THINK THE SPRIRT THING IS TAUGHT TO THE JEDIS WITH THE HIGHEST MIDECLORIAN (SPELLING?) LEVELS. OR CANNOT BE LEARNED BY A JEDI WITH A LOWER MIDECLORIAN LEVEL. OR IS KEPT SECRET TO KEEP EVIL FROM ENTERING THIS SPIRIT FORM.
I THINK IN E3 LUCAS TRIED TO EXPLAIN THIS FUNCTION WHEN PALPETINE TELLS ANIKIN THAT HE KNOWS OF A WAY TO LIVE FOREVER.
ANOTHER QUESTION I HAVE IS WHY DOES PALPETINE AGE SO MUCH BY USING THE ELECTRIC HANDS THING?
WHATS MOST BAFFLING BY THE DEATH OF ALL THE OTHER JEDIS IS THAT FACT THAT THEY WERE KILLED BY BLASTERS. WHY WOULDNT THERE KNOWLEDGE OF THE FORCE HAVE FORESEEN THE BLASTER SHOTS MOMENTS BEFORE THE SHOTS WERE FIRED AND WHY ARE THEIR REFLEXES THEY USED SO FLAWLESSLY BEFORE, NOT ENOUGH TO SAVE THEM BY THESE WEAK ATTACKS.