What technological advancement allowed Captain Cook to calculate longitude at sea?

The marine chronometer was a pivotal technological advancement that enabled Captain Cook and other navigators of his time to accurately calculate longitude at sea. Before the invention of reliable timekeeping devices, sailors struggled with determining their east-west position because longitude requires precise timekeeping to compare the local time to the time at a reference location, typically at sea, such as Greenwich, England.

The marine chronometer provides an accurate time reference by maintaining a consistent count of time, regardless of the ship's movement or environmental conditions. This allowed sailors to determine how many degrees of longitude they had traveled by calculating the difference in time between their local noon (when the sun is at its zenith) and the reference time. With this information, navigators could plot their position more reliably on nautical charts.

The other options, while historically significant tools for navigation, did not specifically solve the problem of calculating longitude as effectively as the marine chronometer did. The sextant and astrolabe are instruments used for measuring angles in relation to celestial bodies, which is crucial for latitude calculations but not for longitude without the assistance of a precise timekeeping method. GPS navigation, a modern advancement, fundamentally changed how navigation is conducted but did not exist during Captain Cook's era. Thus, the marine chron