▁that ▁should ▁effect ▁its ▁speed ▁has ▁changed . ▁If ▁the ▁image ▁was ▁a ▁physical ▁object , ▁it ▁should ▁be ▁able ▁to ▁travel ▁across ▁the ▁surface ▁of ▁the ▁moon ▁at ▁the ▁same ▁speed ▁regardless ▁of ▁the ▁distance ▁of ▁the ▁observer . ▁Under standing ▁this , ▁the ▁par ado x ▁begins ▁to ▁un ra vel . ▁ ▁It ▁is ▁natural ▁to ▁visual ize ▁this ▁phenomen on ▁as ▁an ▁abund ance ▁of ▁station ary ▁phot ons ▁within ▁the ▁same ▁ray ▁of ▁light ▁creating ▁the ▁spot ▁on ▁the ▁moon . ▁To ▁allow ▁the ▁image ▁to ▁move ▁from ▁one ▁end ▁of ▁the ▁moon ▁to ▁the ▁other , ▁each ▁phot on ▁must ▁move ▁later ally ▁with ▁the ▁movement ▁of ▁the ▁projection . ▁In ▁reality ▁this ▁is ▁not ▁the ▁case , ▁the ▁ray ▁of ▁light ▁is ▁a ▁collection ▁of ▁moving ▁phot ons ▁and ▁at ▁each ▁instant ▁a ▁different ▁group ▁of ▁phot ons , ▁detected ▁by ▁the ▁obser vers ▁eye , ▁are ▁creating ▁the ▁image ▁seen ▁on ▁the ▁surface ▁of ▁the ▁moon . ▁The ▁apparent ▁later al ▁movement ▁is ▁caused ▁by ▁new ▁phot ons ▁travel ing ▁on ▁a ▁different ▁path ▁from ▁the ▁light ▁source ▁to ▁the ▁moon , ▁caused ▁by ▁the ▁rotation ▁of ▁the ▁source , ▁striking ▁an ▁adjacent ▁position ▁at ▁all ▁instances ▁during ▁the ▁rotation . ▁This ▁is ▁dep icted ▁in ▁Figure ▁ 3 , ▁the ▁movement ▁from ▁point ▁A ▁to ▁point ▁B ▁can ▁be ▁visual ized ▁by ▁a ▁collection ▁of ▁phot ons ▁each ▁trav elling ▁along ▁a ▁different ▁traject ory ▁from ▁Earth ▁to ▁the ▁moon . ▁The ▁par ado