Re: Metric Time (was Re: Why not 13 months? (Was La Systeme Metrique))
(phaedrus@)
12 Oct 1995 00:07:22 GMT
In article <45fbqr$3kd@shore.shore.net>, Whittet <Whittet@shore.net> wrote:
>In article <45dt6q$cer@cnn.Princeton.EDU>, jrhodes@pupgg.princeton.edu says...
>>
>>In article <45chpc$skj@shore.shore.net>, Whittet@shore.net (Whittet) writes:
>>>all worked out into inches, feet, yards, rods, furlongs, chains etc;
>>>to give a geocomensurate standard of measurement which is far more
>>>precise than the meter and has withstood 5 millenia of use with
>>>very small variation.
>>
>>
>>The length of a meter is known to a very high precision.
>
>Yes, but it was supposed to have been geocommensurate, it is not
>but the foot is.
But the foot ISN'T geocommensurate.
By your figures, the circumference of the Earth at the equator is
24902.72727 miles (BTW, is that statute miles or nautical miles? I
guess it's statute, since there are 21600 nautical miles around the
equator.). That works out to be 131 486 399.9856 feet.
I checked, and it works out even IF that pattern of .7272 repeats.
Which leads me to suspect that the number above was computed from a
figure for feet/equator.
As a check, the largest of the three definitions for a nautical mile I
have (6080.20 feet, pre-1959 US standard) gives a circumference of
only 24873.545 statute miles (exactly 131 332 320 feet). The current
nautical mile is about 4 feet shorter, at 1852m, making the equatorial
circumference commensurate with the meter.
Using another method, I get the circumference of the Earth to be also
less than the figure you cite. Granted, the nautical mile method
gives commensurate feet/equators, but they are also subject to limits
of precision. The International standard of the nautical mile is
1852m, as I stated. In feet, this is 6076.11548557 (to 12 significant
figures) for 1 minute of arc on the equator, or 131244094.448 (to 12
sig figures) feet/equator, not commensurate. However, my table also
gave the naut.mi. as 6076.115ft, which leads to a foot commensurate
equator, one about 9.5 feet shorter than the 1852m nautical mile.
Where did you get your 24902.72727mi figure.
If the equator really is commensurate with the foot, then it is pure
coincidence, since, as you stated, the foot has been in use for
millenia (in one form or another), longer than the notion of a round
Earth has been popular with the foot-using population.
>
> And
>>since the foot is _defined_ in terms of the meter,
>
>The foot existed for millenia before the meter was invented. The fact
>that the foot has a metric equivalent is part of the problem we are
>discussing. Would you claim that all the things measured in feet
>before there were meters are no longer in feet?
>
>
>I don't hardly
>>see how imperial units can be"far more precise" than the meter.
>
>Well for one thing there are exactly twice as many seconds in a century
>as inches in the circumference of the earth at the equator.
>
>The circumference of the earth at the equator is 24902.72727 mi
>There are 36524 days in a century
>
>365.24 x 100 x 24 x 60 x 60/24902.72727 x 5280 x 12 x 2=1
365.24 x 100 x 24 x 60 x 60 = 3,155,673,600
24902.72727 x 5280 x 12 x 2 = 3,155,673,599.66
That these numbers are so close (and would probably be closer if the
length of the equator was very slightly longer), and that the
other methods for computing circumference I know of give significantly
lower figures makes me believe that your figure for the equatorial
circumference is made up to fit your argument. Where did you get your
figure?
I'm not accusing you of making it up. I just want to know who did?
Also, the average length of a century is not 365.24, but 365.2425,
which lengthens the century by 6 hours. Do you want an equator of
24902.8977273 miles?
And what matter does it make if a particular unit is commensurate with
the equator? How often do people measure the equator to within a
meter? For that matter, given the dynamics of the ocean, the moving
tidal bulge, etc, how would you measure the equator to within a meter?
One of the two systems under discussion has a historical link to being
defined in terms of global distances over the surface of the Earth
(and that wasn't equatorial, but pole-to-equator). It hasn't been
defined that way for at least 150 years. The other system has a
historical tie to being the average length of a man's foot, and
standardized to the foot length of a particular man. But it too
hasn't been defined that way for several centuries.
Both systems are good for measuring, which you choose to use depends
on a) what system you are most familiar with, and b) who you wish to
communicate with (and what system they use). To me, 1 cup is as good
as 250ml, and 6 inches is as handy as 15 centimeters, and 20C is as
good for me as 68F.
I personally use both systems, and have important conversion factors
memorized (important to me... I learned 31.15 grams/1 troy ounce as a
child, and I still don't know offhand grams/avoidoupois ounce
(28.something, I think)). This allows me to answer oddball questions
like "how much would a 1" sphere of 24K gold cost?" (Which actually
came up in conversation. It works out to be roughly US$1900,
depending on current gold prices. The conversion involved knowing the
formula for volume of a sphere, centimeters/inch, the density of water
in gm/cc, the specific gravity of pure gold, grams/troy ounce, and the
approximate price of gold.).
>
>Can you make an equivalent claim for the meter?
I can make the claim that at one time, about 200 years ago, the meter
was based on an erroneous measurement of the north-pole-to-equator
distance through the meridian of Paris. To within 5 parts in 10
thousand, this measurement is accurate.
However, the standard of the meter is as tied to that basis as the
standard of the foot is tied to the length of King Charles II's left
foot.
I will, however, claim that it is much easier to use 40000km than
24800miles (and even slightly easier than 25000 miles, and much more
accurate) for the equatorial distance, much easier to use 1gm/cc than
to use 62.42lb/cfu (or 0.58oz/cinch), etc.
>
>>Also, you might want to note that of those 5 millenia you claim
>>inches and feet have been used, only the last 300 years have seen
>>much scienrtific progress, and thast can be attributed, at least
>>in part, to using a sensible system of measure- SI.
>>
>>Jason
>>
>
>lets remove everything which dates back more than 300 years
>
>No reading writing or 'rithmatic for starters.
>No chemistry, metals, machines, mines, astronomy, or navigation
>No tools, building materials, you get the idea...
>
>You may not realise this but without standards of measure it
>is difficult to evaluate anything.
Both of these last arguments are silly.
>
>
>Steve
>
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