[HN Gopher] Sunstone (medieval)
       ___________________________________________________________________
        
       Sunstone (medieval)
        
       Author : benbreen
       Score  : 77 points
       Date   : 2022-12-26 20:41 UTC (3 days ago)
        
 (HTM) web link (en.wikipedia.org)
 (TXT) w3m dump (en.wikipedia.org)
        
       | Jun8 wrote:
       | You can buy a birefringent
       | (https://en.m.wikipedia.org/wiki/Birefringence) calcite crystal
       | that are often sold at rock shops and give it a try.
        
       | eschulz wrote:
       | It's interesting to consider how such a navigational instrument
       | could have been more reliable than a compass in the far north
       | where magnetic deviation becomes a serious concern, but where
       | incredibly long summer days provide an opportunity for a trained
       | sunstone navigator to shine (pun intended).
        
         | simonh wrote:
         | That's possible. I'm not an expert on navigation, but given
         | that people didn't have accurate maps, magnetic deviation might
         | not have been as much of a problem. When leaving a port you
         | only need to know what compass heading to follow to reach your
         | destination, which you can learn by trial and error, and
         | regardless of moderate magnetic deviations there will always be
         | one such. It might not take you on an optimal route, but that's
         | less important than that it gets you there reliably.
        
           | StopHammoTime wrote:
           | Magnetic deviation might not have been an problem in a single
           | year, but magnetic drift can be quite impactful even over a
           | decade. It can be quite severe the further North you get
           | which can really throw compass directions off. The airport in
           | Fairbanks, Alaska changed its runway numbers in 2009 and will
           | change then again in 2033[1]. This can represent anywhere
           | between a 15-30 degree drift over the course of 20 years.
           | 
           | For anything more than a short jaunt (which you probably
           | don't need a compass for anyway), you would need to
           | understand updated magnetic deviation regularly to navigate
           | with confidence.
           | 
           | [1] https://www.ncei.noaa.gov/news/airport-runway-names-
           | shift-ma...
        
             | olddustytrail wrote:
             | I had no idea runway numbers worked like that. Thanks!
        
           | Sharlin wrote:
           | I don't think so when the magnetic deviation can vary
           | considerably over the course of a single leg, as it does near
           | the geomagnetic poles.
        
           | [deleted]
        
       ___________________________________________________________________
       (page generated 2022-12-29 23:01 UTC)