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Kilogram Conflict Resolved At Last (nature.com)
An anonymous reader writes: As the capabilities of science and engineering expand, they rely more on the precision of measurements. It's vitally important, then, to make sure the standard units underpinning those measurements don't change. This is a problem for the kilogram. For years, it has remained the only SI unit based on a physical object — a small cylinder of platinum and iridium. Scientists have been arguing about how to replace it for decades, but now it looks like their efforts are finally reaching fruition. They finally have all the data they need to define the kilogram with mathematical constants, which solves the problem of the variability of physical objects. "One method, pioneered by an international team known as the Avogadro Project, involves counting the atoms in two silicon-28 spheres that each weigh the same as the reference kilogram. This allows them to calculate a value for Avogadro's constant, which the researchers convert into a value for Planck's constant. Another method uses a device called a watt balance to produce a value for Planck's constant by weighing a test mass calibrated according to the reference kilogram against an eletromagnetic force." Further research has narrowed down the value of Planck's constant, and experimental data from standards bodies is finally matching up. "If they are proved right, in 2018, Le Grand K will join the meter as a museum piece."
You're not going to win this one. From the nice Wikipedia article concerning the definition of a foot:
Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly. In both systems, the foot comprises 12 inches and three feet compose a yard.
It's cylinders all the way down.
Faster! Faster! Faster would be better!
The metric zealots get mad at me for pointing out the points of weakness of the metric system. Here is one I forgot about. Their length unit is based on a physical cylinder of metal. Although it makes sense, since the original design spec apparently was "Make it a little longer than a yard, just to piss of those English bastards."
Perhaps your memory is failing you again..? A metre is defined as the distance light travels in 1/299792458 of a second. Originally, I believe in the 18th century, this was intended to be one ten-millionth of the distance from the pole to the equator. The former is obviously a better definition because Earth is not perfectly spherical.
In any case... Using the term 'metric zealot', apparently un-ironically, right out of the gate - doesn't do your credibility any favours (or it's a deliberate troll; in which case - well done).
If you're a genuine 'imperial zealot' then what, out of interest, is your best pro-imperial argument? I'm curious because as far as I can tell, imperial is shit. And I say that as someone who has had to deal with both systems.
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.
Their length unit is based on a physical cylinder of metal.
Nope, it's based on the speed of light in a vacuum. You are thinking of the unit of weight.
Anyway, how is that stupid? The imperial version, the pound, is based on a physical quantity as well because it is officially defined as 0.45359237kg. In fact most (all?) imperial measures are defined as precise metric values now, so any criticism you have of metric standards apply equally to imperial ones.
Metric is far superior. You get easy decimal maths, easy conversions, SI units of magnitude and naming conventions. If you want to use base 12 for the nice divisions, you can use base 12. The only reason to stick with imperial measures is familiarity and legacy stuff.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
Apparently more stable than a block of something which sheds some matter over time, yes.
So, your choices are: 1) measure according to a physical object which can change over time, or 2) measure according to a known set of physical properties which can be reproduced.
And there's nothing to say over time as the science gets better they don't tweak this.
But, in terms of defining in terms of a measure someone can reproduce, it's gotta be better than "1kg is this artifact we made".
I mean, this is what we have now:
So, it's gotta be more stable than an artifact.
Lost at C:>. Found at C.
Well the full story of the meter is:
1. let's make something around 1 yard in length based on the Earth
2. choose one ten-millionth of the distance from the pole to the equator
3. define as the distance between two marks on a chunk of metal
4. define as the distance light travels in 1/299792458 of a second
He brought up 1 and 3. You brought up 2 and 4 but that doesn't mean he's wrong. All 4 points are correct.
The US system of measurement (1) and the metric system approach the problem from two completely different viewpoints.
In the US system the goal is to make dealing with the physical objects easy -- to get from one size to the next larger one most of the time you double something. To get to one size to the next smaller one most of the time you halve it. Mathematically this makes things a bit tougher when doing calculations. The naming system unfortunately requires you to remember different names for each unit.
In the metric systems the goal is to make the mathematics easy (and also the naming system). In this system to go from one size to the next you simply shift where the decimal point is located. However, dealing with the physical objects is actually much tougher. To go from one meter to one centimeter you need to cut the length into 100 equally sized pieces...this is hard!
(1) It turns out that both systems were originally French...the original name of the US system is the avoir du pois system (goods by weight).
Through Paris.
The metre was officially defined as 1/10,000,000th the straight line distance between the North Pole and the Equator, through Paris, France.
It's why everything's in French (why the official term for "metric" is SI, or Systeme Internationale... French!).
Anyhow, the kilogram is the only unit of measure still based on a physical object, something they've been trying to change for decades now. The importance of this is if you can derive all the fundamental units of measure from physical constants, then it becomes a universal system of measurement.
And the reference kilogram has been losing weight, which means all of us have steadily started weighing more and more as time goes on.
If that were true, it'd be nice. But, no, I have to figure fractions of inches, 12 inches to the foot, 3 feet to the yard, and 1760 yards to the mile. Not to mention that the US survey foot is different than the standard foot in some states and not in others. And pressures get measured in pounds per square foot, pounds per square inch, feet of water, inches of water, inches of mercury, atmospheres, etc., none of which relate by multiples of two. And a gallon is the volume of a cylinder 6 inches high by 7 inches in diameter if you assume pi to be exactly 22/7 - no factors of 2 between cubic feet and gallons. Don't even get me started about viscosity, where we have wonderful measures like Saybolt Seconds Universal, which doesn't even relate linearly to the standard measures that you need if you're doing any calculations. (ASTM had to issue a standard - ASTM-D-2161 - for converting between useful measures of viscosity and SSU or SFU in order to minimize discrepancies between measures.)
The good thing about SI units is that they're mostly consistent. No need to convert pounds to slugs and miles per hour to feet per second before plugging the numbers into the formula. Fundamental measures relate directly to derived quantities.