▁information ▁from ▁the ▁entire ▁system ; ▁thus ▁caus ality ▁is ▁preserved . ▁ ▁The ▁experiment ▁of ▁L ij un ▁Wang ▁might ▁also ▁show ▁caus ality ▁viol ation ▁since ▁it ▁made ▁it ▁possible ▁to ▁send ▁packages ▁of ▁waves ▁through ▁a ▁bul b ▁of ▁ca es ium ▁gas ▁in ▁such ▁a ▁way ▁that ▁the ▁package ▁appeared ▁to ▁exit ▁the ▁bul b ▁ 6 2 ▁nan ose cond s ▁before ▁its ▁entry , ▁but ▁a ▁wave ▁package ▁is ▁not ▁a ▁single ▁well - defined ▁object ▁but ▁rather ▁a ▁sum ▁of ▁multiple ▁waves ▁of ▁different ▁frequencies ▁( see ▁Fourier ▁analysis ), ▁and ▁the ▁package ▁can ▁appear ▁to ▁move ▁faster ▁than ▁light ▁or ▁even ▁back ward ▁in ▁time ▁even ▁if ▁none ▁of ▁the ▁pure ▁waves ▁in ▁the ▁sum ▁do ▁so . ▁This ▁effect ▁cannot ▁be ▁used ▁to ▁send ▁any ▁matter , ▁energy , ▁or ▁information ▁faster ▁than ▁light , ▁so ▁this ▁experiment ▁is ▁understood ▁not ▁to ▁viol ate ▁caus ality ▁either . ▁ ▁The ▁phys ic ists ▁Gün ter ▁N im tz ▁and ▁Alf ons ▁St ahl hof en , ▁of ▁the ▁University ▁of ▁Kob len z , ▁claim ▁to ▁have ▁viol ated ▁Ein stein ' s ▁theory ▁of ▁relativ ity ▁by ▁transm itting ▁phot ons ▁faster ▁than ▁the ▁speed ▁of ▁light . ▁They ▁say ▁they ▁have ▁conducted ▁an ▁experiment ▁in ▁which ▁mic row ave ▁phot ons ▁tra ve led ▁" inst ant ane ously " ▁between ▁a ▁pair ▁of ▁pr isms ▁that ▁had ▁been ▁moved ▁up ▁to ▁ ▁apart , ▁using ▁a ▁phenomen on ▁known ▁as ▁quantum