From: Eliezer S. Yudkowsky (sentience@pobox.com)
Date: Sun Dec 07 2003 - 16:33:45 MST
While reviewing 2003, I ran across this article, which describes
humanity's creation of yet another Artifact like the Clock of the Long
Now. The key point is highlighted in the article's body for your convenience.
"It's probably the roundest item ever made by hand. 'If the earth were
this round, Mount Everest would be four meters tall,' Dr. Nicolaus said.
An intriguing characteristic of this smooth ball is that there is no way
to tell whether it is spinning or at rest. Only if a grain of dust lands
on the surface is there something for the eye to track."
Whatever would an alien species make of the Silicon Sphere, I wonder?
Would they ever guess its purely philosophical purpose?
A cheering sign that humanity is still progressing toward becoming an
Incomprehensible Elder Species.
*****
Scientists Struggling to Make the Kilogram Right Again
NYT May 27, 2003
By OTTO POHL
BRAUNSCHWEIG, Germany - In these girth-conscious times,
even weight itself has weight issues. The kilogram is
getting lighter, scientists say, sowing potential confusion
over a range of scientific endeavor.
The kilogram is defined by a platinum-iridium cylinder,
cast in England in 1889. No one knows why it is shedding
weight, at least in comparison with other reference
weights, but the change has spurred an international search
for a more stable definition.
"It's certainly not helpful to have a standard that keeps
changing," says Peter Becker, a scientist at the Federal
Standards Laboratory here, an institution of 1,500
scientists dedicated entirely to improving the ability to
measure things precisely.
Even the apparent change of 50 micrograms in the kilogram -
less than the weight of a grain of salt - is enough to
distort careful scientific calculations.
Dr. Becker is leading a team of international researchers
seeking to redefine the kilogram as a number of atoms of a
selected element. Other scientists, including researchers
at the National Institute of Standards and Technology in
Washington, are developing a competing technology to define
the kilogram using a complex mechanism known as the watt
balance.
The final recommendation will be made by the International
Committee on Weights and Measures, a body created by
international treaty in 1875. The agency guards the
international reference kilogram and keeps it in a heavily
guarded safe in a château outside Paris. It is visited once
a year, under heavy security, by the only three people to
have keys to the safe. The weight change has been noted on
the occasions it has been removed for measurement.
"It's part ceremony and part obligation," Dr. Richard
Davis, head of the mass section at the research arm of the
international committee.
"You'd have to amend the treaty if you didn't do it this
way."
That ceremony has become a little sorrowful as the guest of
honor appears to be, on a microscopic level at least,
wasting away.
The race is already well under way to determine a new
standard, although at a measured pace, since creating
reliable measurements is such painstaking work.
The kilogram is the only one of the seven base units of
measurement that still retain its 19th-century definition.
Over the years, scientists have redefined units like the
meter (first based on the earth's circumference) and the
second (conceived as a fraction of a day). The meter is now
the distance light travels in one-299,792,458th of a
second, and a second is the time it takes for a cesium atom
to vibrate 9,192,631,770 times. Each can be measured with
remarkable precision, and, equally important, can be
reproduced anywhere.
The kilogram was conceived to be the mass of a liter of
water, but accurately measuring a liter of water proved to
be very difficult. Instead, an English goldsmith was hired
to make a platinum-iridium cylinder that would be used to
define the kilogram.
One reason the kilogram has lagged behind the other units
is that there has been no immediate practical benefit to
increasing its precision. Nonetheless, the drift in the
kilogram's weight carries over to other measurements. The
volt, for example, is defined in terms of the kilogram, so
a stable kilogram definition will allow the volt to be tied
more closely to the base units of measure.
A total of 80 copies of the reference kilogram have been
created and distributed to signatories of the metric
treaty. The sometimes colorful history of these small metal
cylinders underscores how long the world has used the same
definition of the kilogram.
Some of the metal plugs were issued to countries that later
vanished, including Serbia and the Dutch East Indies. The
Japanese had to surrender theirs after World War II.
Germany has acquired several weights, including the one
issued to Bavaria in 1889 and the one that belonged to East
Germany.
> To update the kilogram, Germany is working with scientists
> from countries including Australia, Italy and Japan to
> produce a perfectly round one-kilogram silicon crystal. The
> idea is that by knowing exactly what atoms are in the
> crystal, how far apart they are and the size of the ball,
> the number of atoms in the ball can be calculated. That
> number then becomes the definition of a kilogram.
>
> To separate the three isotopes of silicon, Dr. Becker and
> his team are turning to old nuclear weapons factories from
> the Soviet Union, where centrifuges once used to produce
> highly enriched uranium are able to produce the required
> purity of silicon.
>
> "We need so many nines," Dr. Becker said, and Soviet
> uranium processors are one of the only places to get them.
> "With the Russians, we're getting about four of them," or
> 99.99 percent pure silicon 28.
>
> A test crystal has already been produced, and Dr. Arnold
> Nicolaus, another scientist at the German standards
> laboratory, is responsible for measuring whether it is
> perfectly round. He has measured the crystal in a
> half-million places to determine its shape.
>
> It's probably the roundest item ever made by hand. "If the
> earth were this round, Mount Everest would be four meters
> tall," Dr. Nicolaus said. An intriguing characteristic of
> this smooth ball is that there is no way to tell whether it
> is spinning or at rest. Only if a grain of dust lands on
> the surface is there something for the eye to track.
Scientists from the United States, England, France and
Switzerland say the challenge of calculating the precise
number of atoms in a silicon crystal is too imprecise with
today's technology so they are refining a technique to
calculate the kilogram using voltage.
"Measuring energy is easier than counting atoms," said Dr.
Richard Steiner, a scientist at the National Institute of
Standards and Technology in Washington, who is leading the
international project to create the watt scale.
In the last few weeks, he has reported that his experiments
have yielded data that are close to what they need. "Now
we're into the picayune, itsy-bitsy errors," he said,
having recently corrected "totally ridiculous" errors of
100 parts per million.
The idea of the watt balance is to measure the
electromagnetic force needed to balance a reference
kilogram. As long as the gravitational field is precisely
known for the location of the experiment, the mass on the
scale can be related to power. (The gravitational field is
a complicated calculation that needs among other things
constantly updated changes in tidal forces.)
The definition of the kilogram would then be a measurement
of that power or in terms of something that could be
derived from it, like the mass of an electron. The
experiment in Washington is occurring in a large
three-story structure, but in spite of the complexity and
circuitous route of calculating mass, Dr. Steiner says he
is confident that his team will have persuasive data
shortly.
"In the short term, I think we'll win," he said.
Dr. Davis, who is working closely with those making the final
decision about the fate of the kilogram, says he is not so
sure. "In terms of published results, the watt balance is
closer of the two," he said. "But it's very hard to say
which is better."
Many scientists believe that the most elegant way to define
the kilogram is by counting out a kilo's worth of atoms of
an element. A project is under way to test that with gold
atoms. But the sheer number of atoms in a kilogram, a
number with roughly 25 digits in it, makes that approach
unfeasible for the foreseeable future.
For now, Dr. Davis is willing to set his sights lower in
the error-prone world of superprecision measurements. "It
would be nice," he said, "just to have two experiments in
the world that agreed with each other."
http://www.nytimes.com/2003/05/27/science/27KILO.html
*****
-- Eliezer S. Yudkowsky http://intelligence.org/ Research Fellow, Singularity Institute for Artificial Intelligence
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