Searching \ for '[EE] SI units - was disposable cameras' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: massmind.org/techref/index.htm?key=units+was+disposable
Search entire site for: 'SI units - was disposable cameras'.

Exact match. Not showing close matches.
PICList Thread
'[EE] SI units - was disposable cameras'
2009\07\26@151938 by Joseph Bento

face
flavicon
face

On Jul 26, 2009, at 12:01 PM, Gerhard Fiedler wrote:

> Olin Lathrop wrote:
>
>> There is enough confusion in the world, and sloppiness with units
>> causes real harm.
>
> Besides that, there is a beauty in the use of correct units. There  
> is a
> lot of thought that went into the SI system, and using it properly,  
> you
> kind of get a free ride to enjoy the beauty of these thoughts.

It's interesting to read the historical context of what a meter,  
kilogram, etc is.  I wonder if such exacting scientific definitions  
exist for foot, pound, etc., other than the length from one's nose to  
the tip of the outstretched finger.  :-)

Adaption to the SI system apparently began as early as the 19th  
century.  While we Americans have finally caught on in the science and  
technical fields, the general populace has not.

Joe

2009\07\26@164045 by olin piclist

face picon face
Joseph Bento wrote:
> It's interesting to read the historical context of what a meter,
> kilogram, etc is.  I wonder if such exacting scientific definitions
> exist for foot, pound, etc., other than the length from one's nose to
> the tip of the outstretched finger.  :-)

Remember that the foot and yard came about much earlier than the meter.  The
metric system was in part a response to the mess of units, with each little
region of Europe often having its own.  The yard and foot were standardized
somewhat long before the meter by using the king as the standard.  I'm not
sure how they then dissemminated that standard measurement.  But the point
is, people were thinking about these things and coming up with at least some
solutions long before the metric system.

Today the imperial units are defined in terms of metric ones, which are
defined against evolving standards as we discover ways to measure something
more accurately.  For example, the inch is 25.4mm exactly, by definition.
That makes the foot exactly 304.8mm, whatever a mm really is.  It used to be
1/1000 the distance between two scratches on a metal bar in Paris.  I think
it's now a certain number of wavelengths of the red emissions of Krypton 86,
but that may have changed again and I may be a bit off about it in the first
place.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\26@171144 by Joseph Bento

face
flavicon
face

On Jul 26, 2009, at 2:42 PM, Olin Lathrop wrote:

>
> Today the imperial units are defined in terms of metric ones, which  
> are
> defined against evolving standards as we discover ways to measure  
> something
> more accurately.  For example, the inch is 25.4mm exactly, by  
> definition.
> That makes the foot exactly 304.8mm, whatever a mm really is.  It  
> used to be
> 1/1000 the distance between two scratches on a metal bar in Paris.  
> I think
> it's now a certain number of wavelengths of the red emissions of  
> Krypton 86,
> but that may have changed again and I may be a bit off about it in  
> the first
> place.

Yes, and the kilogram physical iridium standard has lost something  
like 30 micrograms of its mass.  So it might seem that as time and  
millennia evolve, standards themselves may change.

While I think time and distance can be measured without a physical  
reference (as per your example), I wonder how weight measurements  
might be referenced?  I don't think the scientists have figured out a  
way to use physical constants for a weight reference.

Joe
 

2009\07\26@181745 by cdb

flavicon
face


:: The yard and foot were standardized
:: somewhat long before the meter by using the king as the standard.  
:: I'm not
:: sure how they then dissemminated that standard measurement.

This is where the term Yardstick comes from - a stick was made that
represented the official 3' 3". Same as a Chain was a physical piece
of kit.

Ah you can tell I was born in the era of Libra, Shillings and Denari.

Colin
--
cdb, spam_OUTcolinTakeThisOuTspambtech-online.co.uk on 27/07/2009

Web presence: http://www.btech-online.co.uk  

Hosted by:  http://www.1and1.co.uk/?k_id=7988359







2009\07\26@190711 by Gerhard Fiedler

picon face
Joseph Bento wrote:

> While I think time and distance can be measured without a physical  
> reference (as per your example), I wonder how weight measurements  
> might be referenced?  I don't think the scientists have figured out a  
> way to use physical constants for a weight reference.

See also
<http://en.wikipedia.org/wiki/SI_base_unit#Proposal_to_modify_the_definitions>

Gerhard

2009\07\26@210338 by Peter Wilson

flavicon
face
Couldn't let this pass ..

A yardstick is a yard which is 3' (3 feet) -  3' 3" is a approximation
of a meter.

Interestingly a chain was a surveyors chain which comprised 100 links
and was 22 yards long. A link was used as a measurement - 100 links to
the chain.

Yep - I've learned both imperial and metric

Peter W



cdb wrote:
{Quote hidden}

2009\07\26@214330 by cdb

flavicon
face


:: Couldn't let this pass ..
::
:: A yardstick is a yard which is 3' (3 feet

Whoopsy, school was so long ago :), but then I did tell someone the
other day a guinea was 30/- instead of 21/-.

:: nterestingly a chain was a surveyors chain which comprised 100
:: links and was 22 yards long

Imperial measurements are just not cricket! Or are they? :)

A rarely used unit of measurement is the Nail, I think it was 2 inches
to a nail.

Colin
--
cdb, colinspamKILLspambtech-online.co.uk on 27/07/2009

Web presence: http://www.btech-online.co.uk  

Hosted by:  http://www.1and1.co.uk/?k_id=7988359







2009\07\27@082805 by Carl Denk

flavicon
face
The surveyor's chain was subject to wear between the links, and could
become longer. In the USA, there are scattered around the country,
accurately spaced monuments, where a surveyor, or others can check the
length of there linear measuring devices. In my earlier years, used one
located in the lower level of a county courthouse. Was a pair of brass
rods with center punch marks in the marble floor. Early surveyors used
magnetic compasses, and it was important to know whether he was left or
right handed. The steel sidearm (gun) would affect the compass.

Peter Wilson wrote:
{Quote hidden}

More... (looser matching)
- Last day of these posts
- In 2009 , 2010 only
- Today
- New search...