▁cosm ological ▁constant ▁into ▁his ▁theories ▁to ▁balance ▁out ▁the ▁contra ction , ▁in ▁order ▁to ▁obtain ▁a ▁static ▁universe ▁solution . ▁But ▁in ▁ 1 9 2 2 ▁Alexander ▁Fried mann ▁derived ▁a ▁set ▁of ▁equations ▁known ▁as ▁the ▁Fried mann ▁equations , ▁showing ▁that ▁the ▁universe ▁might ▁expand ▁and ▁present ing ▁the ▁expansion ▁speed ▁in ▁this ▁case . ▁The ▁observations ▁of ▁Ed win ▁Hub ble ▁in ▁ 1 9 2 9 ▁suggested ▁that ▁distant ▁galaxies ▁were ▁all ▁apparently ▁moving ▁away ▁from ▁us , ▁so ▁that ▁many ▁scient ists ▁came ▁to ▁accept ▁that ▁the ▁universe ▁was ▁expand ing . ▁ ▁Hub ble ' s ▁concerns ▁over ▁the ▁rate ▁of ▁expansion ▁While ▁the ▁metric ▁expansion ▁of ▁space ▁appeared ▁to ▁be ▁imp lied ▁by ▁Hub ble ' s ▁ 1 9 2 9 ▁observations , ▁Hub ble ▁disag re ed ▁with ▁the ▁expand ing - un iverse ▁interpretation ▁of ▁the ▁data : ▁ ▁Hub ble ' s ▁ske ptic ism ▁about ▁the ▁universe ▁being ▁too ▁small , ▁dense , ▁and ▁young ▁turned ▁out ▁to ▁be ▁based ▁on ▁an ▁observ ational ▁error . ▁Later ▁investig ations ▁appeared ▁to ▁show ▁that ▁Hub ble ▁had ▁confused ▁distant ▁H ▁II ▁regions ▁for ▁C ep heid ▁variables ▁and ▁the ▁C ep heid ▁variables ▁themselves ▁had ▁been ▁in app ropri ately ▁l ump ed ▁together ▁with ▁low - l um inos ity ▁R R ▁Ly ra e ▁stars ▁causing ▁cal ibration ▁errors ▁that ▁led ▁to ▁a ▁value ▁of ▁the ▁Hub ble ▁Constant ▁of ▁approximately ▁ 5 0 0 ▁km /