▁is ▁potentially ▁confusing ▁since ▁it ▁wrong ly ▁suggests ▁that ▁the ▁big ▁b ang ▁took ▁place ▁at ▁the ▁center ▁of ▁the ▁bal lo on . ▁In ▁fact ▁points ▁off ▁the ▁surface ▁of ▁the ▁bal lo on ▁have ▁no ▁meaning , ▁even ▁if ▁they ▁were ▁occupied ▁by ▁the ▁bal lo on ▁at ▁an ▁earlier ▁time . ▁ ▁In ▁the ▁" rais in ▁bread ▁model " ▁one ▁imag ines ▁a ▁lo af ▁of ▁ra is in ▁bread ▁expand ing ▁in ▁the ▁o ven . ▁The ▁lo af ▁( space ) ▁exp ands ▁as ▁a ▁whole , ▁but ▁the ▁ra is ins ▁( gra v itation ally ▁bound ▁objects ) ▁do ▁not ▁expand ; ▁they ▁merely ▁grow ▁farther ▁away ▁from ▁each ▁other . ▁ ▁The oret ical ▁basis ▁and ▁first ▁evidence ▁ ▁Hub ble ' s ▁law ▁Techn ically , ▁the ▁metric ▁expansion ▁of ▁space ▁is ▁a ▁feature ▁of ▁many ▁solutions ▁to ▁the ▁Ein stein ▁field ▁equations ▁of ▁general ▁relativ ity , ▁and ▁distance ▁is ▁measured ▁using ▁the ▁Lor ent z ▁interval . ▁This ▁explains ▁observations ▁which ▁indicate ▁that ▁galaxies ▁that ▁are ▁more ▁distant ▁from ▁us ▁are ▁re ced ing ▁faster ▁than ▁galaxies ▁that ▁are ▁closer ▁to ▁us ▁( see ▁Hub ble ' s ▁law ). ▁ ▁Cos m ological ▁constant ▁and ▁the ▁Fried mann ▁equations ▁The ▁first ▁general ▁relativ istic ▁models ▁predicted ▁that ▁a ▁universe ▁which ▁was ▁dynam ical ▁and ▁contained ▁ordinary ▁gravit ational ▁matter ▁would ▁contract ▁rather ▁than ▁expand . ▁Ein stein ' s ▁first ▁proposal ▁for ▁a ▁solution ▁to ▁this ▁problem ▁involved ▁adding ▁a