Kizarvexis wrote:...
Safeholdians have pocket watches and use them to time attacks to the minute. Wouldn't that mean that a marine chronometer would already be feasible?
Pocket watches can be reset daily as all one needs to do is observe local noon. Or groups can synch watches and that works fine for a short period like timing an attack later the same day. Synching watches as a group before drills/attacks was a standard army procedure when I was a kid. An error of a minute a day is unimportant.
Mechanical marine chronometers don't seem to be around much or at least I have not seen them mentioned. We already know (forget which book) that Charisans are so good at dead reckoning on known routes that many captains prefer it to more "modern" methods. This is not at all impossible and in fact was common practice on Earth in the sailing era. For much commerce, it is perfectly acceptable: Just follow the mapped out trades and currents. The military and specialized commerce (e.g., whalers, for one, on Earth) however had more stringent needs which did require chronometers.
Marine chronometers must
maintain the noon from a standard point (Greenwich on Earth) over a long period of time
without correction. Totally different problem. Errors are cumulative and if uneven, cannot be compensated for. That is, a clock that gains or loses a known number of seconds per day is fine. In fact all did and a record of this was kept with the instrument. But uneven changes due to changing temps, various accelerations, mechanical problems from uneven care, even slightly changing the place of storage, etc. all tend to add up in unknown, uneven ways. After weeks at sea, a cumulative error of plus or minus only 4 minutes works out being somewhere east or west on a line 120 nautical miles long at the equator (a bit under 140 statute miles). An error of a minute a day would be disastrous.
Feasible? maybe. But I haven't read of anyone doing much with them. Of course OWL could build acceptable chronometers any time they were needed. Alternatively, David just may not be mentioning them as they don't concern him or the story line.
Some of the long military voyages would seem to need them, though coastal sailing with only minimal straight blue water crossings of fairly short durations seem the norm on Charis as I read the series and look at the map.