Question

To measure longitude, one needs

A) to measure angles in the sky.
B) to have a very accurate clock.
C) to have a way to communicate instantly with someone at different longitude.
D) all of the above

Answer 1

To measure longitude, you need a very accurate clock set to Greenwich Mean Time, as the longitudinal difference is calculated based on time differences from GMT. The correct answer to the student's question is B) to have a very accurate clock.

Step-by-step explanation:

Measuring longitude requires a very accurate clock set to Greenwich Mean Time (GMT). Longitude is measured by calculating the time difference between your current location and GMT. If, for instance, you determine that it's noon where you are and your clock shows it's 3 p.m. GMT, you are at 45 degrees west longitude because there's a 15-degree change in longitude for every hour's difference in time from GMT. The work of John Harrison, an English clockmaker, was foundational in solving the problem of measuring longitude at sea, contributing to navigation technology with his accurate marine chronometers.