Time in space
The race was on: for whoever discovered a way to accurately measure longitude aboard a ship would be able to control the seas --and thereby control the riches of the world!
The search for longitude at sea was one of the great quests starting in the late Renaissance. And, it was how it came to be that a 17th century nobleman named Roberto della Griva found himself aboard a ship sailing southward toward Australia in search of the Prime Meridian, in Umberto Eco’s novel Island of the Day Before.
Being obsessed by longitude, the characters in the book are also obsessed by notions of time. For to calculate longitude is, of course, to calculate time.
But to do this at sea is no easy feat, because while one only requires to know the local time at the ship's current meridian as well as what the current time is would be back at the meridian of departure (or at some fixed meridian, like, say at the Solomon Islands), this remained very difficult to accurately determine aboard ship. And inaccuracies in time would result in inaccuracies of place--as is well known.
You can see where this is going...