▁Lap lace . ▁Its ▁subsequent ▁development ▁has ▁inter w oven ▁a ▁variety ▁of ▁scientific ▁discipl ines ▁including ▁astronom y , ▁physics , ▁ge ology , ▁and ▁planet ary ▁science . ▁Since ▁the ▁dawn ▁of ▁the ▁space ▁age ▁in ▁the ▁ 1 9 5 0 s ▁and ▁the ▁discovery ▁of ▁ex tras olar ▁plan ets ▁in ▁the ▁ 1 9 9 0 s , ▁the ▁model ▁has ▁been ▁both ▁challeng ed ▁and ▁ref ined ▁to ▁account ▁for ▁new ▁observations . ▁ ▁The ▁Sol ar ▁System ▁has ▁evol ved ▁consider ably ▁since ▁its ▁initial ▁formation . ▁Many ▁mo ons ▁have ▁formed ▁from ▁cir cling ▁disc s ▁of ▁gas ▁and ▁dust ▁around ▁their ▁parent ▁plan ets , ▁while ▁other ▁mo ons ▁are ▁thought ▁to ▁have ▁formed ▁independently ▁and ▁later ▁been ▁captured ▁by ▁their ▁plan ets . ▁Still ▁others , ▁such ▁as ▁Earth ' s ▁Moon , ▁may ▁be ▁the ▁result ▁of ▁giant ▁coll isions . ▁Coll isions ▁between ▁bodies ▁have ▁occurred ▁contin ually ▁up ▁to ▁the ▁present ▁day ▁and ▁have ▁been ▁central ▁to ▁the ▁evolution ▁of ▁the ▁Sol ar ▁System . ▁The ▁positions ▁of ▁the ▁plan ets ▁might ▁have ▁shift ed ▁due ▁to ▁gravit ational ▁interactions . ▁This ▁planet ary ▁migration ▁is ▁now ▁thought ▁to ▁have ▁been ▁responsible ▁for ▁much ▁of ▁the ▁Sol ar ▁System ' s ▁early ▁evolution . ▁ ▁In ▁roughly ▁ 5   b ill ion ▁years , ▁the ▁Sun ▁will ▁cool ▁and ▁expand ▁out ward ▁to ▁many ▁times ▁its ▁current ▁diameter ▁( be coming ▁a ▁red ▁giant ), ▁before ▁casting ▁off ▁its