metric system newsgroup call for votes #1

On Fri, 14 Nov 2003 19:01:01 -0800, "Tarver Engineering"
wrote:


"Pat Norton" wrote in message
m...
Gene Nygaard wrote:
Old law defined the Admiralty mile as 6080 ft.
Old law defined the foot as 0.3048 m.
That "provide the courts with metric values for imperial units
used in the text of old laws."

Yes. But that requires an imperial to imperial conversion. The law is
merely a look up table of imperial to metric conversions.

Yep, clueless technocrats with a calculator, but the Earth is still made up
of nautical miles; legally and navigationally.--++

So what happened to the papal bull, Tarver?

Too much trouble to keep track of the day's story, so you just make up
a new one every time you post?

So what purpose is served by introducing a new,
significantly different definition?

Good question. I don't know. Perhaps the old value was wrong.

The science got better.

But these advances in science only revealed themselves to the British
lawmakers, so they are the only one who changed the nautical mile to
1853 m. Likely story!

Exactly what did they learn in 1995 which made them think that 1853 m
is better than the 1852 m adopted by the hydrology conference in 1929,
the value adopted by the United States in 1954, and by pretty much
everybody everywhere in the world outside the United Kingdom?

Exactly what did they learn in 1995 which made them think that 1853 m
is better than the 6080 British ft the British had adopted even before
1929, or the 6080.2 U.S. feet that the United States used until 1954?

One that still leaves you out of step with the
rest of the world??

The UK is in step with the rest of the world because it uses the same
international nautical mile of 1852 m that the US and everybody else
uses. The old unit is listed just in case somebody finds it in an old
piece of text. Their lawyers will not then spend time disputing the
regional effects of non-spherical abberations like we do in this
newsgroup.

Nugaard is just confused.

And what about that implicit official definition of an hour?

The problem is not the hour. The problem is comparing two imperial to
metric conversion factors that are not as precise as they could be.
This is common in conversion references.

Pat, that particular conversion reference carries other conversions to
14 digits in the case of the dram (dram gram 1.7718451953125 grams)
and to 15 digits in the case of the "ton-force" (ton-force kilonewton
9.96401641818352) and 17 digits in the case of the foot-pound force.
It carries the conversions of the British thermal unit and the therm
to 15 digits, and nobody is going to have any measurements that use
more than 6 of them.

But while the old Admiralty mile could be expressed exactly with only
7 digits, they redefined one with only 4 digits. The knot conversion
is carried to enough places so that you can see that it differs from
what it would be if that 1853 m for the nautical mile were in fact a
new definition.

All of the other figures are exact, except for the conversion from
foot-candles to lux, which is the same as converting from square
meters to square feet. That one has 15 digits, and the conversion for
knots ought to be the same.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

Gene Nygaard wrote
The problem is comparing two imperial to
metric conversion factors that are not as
precise as they could be.

So those aren't definitions after all.

They are definitions. We just have to accept that:
1 UK knot = (1 UK nautical mile + 172 mm) per hour


Exactly what did they learn in 1995 which made them
think that 1853 m is better than the 1852 m adopted
by ... everybody

The value of 1852 m is also adopted by the UK. The definition of the
'UK nautical mile' of 1853 m is for interpretation of historical text
written in the time before the UK accepted the international value.


Exactly what did they learn in 1995 which made them
think that 1853 m is better than the 6080 British ft
the British had adopted

1. The nautical mile is supposed to provide an approximation of 1
minute of angle.
2. Because of non-spherical abberations of the earth, the
approximation can be wrong by tens of metres. Anyone that attempts to
obtain more precise distances could get into big trouble if they do
not know that.
3. The international value is based on the average over the whole
planet.
4. The UK value is calculated in a different way. I seem to remember
it being the value in the English channel, but do not quote me. So
1853 m might actually be nearer to the true value than 1853.172 m
5. Given that the true value at any point varies by tens of metres,
they may have rejected the idea of maintaining mm precision. The
question then becomes why did they abandon the precise relationship
with the knot.

Just some thoughts.


But while the old Admiralty mile could be expressed
exactly with only 7 digits, they redefined one with
only 4 digits.

Quite. I really don't know the answer.

"Pat Norton" wrote in message
...
Gene Nygaard wrote
The problem is comparing two imperial to

1853 m might actually be nearer to the true value than 1853.172 m
5. Given that the true value at any point varies by tens of metres,
they may have rejected the idea of maintaining mm precision. The
question then becomes why did they abandon the precise relationship
with the knot.

Of course, only an technocrat would want to make mm measurements over a
minute of arc. It is as though Gene's mother is also his aunt.