The two-body escape velocity (if the moon and the projectile were the only things in the universe, would the projectile’s trajectory be unbounded?) is easy to define and calculate, so when you see a single number quoted as “the” escape velocity from a location it’s usually using the two-body definition.
undercoveryankee t1_j24urhq wrote
Reply to comment by IsraelZulu in A *dumb* question, for a mixup by Independent-Choice-4
The two-body escape velocity (if the moon and the projectile were the only things in the universe, would the projectile’s trajectory be unbounded?) is easy to define and calculate, so when you see a single number quoted as “the” escape velocity from a location it’s usually using the two-body definition.