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Experts Suggest Replacing Definition of Kilogram
fenimor writes "The kilogram is the only one of the seven basic units of the international measurement system defined by a physical artifact rather than a natural phenomenon. International team of scientists suggest replacing the kilogram artifact -- a cylinder of platinum-iridium alloy about the size of a plum --with a definition based on one of two unchanging natural phenomena, either a quantity of light or the mass of a fixed number of atoms. They propose to adopt either one of two definitions for the kilogram by selecting a specific value for either the Planck constant or the Avogadro number."
And this is news why? It obvivously makes sense to have the kilogram based on some universal constant as opposed to a block of metal sitting in some museum.
I thought one cc of water weighs one gram. Thus one litre of water weighs one kg. Am I wrong? This would certainly satisfy the criteria of natural phenomena vs. artifact, although I suppose that definition gets a trifle fuzzy when we start talking about measurements like picograms.
That would work fine, and I believe was the original definition. Unfortunately, pressure has a mass component, so your definition is circular.
I'm not sure how this slipped by in slashdot but this has nothing to do with the academic area of mathematics :-P
Sounds a lot more like science or physics to be specific.
C'mon people lets try to give things a realistic category. Anyway why the hell is math a subcategory of science??
Just my 2 kilos, flame me if you like.
Why the motivation for the change? The mass of subatomic particles have been given in kg for over a century. What exactly needs a more precisely reference of measurement? Physicists use their own units when it's convenient anyway. . . .
When things get complex, multiply by the complex conjugate.
You'd lose mass instead.
"[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz
I was going to be nice to you up until this sentence - if you want to suggest that someone is stupid, can you at least be sure that you're not wrong? Many posts have replied with the appropriate info (not to mention that you *did* pass grade school, did you not - if so, how can you *not* know that the gram is defined in terms of the kilogram?)
In any case, is this just typical Wes Janson stupidity?
So a change in the kilogram automatically affects the pound.
However, when they do make this change, it will not be a "modded" kilogram. It will be the same mass as before; it's just that it will be possible (ultimately) to measure it much more precisly and time-invariantly (as the standard is losing mass over time).
The only countries left that don't use metric are America and Bhutan. Bhutan is a fundamentalist islamic country that doesn't even have any phones yet. I guess we can see what the American technical level is.
As opposed to what people seem to be suggesting, I don't think they are trying to replace kilogram with a brand-new unit, but just changing the definition. You would still say the brick is 1Kg; however, that will no longer mean that your brick is equivalent to the platinum-iridium cylinder, but a constant as defined by a unchanging natural phenomenon as suggested by the scientists...
To iterate is human; to recurse, divine!
Now, I know those definitions are techincally correct, but who thinks these ideas are easily applicable? I mean, the point of having a definition is to be able to calibrate everything else, right? So how on earth is a watch manufacturer or repair person going to say "alright, the cesium atom vibrated 9,192,631,769... 9,192,631,770 times. That's a second."
Is there actually a method of directly using these definitions?
-Dizzle
"I most likely AM so interested in myself."
This actually came up in my high school physics class a few years back. Since then, I've given it some thought, and my best guess was to define a kilogram in terms of the deflection of a beam of light under the influence of gravity over a given distance. In other words, define it in terms of the deflect of a beam of light passing a kilogram point charge at a certain distance.
To make laws that man cannot, and will not obey, serves to bring all law into contempt.
--E.C. Stanton
The metric system was the most fundamentally correct system of measurement ever concieved by man, beast or God.
;).
You'd certainly think that reading all the hype on this bbs.
Remeber this article the next time a English/metric debate comes about. There is nothing inherently better about either system. That argument being nullified, should we switch based on the rest of the world? That is the only valid argument.
Don't start your argument, thought process, or comment with the mistaken common wisdom of "Everyone knows metric is better...."
And while I am ranting, but not quite as obvious, I don't want to hear 'I know what a kilometer is, I don't know what a mile is...' If you can pace off one, you can pace off the other. You certainly don't have an inborn sense of what a kilometer is anymore than you have an inborn sense of the mass of a plum sized chunk of some alloy.
Neither system is anymore natural than the other, get off your high horse and make a rational comment (unlike this rant
Someone smart famous once said "Any technology, sufficiently advanced, is indistinguishable from magic." These fundamental definitions are following the same path. Superbly and unarguably accurate, but also completely incomprehensable for anyone that doesn't have half a million dollars worth of sophisticated technology.
Always going forward, 'cause we can't find reverse.
They set it equal to 1 pound
There are two common systems of units, mks ... and cgs ... . The mks system is now more often referred to as the SI. ... In any case, what you're referring to is utterly trivial and/or irrelevant ...
To a scientist or engineer it is trivial, however to a (European) cop, or to someone buying butter it is not so trivial. Reporting the perp's weight in grams would not be sound practice. For everyday use the base unit needs to be visualisable/imaginable on a human scale.
Half a kilo of butter, or a pound of butter is a reasonable purchase. Grams just don't cut it. What am I getting if I ask for 80 grams of salami? Well I guess I can visualize it and some Europeans buy it that way, but the average everyday user of a measuring system is nearly innumerate. They want to buy one or two or maybe a half of something.
One of the nice things about the British system of measurement (which pretty nearly only the Americans use officially, though with a few changes) is that the units are exactly the sort of thing you often want about one of. A pint of beer, a gallon of kerosene, a bale of hay, a pint of milk if you live alone or a quart or a gallon depending on the size of your family, half an acre of land, etc. (yes, yes, I don't think a bale is an Imperial measurement).
The metric equivalents never seem to be just right, but we'll just have to live with them
In wartime... truth is so precious that she should always be attended by a bodyguard of lies. (Churchill)
To a scientist or engineer it is trivial, however to a (European) cop, or to someone buying butter it is not so trivial.
The topic of the article is only relevant to scientists -- to a very, very small set of scientists who do certain types of high-precision work. The redefinition of the kilogram they're talking about would be utterly inconsequential to everybody else.
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Half a kilo of butter, or a pound of butter is a reasonable purchase. Grams just don't cut it.
You can still use kilos... using grams as the base unit does not completely eliminate kilos from the face of the earth.
What am I getting if I ask for 80 grams of salami? Well I guess I can visualize it and some Europeans buy it that way, but the average everyday user of a measuring system is nearly innumerate. They want to buy one or two or maybe a half of something.
Uh... if you need to buy eighty grams, then you'd have to say something like 2/25ths of a kilo. It's actually easier to use grams in that example. Also, if you ever need eighty grams of salami, you could just ask for one medium-thickness slice. Thus, we should use the slice of salami as a SI unit rather than the gram or the kilo. Wait, that wouldn't work...
'The moon wieghs the same as thirty-two billion slices of salami...'
Well, whatever. I say we just use them interchangeably.
To a scientist or engineer it is trivial, however to a (European) cop, or to someone buying butter it is not so trivial. Reporting the perp's weight in grams would not be sound practice. For everyday use the base unit needs to be visualisable/imaginable on a human scale.
Half a kilo of butter, or a pound of butter is a reasonable purchase. Grams just don't cut it. What am I getting if I ask for 80 grams of salami? Well I guess I can visualize it and some Europeans buy it that way, but the average everyday user of a measuring system is nearly innumerate. They want to buy one or two or maybe a half of something.
Do you think European cops say "I'm in pursuit, west bound on Main, at 33m/s"? Or do you think they might stuff using base units and say 120km/h?
Do you really say things like "It's a 100000m drive" and "I'll meet you there in 2700 seconds"?
Well, your watch manufacturer is simply producing watches for the public. To an individual person it really doesn't matter if they are ahead or behind in their day by 15 or 20 seconds ... maybe even +/- 5 or 10 minutes. So to them, a watch that can hold time to within 5 or 10 seconds over the course of a month or so is just fine. I'm not sure how accurate a quartz watch can get, maybe it's even more like 5 or 10 seconds over a year or so?
Anyways, it's one thing for a watch manufacturer to achieve a certain accuracy. It's another thing when you are trying to transfer a satellite from high earth orbit into an elliptical sun orbit to intersect neptune or a KBO. The accuracy requirements for making certain burns to change trajectory, or making a control movement of the momentum wheels is another thing. Or in a particle accelerator, when to activate certain portions of the cyclotron, etc.
These definitions are for the purposes of science and technology. A company can offer a service where they dumb down the definition for the public.
The whole reason we (countries that use rational measurement systems)have standard prefixes is that we can use appropriate units and avoud huge integers or fractions in common usage. I don't know why you think this is difficult. Would you prefer to be using pounds, shillings and pennies instead of dollars and cents -- that was one reform the US did before most other countries. So do you say "80 cents" or "eight-tenths of a dollar" (or 16 shillings)? And unless you're buying in bulk, most food is bought in quantites (or units) less than a pound, let alone a kilo. That's why you use ounces, by the way. Three ounces is about 80 gm. At the deli, most food here is labelled as price/100gm (cheese, ham, etc); a the butcher and green grocer it's mostly by the kilo. It makes things a lot simpler to just multiply weight in kilos by price in dollars/kilo.
The metric equivalents never seem to be just right, but we'll just have to live with them
After a few months you adjust. Australia went metric when I was at primary school.
It pretty much depends on what you understand under "infinite" ;)
Given the fact that you are in bound by the laws of physics which state that on a certain (very low) level you have a certain uncertainty (sic) when you reach into "quantum level", one could argue that, in fact, 0.1111111...1111[something] for as many times you can until you hit that treshold times 9 does indeed NOT equal 1.
By reading this signature you agree to not disagree with the post you just read.
That's like asking how many pounds in a foot... Rhode Islands are units of size and Libraries of Congress are units of data. Elephants are units of mass...
=Smidge=
So why do you call your superior system "base-12" as in "base-(1*10^1+2*10^0)"? Here's why: Because base-12 masochists enjoy mixing base-10 numbers with base-12 units.
The definition was originally that a kilogram was the mass of one litre of pure water at 4 degrees Celsius and standard athmospheric pressure, but that is a circular definition, as the definitions of the SI units for pressure depends on mass.
As a result a kilogram is now the mass of the kilogram artefact - if the artefacts changes mass, it still remains 1 kilogram