"Nick Mueller" wrote in message
...
Ed Huntress wrote:

Ha! Well, I wouldn't go that far. I'd say that they have had mixed
success
in "cleaning up" the metric system itself. There are units that are in
common use (kgm, for kilogram [mass]; calorie; liter; micron), for the
same reason many of our inch/Imperial units are in common use: they
relate
to experience of the senses, or they apply a single dimension to a
commonly used unit when the SI demands multiple-dimension units.

Ah, you are confusing things!
SI-units are the smallest possible set of units to do all the
calculations.

Yes, we've established that.

Metric units are based on the SI-units.

Uh, it was the other way around, Nick. Metric units existed long before the
SI.

They do have a few "shortcuts" like
the liter or bar (= kPa). F.e., the liter is clearly derived from SI (1
dm^3). But nothing like kgm, as kg is already mass.

Well, this is a good example of what I've been talking about. The definition
of a kilogram is meaningless to non-scientists who have to use the quantity
in everyday life. The meaningful quantity is the force that's exerted on a
kilogram of mass by gravity. That's the one they can feel, that's the one
that's consequential in their lives and work, and that's the one everyone
(except scientists) relates to.

Thus, the kgm remains the *sensible* unit. The "proper" definition of the
kilogram is an abstraction that is essentially meaningless if you don't have
a laboratory.

The micron is not a new unit, it is just an lazy abbrev. of micrometer
(µm).

In the US, and possibly in the UK, we avoid the use of "micrometer" because
of possible ambiguity. For example, the sentence "We measured the length of
the screw to the accuracy of a micrometer."


Some old non-SI-non-metric units seem to be more persistent. Like calorie
or
HP. Calorie only for nutrition, HP almost only for cars.

True enough.


And coming back to SI and liter. As soon as you do make math with it, the
liter gets unhandy. So you'll convert it as soon as you write down its
value.
Example, that also shows the advantage of the factors-of-ten-thing:
Volume = 4.2 l = 4.2 dm^3 = 4.2 * 10^-3 m^3

And an example (verbose) to do math with the units:
If I want to know the height of water poured onto 1m^2 (with the values
from
above)

height = Volume / area = 4.2 * 10^-3 m^3 / 1 m^2
Units: m^3 / m^2 = m^3 * m^-2 = m
Result: 4.2 * 10^-3 m = 4.2 mm

That's elegant! No pocket calculator involved.

Yes, it's elegant, and very useful if you have to do such calculations and
you know what you're doing. Most people don't. Thus, they avoid those
multi-dimensional units and use the single-dimensional units that the SI
doesn't like.

I'm tempted to summarize what we've been saying but it would be too
involved. The point is that the SI has been a big disappointment to those
who thought it would take over completely for other measuring systems. There
are several reasons it hasn't, the primary ones being the clumsiness of
multi-dimensional units when all you're doing is adding and subtracting them
(the vast majority of everyday calculations); the fact that the
multi-dimensional units tend not to have an analogy that can be experienced
by the senses; and the fact that for dimensional and volumetric measurement,
experience has shown that it rarely matters what base you use for units.

Thus, the SI remains the province of most scientists and many engineers,
while the older metric and the inch/Imperial system cruise merrily along,
with no apparent hardship for anyone except those SI advocates who can't
understand why the rest of the world isn't so clear-headed and sensible as
they are. d8-)

--
Ed Huntress

Ed Huntress wrote:

Thus, the kgm remains the *sensible* unit.

This is **pure** **bull-******.
Repeating it after being told that it is wrong only explains the other
nonsense you told about SI and metric.

kg *IS* *MASS*!
http://en.wikipedia.org/wiki/Kg


EOD,
Nick
--
The lowcost-DRO:
http://www.yadro.de

"Nick Mueller" wrote in message
...
Ed Huntress wrote:

Thus, the kgm remains the *sensible* unit.

This is **pure** **bull-******.
Repeating it after being told that it is wrong only explains the other
nonsense you told about SI and metric.

kg *IS* *MASS*!
http://en.wikipedia.org/wiki/Kg

We overlapped in messages. I said, "sorry, I meant kilogram-force."

--
Ed Huntress

On Mon, 24 Sep 2007 09:43:25 -0400, "Ed Huntress"
wrote:



I'm tempted to summarize what we've been saying but it would be too
involved. The point is that the SI has been a big disappointment to those
who thought it would take over completely for other measuring systems. There
are several reasons it hasn't, the primary ones being the clumsiness of
multi-dimensional units when all you're doing is adding and subtracting them
(the vast majority of everyday calculations); the fact that the
multi-dimensional units tend not to have an analogy that can be experienced
by the senses; and the fact that for dimensional and volumetric measurement,
experience has shown that it rarely matters what base you use for units.



NITPICK

kg==single dimensioned unit
m==single dimensioned unit
s==single dimensioned unit

Just about all of the rest (Ampere, Tesla, Newton, Stokes, Joule etc. ad
infinitum are multi-dimensional.

/NITPICK

Note that Nick has been just about the only one to correctly capitalise
Calorie to indicate the kilo calorie as used in food. Why aren't McDogBurgers
measured in BTU's? :-)


Mark Rand
RTFM

"Mark Rand" wrote in message
...
On Mon, 24 Sep 2007 09:43:25 -0400, "Ed Huntress"

wrote:



I'm tempted to summarize what we've been saying but it would be too
involved. The point is that the SI has been a big disappointment to those
who thought it would take over completely for other measuring systems.
There
are several reasons it hasn't, the primary ones being the clumsiness of
multi-dimensional units when all you're doing is adding and subtracting
them
(the vast majority of everyday calculations); the fact that the
multi-dimensional units tend not to have an analogy that can be
experienced
by the senses; and the fact that for dimensional and volumetric
measurement,
experience has shown that it rarely matters what base you use for units.



NITPICK

kg==single dimensioned unit
m==single dimensioned unit
s==single dimensioned unit

Just about all of the rest (Ampere, Tesla, Newton, Stokes, Joule etc. ad
infinitum are multi-dimensional.

Jeez, not *all* of them are multi-dimensional. Just enough to thicken the
whole process of using them in everyday measurements.

A lot of multi-dimensional SI units are the consequence of the system's
minimalist approach: when you use fewer base units, more of the derived
units have to combine more than one base unit.


/NITPICK

Note that Nick has been just about the only one to correctly capitalise
Calorie to indicate the kilo calorie as used in food. Why aren't
McDogBurgers
measured in BTU's? :-)

But Nick also is the one who leans on the fact that the calorie is not a
legal SI unit. d8-)

--
Ed Huntress

Mark Rand wrote:

Note that Nick has been just about the only one to correctly capitalise
Calorie to indicate the kilo calorie as used in food. Why aren't McDogBurgers
measured in BTU's? :-)


Have you ever tried to heat your house with them?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida