Briefly explain why the invention of an accurate clock was crucial to solving the problem of determining longitude

Although accurate pendulum clocks existed in the 17th century, the motions of a ship and changes in humidity and temperature would prevent such a clock from keeping accurate time at sea. King Charles II founded the Royal Observatory in 1675 to solve the problem of finding longitude at sea.

hm, switch the relative; nominative and indefinite; objective ? not too bright in the knowledge of the english.