Longitude

[Bruce Appelbaum]

     As I said in my other response, the different units were developed for 
     different applications.  The metric system, developed in the late 
     1700s or 1800s I believe, was developed in order to have a single 
     consistent set of units.  A kilometer is a kilometer, on land, sea, or 
     in space.  
     
     Other units, such as nautical miles, are often referred to as 
     "conventional units" because of their traditional origin and use.
     
     Note that the unit "kilometer" is really a meter with a prefix (kilo) 
     to indicate thousands.  A centimeter, on the other hand is a meter 
     with a prefix (centi) to indicate hundredths.  Similarly, a millimeter 
     is a meter with a prefix (milli) to indicate thousandths.  
     
     Metric prefixes are as follows:
     
     1,000,000,000,000                    10^12           tera
         1,000,000,000                    10^9            giga
             1,000,000                    10^6            mega
                 1,000                    10^3            kilo
                   100                    10^2            hecto
                    10                    10^1            deka
                      0.1                 10^-1           deci
                      0.01                10^-2           centi
                      0.001               10^-3           milli
                      0.000001            10^-6           micro
                      0.000000001         10^-9           nano
                      0.000000000001      10^-12          pico
                      0.000000000000001   10^-15          femto
     
     
     And to confuse things even further, the metric system is being 
     replaced by the (sp?) Systeme Internationale (SI), which is pretty 
     much the metric system with a bunch of different names (for famous 
     scientists) for commonly used derived units (for instance, the unit of 
     pressure is the Pascal, the unit of energy is the Joule, the unit of 
     power is the Watt, the unit of force is the Newton).
     
     As an engineer, I have to deal with varying sets of units in my work 
     -- some traditional (pounds, tons, gallons, feet, cubic feet, BTUs), 
     and some metric (kilograms, Joules, meters, cubic meters).  Lots of 
     classroom time learning the units and how to do unit conversions 
     correctly from system to system.
     
     Hope this helps
     
     


______________________________ Reply Separator _________________________________
Subject: Re: Longitude
Author:  Joe Varo <vjvaro at erie.net> at Internet
Date:    4/10/97 1:55 PM


Thanks to Murthy, Bruce and David for their clarifications of "nautical 
miles".
     
So the reason for using nautical miles in air and sea travel is that by 
these two modes of transportation you're more closely traveling along a 
perfect sphere, whereas on land you have to deal with and traverse a more 
irregular terrain?
     
Another question:  is the nautical mile part of the metric system?  Do 
pilots from countries other than the US reckon their distances in 
kilometers or nautical miles?  Is the kilometer, for some reason, equally 
accurate over both land and sea?
     
I realize that this has nothing to do with Pynchon...but who knows, it 
might be useful for M&D.