Slashdot Mirror
US Objects To the Kilogram
Velcroman1 writes "For 130 years, the kilogram has weighed precisely one kilogram. Hasn't it? The US government isn't so sure. The precise weight of the kilogram is based on a platinum-iridium cylinder manufactured 130 years ago; it's kept in a vault in France at the International Bureau of Weights and Measures. Forty of the units were manufactured at the time, to standardize the measure of weight. But due to material degradation and the effects of quantum physics, the weight of those blocks has changed over time. That's right, the kilogram no longer weighs 1 kilogram, according to the National Institute of Standards and Technology. And it's time to move to a different standard anyway. A proposed revision would remove the final connection to that physical bit of matter, said Ambler Thompson, a NIST scientist involved in the international effort. 'We get rid of the last artifact.'"
Death to KILLograms!
Ounces and pounds were way a head of the time and are becoming even more useful with the advent of computer systems and the common use of base16.
16 ounces in a Pound is not just coincidence.
F=15 ounces
10 = a pound
We can all agree, I am sure, it's easier to look at 89 and go, 8 pounds 9 ounces. With metric I have to keep moving the decimal place around and remember how many 0s there were in huge words like kilogram, milligram, centigram.
Because this prototypical kilogram is what the definition of the pound is currently based on.
It clearly states this is an international effort, and the objection is not the the unit 'kilogram' but rather to using a decaying (however slowly) object as the reference mass.
Well, you can try counting atoms. But apparently that turns out to be a royal pain.
The World Wide Web is dying. Soon, we shall have only the Internet.
seriously, this is pretty old. physicists working in metrology have been working to redefine the kilogram for at least the last few decades
"For I am a Bear of Very Little Brain, and Long Words Bother Me"
We have American pints and British pints; the imperial tone, the short ton, and the tonne; why not have an American kilogram and traditional kilogram as well? That should really simplify things for NASA/EUA coordination.
It's the US of A -- we don't use the kilogram anyway. Change it as you like.
That being said, keep your filthy hands off my hogshead.
Blog,Twitter
Aren't they just proposing removing the dependence on the 1 kilogram cylinders?
From the article:
Physicists may scoff at the thought people allowed to walk among the living who don't know what a Planck value is. But all you need to know is, they're using it to determine the mass of one mole of silicon atoms.
From there on, they'll theoretically be able to deduce a perfect kilogram and it won't have anything to do with lumps of metal ever again. /quote
"There is one thing of which one can say neither that it is one metre long, nor that it is not one metre long, and that is the standard metre in Paris." - Wittgenstein, Philosophical Investigations
Nah, it's actually pretty easy. You say something like "one kilogram is the mass equivalent of the energy of 3.40812408 gazillion photons with a wavelength of 550.9466543 nanometers." The meter is already defined in terms of speed of light and the second, and the second is defined in terms of the natural frequency of the caesium-133 atom. So in the end, everything is defined in terms of the speed of light and the caesium atom, with no artifacts needed.
then how do you define a liter?
OH I JUST BLEW YOUR MIND
We're going to let the kilogram "float" and put it on the commodities market. It should triple the value of the gram
For justice, we must go to Don Corleone
I'm not even sure we even use Imperial units anymore...
From reading the news, I believe our units are:
- Hairs
- Stories
- Football Fields
- Libraries of Congress
Newton is a weight. The summary (and the Fox article) are incorrect, while the NIST article correctly refers to the reference mass.
MJC
and misses the point. The variability of the kilogram standard is a scientific and engineering concern, not a political one.
Wikipedia discusses the issue: http://en.wikipedia.org/wiki/Kilogram#Proposed_future_definitions
In a nutshell - in order to create 1 kilogram physical standard masses, you have to first know what a kilogram IS. The physical standards referred to in the article do not appear to have retained constant mass over time. You can't define a constant based on something that is variable, so the current masses are (as I understand it) acknowledged to be an inadequate basis for the definition of the unit. The problem arises when you try to pick something to define it with that is both stable (i.e. a fundamental property of the natural laws of the universe) and practical (can actually create one to use as a practical mass standard against which you can prepare working standards.)
From articles that have popped up about this over the years, my guess is they will have to pick something as a basis and then work on various practical techniques to get as close to that ideal as possible - the question is what specifically to pick. N Carbon atoms? N Si atoms? What are the pros and cons when trying to physically create something that represents those numbers? How stable will a standard created according to a chosen standard be over time? (I.e., how often to we have to make new master standards? It's an important question - obviously the existing masses were not chosen with the expectation that their mass would vary with time, so how do we know to trust a given solution?)
So it's not the US objecting to the kilogram as a unit, but rather concern over the methods used to DEFINE the unit. That's something quite rational, not specific to the USA, and of scientific interest. Editors, how about changing the title to "US to Propose New Method of Defining a Standard Kilogram" instead?
"I object to doing things that computers can do." -- Olin Shivers, lispers.org
Last I heard, nobody had come up with a way to define mass without referring to an artifact. It seems easy but they all turn out to be circular.
kilogram: the amount of mass required to deflect a proton by X degrees at a distance of Y meters.
I'm guessing X and/or Y would have to be quite small.
Ain't no such thing, or else something as basic as an electronic weigh scale wouldn't work. To rephrase: solid metals are compressible enough to measure the effect (strain) due to very reasonable external loads -- you'd think that liquids would be, too. And yes, they are.
Bulk modulus of steel, commonly strain gaged in weigh scales: ~160 GPa
Bulk modulus of water: ~2.2 GPa.
Water is on the order of 100 times more compressible than steel. Yet steel's and similar metals' compressibility (modulus) is routinely used in measurement applications!
Now to give you an idea of how compressible metals are: a soft iron sphere with a single strain gage bonded to it will give you, IIRC, 1m depth resolution if you hook it up to reasonable digital strain meter. I did the math once on Yahoo Answers somewhere, don't have the link handy.
Don't believe all they tell you in grade school for a lot of it is bullshit.
A successful API design takes a mixture of software design and pedagogy.
No. The reference electrons are specially-calibrated in the lab to meet the exacting standards of the measurements industry. If you start using sub-standard electrons, you get sub-standard measurements.
I have personally seen the effects of creating matter using electrons with a charge of -0.93 instead of the usual -1. The matter that we were shipping had a net positive charge, so we had to include EXTRA electrons in the order so that the USP guy what not fatally electrocuted when he picked up the box. Do you have any idea how much those extra electrons cost my company?
Please do not even get me started about cut-rate protons. What happens when heavy water is not quite so heavy? You don't even want to know.
"-1 Troll" is the apparently the same as "-1 I disagree with you."
The entire point of redefining the kilogram would be to allow any sufficiently-technical laboratory to make their own mass. Right now, there are forty artifacts that must be kept safe. If you do not have one of these artifacts, you in fact have no way to determine what your kilogram actually is. Hell, the artifacts probably do not even have the same mass as each other. So they are proposing to replace a few sets of metal with an instruction manual on how anyone with the right technology can make their own reference weight. That's a huge difference.
A NYC lawyer blogs. http://www.chuangblog.com/
Well, you can try counting atoms. But apparently that turns out to be a royal pain.
Or at least an Imperial pain. :)
http://en.wikipedia.org/wiki/Binding_energy#Mass_deficit
title of this slashdot article should be:
Le Kilogramme is to walk the Planck. :)
http://www.theregister.co.uk/2010/10/28/official_french_kilogramme_marked_for_the_bin/
root@127.0.0.1
Essentially a sphere will be created of a specific isotope of silicon and a specific diameter. This sphere will have a known number of atoms. This is superior not only because of degradation of a physical standard, but also because it will be easier to create a standard from basic principles using appropriate lab equipment.
The US is quite late in it's objection as the problem has been known and accepted for many years. TIme and distance is essentially measured with light, and only the kilogram still has a physical representation.
It is probably a simple matter for the US to accept the new standard.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
The point is that the definition needs to be practical. We need to have a way to actually measure a kilogram using the definition, so we can calibrate our scales. If we can not use the definition to calibrate a scale to some very high accuracy, it is useless.
The Avogadro project (the thing in your link) has been going on since 2007.
The NIST (the U.S. measurements standards body) provided an implementation of another possible solution to the problem in April of 2007.
To say that the U.S. is just now objecting is inaccurate.
To say that the U.S. is late in its objection ignores the fact that the U.S. has been working on the problem with international standards bodies for many years.
What (unsurprisingly) the Fox News article gets wrong is that the NIST is not submitting a formal objection.
The Consultative Committee for Units (one of the advisory groups for CIPM), of which the NIST is a member, has submitted a formal resolution to change the definition to the CIPM. The CIPM is about to submit that resolution to the CGPM, which is the international body that regulates these definitions.
Darth --
Nil Mortifi, Sine Lucre