Discussion:
Why are there nautical miles but no nautical kilome
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BurfordTJustice
2018-10-11 12:09:19 UTC
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Aww the mouth of the north tundra..

A nautical mile is a unit of measurement defined as exactly 1,852 metres.
Historically, it was defined as one minute of latitude, which is equivalent
to one sixtieth of a degree of latitude.

From lefty wiki even....

https://en.wikipedia.org/wiki/Nautical_mile



"Clare Snyder" <***@snyder.on.ca> wrote in message news:***@4ax.com...
: On Wed, 10 Oct 2018 23:41:03 -0400, micky <***@bigfoot.com>
: wrote:
:
: >
: >This is from Wikip's article on Gemini 8:
: >
: >Perigee (min): 159.8 kilometers (86.3 nautical miles)
: >
: >Why are there nautical miles but no nautical kilometers?
:
:
: Why shouldthere be? A naughtical mile is equivalent to 1 degree of
: latitude. A statute mile is an arbitrary measurement.
: The origins of the meter go back to at least the 18th century. At that
: time, there were two competing approaches to the definition of a
: standard unit of length. Some suggested defining the meter as the
: length of a pendulum having a half-period of one second; others
: suggested defining the meter as one ten-millionth of the length of the
: earth's meridian along a quadrant (one fourth the circumference of the
: earth). In 1791, soon after the French Revolution, the French Academy
: of Sciences chose the meridian definition over the pendulum definition
: because the force of gravity varies slightly over the surface of the
: earth, affecting the period of the pendulum.
:
: Why add another arbitrary measurement to the mix????
Brian Reay
2018-10-11 12:53:28 UTC
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Post by BurfordTJustice
Aww the mouth of the north tundra..
A nautical mile is a unit of measurement defined as exactly 1,852 metres.
Historically, it was defined as one minute of latitude, which is equivalent
to one sixtieth of a degree of latitude.
From lefty wiki even....
https://en.wikipedia.org/wiki/Nautical_mile
For completeness, it is the distance at the subtended by 1 minute of
latitude.

For those less familiar with maths, or geometry really, think of a slice
of Pie*. The angle at the point (the small angle, between the sides)
would by 1 minute, or 1/60 of a degree, and the curve is the arc
subtended by that angle.

Out of interest, the Knot (the Nautical unit of speed), is Nautical
Mile/ Time. 1 Knot being 1 nmile/hour.

*The Pie is on is edge.

They used latitude rather than longitude as with the later, the arc
subtended decreases in length as you move north or south of the equator.

The kilometer was also, originally, defined by using the Earth but, of
course, more 'modern' techniques are now used. There was also, I
believe, a 'standard' 1m rod somewhere which has also been superseded.

The history of navigation is really rather interesting and well worth
reading about. Finding latitude was, relatively, easy but finding
longitude provided more challenging until Harrison perfected an accurate
time piece.

(In my engineering days I worked on navigation systems, among other things.)
Post by BurfordTJustice
: >
: >
: >Perigee (min): 159.8 kilometers (86.3 nautical miles)
: >
: >Why are there nautical miles but no nautical kilometers?
: Why shouldthere be? A naughtical mile is equivalent to 1 degree of
: latitude. A statute mile is an arbitrary measurement.
: The origins of the meter go back to at least the 18th century. At that
: time, there were two competing approaches to the definition of a
: standard unit of length. Some suggested defining the meter as the
: length of a pendulum having a half-period of one second; others
: suggested defining the meter as one ten-millionth of the length of the
: earth's meridian along a quadrant (one fourth the circumference of the
: earth). In 1791, soon after the French Revolution, the French Academy
: of Sciences chose the meridian definition over the pendulum definition
: because the force of gravity varies slightly over the surface of the
: earth, affecting the period of the pendulum.
: Why add another arbitrary measurement to the mix????
--
Smile for the camera ;-)

Remarkable Coincidences:
The Stock Market Crashes of 1929 and 2008 happened on the same
date in October. In Oct 1907, a run on the Knickerbocker Trust
Company led to the Great Depression.
R. Mark Clayton
2018-10-11 15:02:26 UTC
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Post by BurfordTJustice
Aww the mouth of the north tundra..
A nautical mile is a unit of measurement defined as exactly 1,852 metres.
Historically, it was defined as one minute of latitude, which is equivalent
to one sixtieth of a degree of latitude.
From lefty wiki even....
https://en.wikipedia.org/wiki/Nautical_mile
: >
: >
: >Perigee (min): 159.8 kilometers (86.3 nautical miles)
: >
: >Why are there nautical miles but no nautical kilometers?
You answered it yourself below.
Post by BurfordTJustice
: Why shouldthere be? A naughtical mile is equivalent to 1 degree of
: latitude. A statute mile is an arbitrary measurement.
: The origins of the meter go back to at least the 18th century. At that
: time, there were two competing approaches to the definition of a
: standard unit of length. Some suggested defining the meter as the
: length of a pendulum having a half-period of one second; others
: suggested defining the meter as one ten-millionth of the length of the
: earth's meridian along a quadrant (one fourth the circumference of the
: earth). In 1791, soon after the French Revolution, the French Academy
: of Sciences chose the meridian definition over the pendulum definition
: because the force of gravity varies slightly over the surface of the
: earth, affecting the period of the pendulum.
: Why add another arbitrary measurement to the mix????
Because everything has to be different in France, so they invented their own units. They did quite a decent job considering and most of their units except time were formed into what is now the SI system. It was largely decimal, so as stated there are 10**7 m in 90 degrees on the earth's surface (10,000km) whereas a nautical mile is 1/5400 of the same distance.

It is not quite exact as the original metre was slightly miscalculated.

Metric mass, area and volume, force and other units are derived from the length - e.g. 1 tonne is the mass / weight of a cubic metre of water.



The decimal calendar was abandoned soon after Robespierre's time, although decimal time partly survived - I have an old [French or Belgian] stop watch dual marked in seconds and hundredths of a minute.
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