. ▁ ▁The ▁proposed ▁field ▁and ▁its ▁quant a ▁( the ▁sub atomic ▁particles ▁related ▁to ▁it ) ▁have ▁been ▁named ▁infl aton . ▁If ▁this ▁field ▁did ▁not ▁exist , ▁scient ists ▁would ▁have ▁to ▁propose ▁a ▁different ▁explanation ▁for ▁all ▁the ▁observations ▁that ▁strongly ▁suggest ▁a ▁metric ▁expansion ▁of ▁space ▁has ▁occurred , ▁and ▁is ▁still ▁occurr ing ▁much ▁more ▁slowly ▁today . ▁ ▁Over view ▁of ▁metrics ▁and ▁com oving ▁coordinates ▁▁ ▁To ▁understand ▁the ▁metric ▁expansion ▁of ▁the ▁universe , ▁it ▁is ▁helpful ▁to ▁discuss ▁briefly ▁what ▁a ▁metric ▁is , ▁and ▁how ▁metric ▁expansion ▁works . ▁ ▁A ▁metric ▁defines ▁the ▁concept ▁of ▁distance , ▁by ▁stating ▁in ▁mathematical ▁terms ▁how ▁distances ▁between ▁two ▁nearby ▁points ▁in ▁space ▁are ▁measured , ▁in ▁terms ▁of ▁the ▁coordinate ▁system . ▁Co ordinate ▁systems ▁locate ▁points ▁in ▁a ▁space ▁( of ▁whatever ▁number ▁of ▁dimensions ) ▁by ▁assigning ▁unique ▁positions ▁on ▁a ▁grid , ▁known ▁as ▁coordinates , ▁to ▁each ▁point . ▁Lat itude ▁and ▁longitude , ▁and ▁x - y ▁graphs ▁are ▁common ▁examples ▁of ▁coordinates . ▁A ▁metric ▁is ▁a ▁formula ▁which ▁describes ▁how ▁a ▁number ▁known ▁as ▁" distance " ▁is ▁to ▁be ▁measured ▁between ▁two ▁points . ▁ ▁It ▁may ▁seem ▁obvious ▁that ▁distance ▁is ▁measured ▁by ▁a ▁straight ▁line , ▁but ▁in ▁many ▁cases ▁it ▁is ▁not . ▁For ▁example , ▁long ▁ha ul ▁aircraft ▁travel ▁along ▁a ▁curve ▁known ▁as ▁a ▁" gre at ▁circle " ▁and ▁not ▁a ▁straight ▁line , ▁because ▁that ▁is