▁propos als ▁by ▁cosm ological ▁hor iz ons . ▁The ▁universe ▁could ▁be ▁infinite ▁in ▁extent ▁or ▁it ▁could ▁be ▁finite ; ▁but ▁the ▁evidence ▁that ▁leads ▁to ▁the ▁infl ation ary ▁model ▁of ▁the ▁early ▁universe ▁also ▁implies ▁that ▁the ▁" total ▁universe " ▁is ▁much ▁larger ▁than ▁the ▁observable ▁universe , ▁and ▁so ▁any ▁edges ▁or ▁ex otic ▁geomet ries ▁or ▁top ologies ▁would ▁not ▁be ▁directly ▁observable ▁as ▁light ▁has ▁not ▁reached ▁scales ▁on ▁which ▁such ▁aspects ▁of ▁the ▁universe , ▁if ▁they ▁exist , ▁are ▁still ▁allowed . ▁For ▁all ▁int ents ▁and ▁purposes , ▁it ▁is ▁safe ▁to ▁assume ▁that ▁the ▁universe ▁is ▁infinite ▁in ▁spatial ▁extent , ▁without ▁edge ▁or ▁strange ▁connected ness . ▁ ▁Reg ard less ▁of ▁the ▁overall ▁shape ▁of ▁the ▁universe , ▁the ▁question ▁of ▁what ▁the ▁universe ▁is ▁expand ing ▁into ▁is ▁one ▁which ▁does ▁not ▁require ▁an ▁answer ▁according ▁to ▁the ▁theories ▁which ▁describe ▁the ▁expansion ; ▁the ▁way ▁we ▁define ▁space ▁in ▁our ▁universe ▁in ▁no ▁way ▁requires ▁additional ▁exterior ▁space ▁into ▁which ▁it ▁can ▁expand ▁since ▁an ▁expansion ▁of ▁an ▁infinite ▁exp anse ▁can ▁happen ▁without ▁changing ▁the ▁infinite ▁extent ▁of ▁the ▁exp anse . ▁All ▁that ▁is ▁certain ▁is ▁that ▁the ▁manifold ▁of ▁space ▁in ▁which ▁we ▁live ▁simply ▁has ▁the ▁property ▁that ▁the ▁distances ▁between ▁objects ▁are ▁getting ▁larger ▁as ▁time ▁goes ▁on . ▁This ▁only ▁implies ▁the ▁simple ▁observ ational ▁consequences ▁associated ▁with ▁the ▁metric ▁expansion ▁expl ored ▁below . ▁No ▁" out side " ▁or