The second technique is instead based on the Avogadro
constant, and involves counting a certain number of atoms of a

atomic mass.

I'm going to spend two month in a research centre, in Italy, where

trying to exactly calculate the distance between atoms in a Silicium
Crystal.
That should be part of the European project for finding the new

definition!

In article <HvwXd.108006$tl3.31158@attbi_s02>, Sam Wormley <swormley1@mchsi.com> writes:

Could you, please, explain how replacing the current definition with a
*less* precise one will *reduce* the uncertainties in anything. If,
indeed, the above mentioned scientists said this (a big if, since I
know how things get distorted in popular writeups) then they're
gibbering. Under no circumstances whatsoever does decrease in
precision produce an increase in precision.

For instance, the precision of certain electrical measurements, such as the
volt and ampere could be improved by a factor of 50.

A similar change was made in 1983, when the old definition of the metre
- the distance between two metal scratches on a platinum bar - was
withdrawn.

Yes, and in this case the old standard was replaces by a new, more
precise one.

One should, by all means, strive to base all units on fundamental
processes, not accidental artifacts. However, in no case should this
be done in a way that sacrifices accuracy. If obtaining the required
accuracy will take few more years, so be it.

In article <HvwXd.108006$tl3.31158@attbi_s02>, Sam Wormley <swormley1@mchsi.com> writes:

macromitch@internetCDS.com wrote:

Sorry Sam But,
Weight in gravity is limited.

Ref: http://physicsweb.org/articles/news/9/3/6/1
New look for the kilogram

8 March 2005

The current definition of the kilogram - that it is equal to the mass
of a piece of platinum-iridium alloy kept in a vault in Paris - is out
of date and should be abolished, according to physicists in the UK, US
and France. The researchers believe it is time instead to define the
kilogram in terms of fundamental constants, like the other six SI base
units. This is despite the fact that the proposed new definitions are
less precise than that based on the platinum-iridium "international
prototype".

Defining the kilogram in terms of the prototype - which is housed at
the Bureau International des Poids et Mesures - means that the value of
the kilogram changes if the mass of the prototype changes. This can
happen if, for example, the object collects dust from the atmosphere,
is cleaned or becomes damaged.

In contrast, the other six SI units are defined in terms of atomic or
fundamental constants. For example, the metre is defined as the
distance travelled by light in a vacuum in 1/299792458 of a second and
the second itself is defined as the duration of 9192631770 cycles of
the radiation emitted by a particular electronic transition in a
caesium-133 atom. These definitions allow researchers to make
measurements in SI units without the need for a single "master
standard".

Scientists have proposed two ways to redefine the unit of mass. The
first is based on the Planck constant and requires a 1-kilogram mass to
be supported against Earth\x{2019}s gravity using a precisely measured
magnetic force. The second technique is instead based on the Avogadro
constant, and involves counting a certain number of atoms of a specific
atomic mass. However, many believe that any new definition of the
kilogram should not come into force until it at least equals the
precision of the current definition - that is, 1 part in 108. So far,
neither method has achieved better than 1 part in 107.

But Ian Mills of the University of Reading in the UK and colleagues at
NIST in the US and the BIPM believe that the International Committee
for Weights and Measures (ICWM), which is responsible for ensuring that
units of measurement are uniform worldwide, should go ahead anyway and
adopt one of the new definitions when it next meets in October 2007
(Metrologia 42 71).

Redefining the kilogram now would have immediate advantages, such as
significantly reducing the uncertainties in the values of a large
number of other important fundamental constants that are intimately
related to the definition of the kilogram say the scientists.

Could you, please, explain how replacing the current definition with a
*less* precise one will *reduce* the uncertainties in anything. If,
indeed, the above mentioned scientists said this (a big if, since I
know how things get distorted in popular writeups) then they're
gibbering. Under no circumstances whatsoever does decrease in
precision produce an increase in precision.

For instance, the precision of certain electrical measurements, such as the
volt and ampere could be improved by a factor of 50.

A similar change was made in 1983, when the old definition of the metre
- the distance between two metal scratches on a platinum bar - was
withdrawn.

Yes, and in this case the old standard was replaces by a new, more
precise one.

One should, by all means, strive to base all units on fundamental
processes, not accidental artifacts. However, in no case should this
be done in a way that sacrifices accuracy. If obtaining the required
accuracy will take few more years, so be it.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

In article <HvwXd.108006$tl3.31158@attbi_s02>, Sam Wormley

macromitch@internetCDS.com wrote:

Redefining the kilogram now would have immediate advantages, such as
significantly reducing the uncertainties in the values of a large
number of other important fundamental constants that are intimately
related to the definition of the kilogram say the scientists.

Could you, please, explain how replacing the current definition with a
*less* precise one will *reduce* the uncertainties in anything. If,
indeed, the above mentioned scientists said this (a big if, since I
know how things get distorted in popular writeups) then they're
gibbering. Under no circumstances whatsoever does decrease in
precision produce an increase in precision.