The Longitude Problem

A matter of time

An interactive lesson with 8 steps, about 7 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Earth turns 15° per hour, so longitude = time difference × 15°.
• Finding longitude needs an accurate clock keeping home time.
• Harrison’s marine chronometers solved the problem in the 1760s.

Steps

1. Earth as a clock
2. Noon travels west
3. Local noon
4. Going west
5. The cost of a slow clock
6. A clock in the sky
7. Time is longitude
8. Harrison’s accuracy