"Anything meters do, inches do better.
Pounds can do anything newtons can do."

Tune from Annie Get Your Gun

See the pound-inch thread Andrew Usher just
started. Down around post 18 (can't remember
exactly) there are wavelengths and frequencies
of different colors of light and they turn out
to be especially quick to calculate in pound-inch.

With metric you have to divide 299792458 by 7
and grunt nanometers and terahertz and stuff
like that while with pound inch it turns out
to be sweet and easy mental arithmetic. And so
I have the impression Andrew snuck in under the
metric radar and painted a mustache on the
SI monalisa and it is slightly amusing. But you
will of course make up your own mind.

Cheers,

L

QUOTE FROM ANOTHER BOARD:
I've been honing the definitions of Usher's version of pound-inch units to make them
fast and exact to express.

Pound-inch is a more modern decimal system than metric
using techniques of definition which are in the
works for metric but will probably not be finally
adopted before sometime around 2010 (proposed
frequency definition of kilogram).

Pound-inch is also a more efficient system for
calculation as the physics examples posted at
this site show. These are a collection of
problems worked both in pound inch units and in
metric to demonstrate that metric calculation
is messier. Pound-inch is purely decimal, like
metric, but also has better constants.

there are several alternative modern approaches
to defining pound-inch units. Here is one that
was recently worked out. It involves defining
a small extra time unit (trice) which is roughly
a twentieth of a second and is reserved for technical
uses like working physics problems
(ordinarily time continues being told in the
usual hours minutes etc.)

1. the extra (trice) time unit is exactly 1/19.67 second.

2. the inch is defined by requiring that the
standard speed of light be exactly 600 million
inch per trice.

3. the pound force is defined by requiring that
Planck's h constant be exactly 11.51E-32 inchpound trice.

It turns out that the unit acceleration of
one inch per trice per trice is similar in
size to normal earth gravity at sealevel. That
actually varies with latitude--in northern
Norway it is some 0.2 percent larger than
in southern France. Our standard acceleration
turns out to be strong, like what you'd expect
in northern Norway but the difference is not
too important.

THE WEIGHT OF UNIT MASS (pound mass, lb)
IN NORMAL GRAVITY (1 inch/tr^2 )
IS THE UNIT FORCE (pound force, pd).

This was the original motivation for setting up
pound-inch units, to have both the unit force
and the unit mass be the familiar pound.

In metric the unit mass is kilogram and the
unit force is newton. nobody likes to use
newtons and hardly anyone knows their weight
(which is a force) in newtons. The weight of
a kilogram in normal gravity is not equal to
a newton, instead it is 9.80665 newtons!
So pound-inch is better than metric here because
the weight of a pound mass is the pound force.

Also pound-inch is better because the speed of
light is exact and clean: 600 million inch/trice.
and because there is a concise exact Planck's h.

These concise definitions determine the sizes of
inch and pound and they make our inch 72 ppm
(7 thousandths of a percent) longer than the
old inch. This is a small barely perceptible
difference and doesn't matter for physics
coursework. The definitions also make the pound
mass 27 ppm (3 thousandths of a percent) larger
than the old pound mass, also no big deal.
For lab work you can keep on using
same inch rules and pound balance-weights if you
are lucky enough to own a set. Otherwise you
have to grunt around with grams and a calculator.
Anyway physics lab assistants you are advised
not to throw old inch and pound gear away because
this system is as decimal as metric and even
a bit cleaner. It should be included in freshman
and sophomore classes as an alternative system.
END OF QUOTE

So, Leonard, when the metric system is "fixed" in around 2010, will you then be in favour of the metric system/SI?

SI metric is irreparably bad in the sizes of its
units.

The answer is no.

there is no way metric could be fixed sufficiently
to make it a satisfactory purely decimal system.

I believe very strongly that there is room in the
world for three types of unit system.

1. non-decimal systems with ratios like 12, 36,
16 as well as 10, with sizes of units having
evolved through the trial and error of human use
so that the sizes are handy.

2. systems attempting to be purely decimal, such
as SI metric and various non-SI systems used
by scientists because they work better than SI
in certain applications, and also the pound-inch
system Andrew,Paul,and I have been trying out
(especially strong potential in introductory
college physics coursework I think)

3. A possible hybrid consisting of a purely decimal
core system like pound inch with non-decimal
auxilliary units (eg 12 inch, 36 inch) with
specially names adjoined to the core system.

Bryan I don't see how you could have gotten the
idea that I would consider SI satisfactory when
they redefine the kilogram. The units will still
be a bad size (the metric speed of light and the
metric Planck's h will still be very ugly numbers)
they will just be DEFINED better.

What I am always urging is that we get the jump on
metric and define pound-inch (this doesnt concern
you since it is a purely decimal system but that
is what I am discussing) based on exact values
of natural constants which is the trend in metric
but is an unfinished gradual trend. They use that
technique of definition for the meter but have
not yet adopted it for the kilogram. (There is still
a block of metal in Paris called Le Grand Kilo
that is the definition of the kilogram.)
But HOW YOU DEFINE is only one aspect. There is
also the SIZES OF THE UNITS and SI sizes were
chosen badly in 1790 which is something they cannot
fix.