Experts Suggest Replacing Definition of Kilogram 844
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."
I suggest (Score:5, Funny)
Re:I suggest (Score:5, Interesting)
Actually, if they happend to re-define it based on Avogadro's number, they might as well just say the GRAM is the new "basic unit" and the kilogram is just 10^3 grams.
Why ?
Because Avogadro's number is JUST an artifact of the definition of the (kilo)gram, not a fundamental constant - it's (been originally) defined as the number of atoms in 12 grams (or, whatever, 0.012 kilogram) of Carbon-12.
Talk about circular references then...
Now, basing the definition of the kilogram (might I suggest they also change that basic to gram instead of kilogram... please) on Planck's constant somehow would be a MUCH better ideea. However, the value of that constant [i.e. 6.6260693111111 * 10^-34 and so on] makes it pretty wierd to work with unless you multiply it with 9 [to get exactly 5.96346238 * 10^-33 which makes more sense somehow]. And even then it won't satisfy some people, as I'll bet you'll hear that 0.111111 and so on *9 does not equal 1
Not only that, but Planck's costant was ALSO measured "accurately" using the kilogram unit as reference.
Ok, this actually does give me a headache.
Re:I suggest (Score:5, Informative)
There are two common systems of units, mks (meter-kilogam-second) and cgs (centimeter-gram-second). The mks system is now more often referred to as the SI. In the cgs system, the gram is a base unit. In any case, what you're referring to is utterly trivial and/or irrelevant when it comes to the real work of defining the units. Any definition of the gram suffices to define the kilogram, and vice-versa.
Because Avogadro's number is JUST an artifact of the definition of the (kilo)gram, not a fundamental constant - it's (been originally) defined as the number of atoms in 12 grams (or, whatever, 0.012 kilogram) of Carbon-12.
It's happened before that they've changed things around so that something different was considered to be the more fundamental quantity: the speed of light used to be a measured quantity, but now it has a defined value. The whole issue is that as techniques change, you want to base your system of units on the things that can be most accurately measured (and reproduced) with the latest techniques.
Now, basing the definition of the kilogram (might I suggest they also change that basic to gram instead of kilogram... please) on Planck's constant somehow would be a MUCH better ideea. However, the value of that constant [i.e. 6.6260693111111 * 10^-34 and so on] makes it pretty wierd to work with unless you multiply it with 9 [to get exactly 5.96346238 * 10^-33 which makes more sense somehow].
I'm not sure where the <joke> tags belong here. Anyhow, giving h a defined value would be very much like the step they took when they gave c a defined value -- they did it because when techniques changed to the point where c was one of the most accurately measurable things in nature.
Re:I suggest (Score:5, Funny)
After all, an ounce of prevention is worth a pound of cure.
hawk
Re:I suggest (Score:5, Funny)
I'm sorry, I don't understand. Could you rephrase that in terms of Avagrado's number, please?
Re:I suggest (Score:3, Insightful)
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.
Re:I suggest (Score:5, Insightful)
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"?
Re:I suggest (Score:3, Funny)
-Graham
Technicalities of mass measurement (Score:3, Informative)
The main reason for platinum-iridium is that it's got a very low thermal expansion coefficient. Basically, it doesn't expand or contract much with change of temperature. However, densisty is also important. Don't ever ask a metrologist that old chestnut about which is heavier, a kilogram of lead or a kilogram of
Re:I suggest (Score:5, Informative)
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
But thats true for the metric system as well
In german we have "pound" as well, which is just slightly bigger than yours. And ppl in shops still buy "half a pound" of meat or something.
Same for land, we have an "ar" and a "hectar" which is obviously 100 ar, and we have a "morgen" wich is 25 ar and the typical size of a field in older times.
A ar is similar big as an acre (IIRC).
Same for drinks, who cares about your pint? Do you really think we order 350ml Beer?
We order a glass of beer, obviously. And depending on beer brand it is served in a typical size.
The sizes are: 0.2l for Kölsch and Alt. 0.3l for some kins of "Pils" which consider themslelf noble. 0.4 for a standard everywhere pils,a nd your pint is just between 0.3 and 0.4. The enxt size is 0.5l for Weiten.
The same applies for nearly any metric size, no one is buying xyz litres or something except he buys 40l gasoline for his car.
Bottom line we have as many "human" metrics as you but sine the metric system is in use they got rounded to the next best number.
angel'o'sphere
Just a few corrections (Score:3, Informative)
Re:I suggest (Score:5, Funny)
You buy beer by the .2L??? Germany is a nation of girly-men!
Re:I suggest (Score:3, Informative)
Re:I suggest (Score:3, Interesting)
Similarly, the common size of a land plot is "shest sotok" (six hundreds), meaning, of course, 600 square metres. And most people see
Re:I suggest (Score:3, Insightful)
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 fraction
Re:I suggest (Score:3, Funny)
Lunch?
Re:I suggest (Score:4, Funny)
Any fool can see what faction of an acre is a rectangle bounded by a furlong and a chain, or measure speed intuitively in millifurlongs per microfortnigt. This metric system is just unintuitive.
I know just how many furlngs per firkin my car gets, what the heck is that in litres per meter?
Re:I suggest (Score:3, Funny)
Do you think the new constant will retain the name, or will it be "The New Scientist Constant Relating Atoms to Grams brought to you by BASF, the Chemical Company"?
By the way (Score:5, Funny)
How many Avogadroes are in guaca-mole?
I guess 6.02x10^23...
Re:Earth Theory! (Score:3, Interesting)
Still, the intuitiveness of it is nice.
Re:I suggest (Score:3, Insightful)
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.
Re:I suggest (Score:3, Funny)
I wonder... (Score:4, Funny)
Re:I wonder... (Score:5, Funny)
Re:I wonder... (Score:5, Informative)
Re:I wonder... (Score:5, Funny)
Re:I wonder... (Score:3, Funny)
That's easy....
Formerly 1Kg.....
Re:I wonder... (Score:5, Funny)
Re:I wonder... (Score:4, Funny)
Re:I wonder... (Score:5, Informative)
does this mean (Score:5, Funny)
Nope, sorry (Score:5, Insightful)
Re:Nope, sorry (Score:4, Insightful)
How about ... (Score:3, Interesting)
Pressure (Score:5, Insightful)
Re:How about ... (Score:5, Interesting)
"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."
and a metre is defines as:
The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.
Unfortunately, there hasn't been a good way to count the number of atoms with any kind of precision, so that has precluded a good definition of the kilogram so far. Maybe now the physicists can actually count atoms accurately enough.
One could define it as the mass of some number of H2O molecules, but maybe its easier a measure a quantity of light or to count some larger atoms.
Re:How about ... (Score:3, Insightful)
Is there actually a method of directly using these definitions?
Mod Parent Up (Score:3, Insightful)
It works in a hierarchy (Score:5, Informative)
Where you actually need to use them directly, sure.
To give a real world example of how the standards work in practice... I used to write software for a company in the metrology (high precision measurement) business. They made machines that are used, for example, in quality control at the end of production lines. The gauges on the most popular machines gave accurate readings with resolutions of say 1-10m.
Those machines were calibrated from reference artifacts. These were themselves checked for accuracy on still higher precision equipment. (How they actually manufacture something so close to physical perfection is an interesting area in itself...)
Ultimately, there were white room areas with very careful decontamination procedures in place that were used almost exclusively for calibrating the company's most precise equipment and checking their reference artifacts.
From there, you were one step removed from the national standards laboratories. At that level the formal scientific definitions are just fine.
In other words, you work from major standards labs that can use the precise definitions effectively, and propagate the information (with some less, but little enough to be acceptable for the application in question) to more widely distributed testing facilities. A more trendy application of the same basic idea is the use of Internet-based real time clock services.
Grrr... Slashdot filtering... (Score:3, Informative)
Looks like we lost a mu in there somewhere: the resolutions for the popular machines were around 1-10 micrometres.
Re:How about ... (Score:3, Insightful)
Anyways, it's one thing for a watch manufacturer to achieve a certain
Just remember that they replaced the meter (Score:5, Interesting)
As technology to measure substances to great precision increases, its about time the kilogram got a redefinition as well, one not based on a single object.
Re:How about ... (Score:4, Interesting)
Adenosine triphosphate doesn't have much bearing on the mass of a quantity of water, even though it does provide biochemical energy to the physicists who're measuring it.
Just wait. (Score:5, Funny)
Re:Just wait. (Score:5, Funny)
Re:Just wait. (Score:3, Informative)
Also, we were the only ones sane enough to base our unit of volume/capacity on the cube of our linear standard (1 gal US = 231 in^3, as it's been since the 1800's or so). Both the British gallon and the SI liter both had ugly/cumbe
Re:Just wait. (Score:3, Funny)
We've been trying to tell you young upstarts the same thing ever since you forgot how to use the letter "u". :-)
Re:Just wait. (Score:3, Interesting)
However some mean a specific form of english, and in this particular conext (how well Americans speak it) they're often refering to how closely to the english of the time when Europeans, especially British, first settled the americas in the 1500-1600's. In that case it's my understanding the honors go to a subsection of America (or at least
Re:Just wait. (Score:3, Informative)
Bhutan is a devout BUDDHIST country, you hoser. And they have TVs now, although when I first read about that (more than 5 years ago), the Bhutanese were quite reasonably shy about appearing on it. Hence they had to cajole some poor sod to read the national news in a pained monologue. If you see some of the recent Bhutanese movies, though, it appears things are changing fast. I have no idea how they weigh their TVs and Buddhas, though.
On topic, I think it's great that they're using Avocado's Number t
that does it (Score:5, Funny)
And in other news... (Score:5, Funny)
Re:And in other news... (Score:4, Funny)
*Gasp from scientific community and silence*
<Frink> Sorry it had to come to that people.
Re:And in other news... (Score:4, Funny)
Re:Mmm... 4? (Score:3, Funny)
My favorite is apple.
The last time this was mentioned (Score:4, Informative)
You might find some additional background information about this effort in an earlier Slashdot article about this topic [slashdot.org], posted in May 2003.
How about (Score:2)
Re:How about (Score:5, Informative)
Redundant definition? (Score:3, Insightful)
Re:Redundant definition? (Score:3, Insightful)
Re:Redundant definition? (Score:3, Informative)
See NIST Special Publication 811 (1995 ed.), _Guide for the Use of the International System of Units (SI)_ by Barry N. Taylor (NIST is the National Institute of Standards and Technology, the successor agency to the National Bureau of Standards):
In commercial and everyday use, and espec
Re:Redundant definition? (Score:5, Funny)
I had been wondering if NIST was just pulling these so-called standards from their ass. I am glad you confirmed it. From now on, a kilo is the amount of coke a mexican hooker can snort in one week. Or course, that is under STP.
Re:Redundant definition? (Score:4, Funny)
Won't work, your refference subject is going to be far higher than sea level.
-
Hmm... (Score:4, Interesting)
Re:Hmm... (Score:3, Informative)
Huh? The units of Planck's constant are energy times time (eg., J s).
Re:Hmm... (Score:3, Informative)
No. Planck's constant gives the amount of energy carried by (and hence gives a meaning to the momentum of) a photon of a certain frequency. Its units are Joule-seconds, which is not a unit of energy. Since the frequency of a photon can be arbitrarily low, so can its energy.
Picture of the Kilogram Prototype (Score:5, Interesting)
http://www1.bipm.org/utils/common/img/mass/protot
Re:Picture of the Kilogram Prototype (Score:5, Interesting)
Re:Picture of the Kilogram Prototype (Score:5, Informative)
This is the definition of the kilogram. A kilogram is not 1L of H2O at STP (as mentioned elsewhere, pressure depends on mass), it's this little lump of metal. Changes in the mass of it are extraordinarily bad. They make copies of it for reference purposes, and then check the copies agains the original every 10 years. If there's a disagreement, the copy gets adjusted, not the original. The reference lump has actually lost about 50 micrograms in the last 100 years (and no one knows why). That's a lot (well, speaking at the level that micrograms get used at... 1 microgram = 0.000000001 kg), and the really highlights the need for an immutable reference point.
Readers may find the pertinent Wikipedia article [wikipedia.org] interesting.
Re:Picture of the Kilogram Prototype (Score:3, Interesting)
There is an international effort to come up with a new standard extremely precise silicon spheres - the cool thing about them is it is apparently impossible to tell if it is stationary or spinning unless you have a reference point on the surface (e.g. a speck of dust.)
Re:Picture of the Kilogram Prototype (Score:3, Informative)
It's nested in several jars for redundancy.
Chip H.
Obligatory Simpsons Metric Quote (Score:5, Funny)
Lisa: Principal Skinner, how's your transportation project coming?
Skinner: Not only are the trains now running on time, they're running on metric time! Remember this time people, 80 past 2 on April 47th. It's the dawn of a new enlightenment!
Re:Obligatory Simpsons Metric Quote (Score:3, Interesting)
Attempts of a JavaScript clock are here [bazzle.co.uk] if anyone is interested.
Re:Obligatory Simpsons Metric Quote (Score:3, Informative)
"or the mass of a fixed number of atoms" (Score:3, Insightful)
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. . . .
Re:"or the mass of a fixed number of atoms" (Score:3, Insightful)
Why use its known mass, of course! Then divide by 0.198078 (if it were pure platinum)/6.022E23 and take the nearest integer.
It doesn't really matter that there might plausibly be more or less atoms. Just find a number, suitably truncate it, and declare all subsequent decimal places to be zeros.
Isn't this exactly what happe
Bah (Score:3, Funny)
A little offtopic but still revelant
Finally... (Score:3, Funny)
Speed of light changes (Score:3, Interesting)
Meh ... how 'bout (Score:3, Funny)
My thoughts (Score:3, Insightful)
Re:My thoughts (Score:3, Informative)
Re:My thoughts (Score:3, Interesting)
This would seem to constitute a physical reference that is impossible to generate.
Just to state the obvious (Score:4, Interesting)
A new kilogram with equal an old kilogram. This will only make a difference to the history books and those who actually want to make thier own 'kilogram'.
I can imagine how many 'net savvy drug runners are looking at this and thinking, 'shit, I have snorted too much coke, does this affect my business? whats a planck? oh man, Avocado constant? [sic]
I say since the kilogram was an arbitrary measurement (in any definition) then why try and make it more formalised? I realised that celcius fit nicely with pure water at sea level freezing and boiling, and other measures have thier own basis (has the definitions have changed). Take my friend the meter. I always use the old skool definitions for rules of thumb.
Year Definition
1793 1 / 10 000 000 of the distance from the pole to the equator.
1795 Provisional meter bar constructed in brass.
1799 Definitive prototype meter bars constructed in platinum.
1889 International prototype meter bar in platinum-iridium, cross-section X.
1906 1 000 000 / 0.643 846 96 wavelengths in air of the red line of the cadmium spectrum.
1960 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between levels 2p10 and 5d5 of the krypton-86 atom.
1983 Length traveled by light in vacuum during 1 / 299 792 458 of a second.
So you see, a meter was the same in all these cases, but they just wanted to act clever.
The thing is, after world war 3, which measure will be easiest to revert to for a meter? trying to find scientist who can measure "Length traveled by light in vacuum during 1 / 299 792 458 of a second." or just comparing a brass stick with a length of wood while trying to build something using pre-existing specs (that you are relying on to build a post WW3 bridge).
Re:Just to state the obvious (Score:3, Informative)
Celcius is trickier than just temperatures of boiling and melting, because I think it must also declare the pressure too. The temperatures that water boils and freezes depends on air pressure. Kelvins are defined as divisions such that the range from absolute zero to the triple point of water is 273.16 kelvin. At least that doesn't depend on a the standard for pressure.
The problem with a meter standard depending on a ph
Why not gravity? (Score:3, Interesting)
Re:artifact (Score:3, Informative)
Re:artifact (Score:5, Informative)
Metre for Length
Kilogram (what this article is about) for Mass
Second for time
Ampere for current
Kelvin for temperature
Mole for amount
Candela for "Luminous intensity"
All the others are built up and defined from these, so these must be well defined. Change what exactly a Kg is changed more than just mass - it changes everything dependant upon it. Hence, these things must be got right.
The definition of second changes every now and then though, and I think the metre has changed a few times, too. I wrote a bit about the second here [f2s.com], in my AS-Level Physics coursework, if anyone want s a simplifed read.
(Wiki [wikipedia.org])
I don't see how this topics is maths, by the way.
Re:artifact (Score:5, Interesting)
"Candela essentially measures the same things as watts."
But watts are not a base unit. A watt is the same "Joules per second", and Joules is also not a base unit, but is defined as a Newton Metre. But a Newton isn't a base unit, it is defined as a Kilogram Metre per second per second. So:
Newton = kg.m.s^-2
Joule = Nm = kg.m.s^-2.m = kg.m^2.s^-2
So a watt is in-fact a kg.m^2.s^-3 , or "Kilogram metre squared per second per second per second" - hence changed the kilogram will change the watt, despite them seeming unrelated!
A mole isn't the same as mass at all. It is more to do with things on an atomic level. It's really used in chemistry - I've personally never used it outside of a chemistry exam (or coursework). It is sort of just a number, but it actually isn't.
Kelvin is a fundamental base unit too. Momentum is defined as "Newton Seconds", and so (remembering the definition of a Newton) kg.m.s^-1. Kelvin's measures temperature, which is a measure of kinetic energy, so I can see where you are coming from. You're just wrong.
Ampere is too. Helpfully, from it you can define other helpful things like volts. A volt, for your interest, is defined as kg m^2 s^-3 A^-1 , or "Kilogram metre squared per second per second per second per amp". And so yet another thing this change would affect.
It's all very interesting.
Re:artifact (Score:5, Informative)
In a fundamental system of units, there are three base units: charge, mass, and angular momentum. (Gee, those sound suspiciously like the three properties that a black hole can possess - I wonder why). Everything else can be derived from those units (for the most part - we'll ignore stuff like baryon number, lepton number, etc. because those theories aren't complete yet. For instance, we now know that only global lepton number is conserved, not mu, e, and tau lepton number separately. I won't even touch color, as color is completely hidden anyway).
In fact, the existence of those units can be derived from the fact that space is invariant under the Poincare group, and has gauge symmetry.
However, those base units come because you've defined other constants to 1.
The problem is that several of those constants are imprecise and difficult to measure. It is easier to define a kilogram, for instance, then it is to somehow base it on the gravitational attraction of two objects, because G is horribly imprecise.
Similarly, it is easier to treat Kelvin as fundamental rather than derived from other units *if* Boltzmann's constant has poor precision.
So while it's *possible* to use fundamental-based units, it's often *impractical* and less precise. The base units in SI are those that can generate all other units with no loss in precision.
To give a very practical example, the mass of a proton is typically given in atomic mass units (amu) as ~1.007 amu. You might think that it should be given in grams, as "amu" isn't a fundamental unit of mass. But the conversion from "amu" to "grams" is less precise than the mass of the proton in atomic mass units. So in this case, "amu" would be appropriate as a base unit, as well as mass, even though the two can be directly converted.
The benefit is that you can compare the mass of a proton and the mass of a neutron in "amu", for instance, to better precision than you could in grams. It's similar (or was similar when SI was developed) with the other units.
Re:artifact (Score:3, Informative)
Candela essentially measures the same things as watts.
Mole is just an number. It might be used in the definition of the kilogram, but in itself, it just relates the mass of a gram with 1/12 the rest mass of a carbon-12 atom.
Kelvin is just a unit derived from mass, momentum, and kinetic energy. It is not a base unit.
Ampere might or might not be a base unit, I'm not sure about that one.
You are talking about base units of physics (and you're still very wrong there), not base units of measurement.
Take Kelv
Re:artifact (Score:3, Informative)
The candela is a weird unit, but it is not equivalent to watts. There are three units related to light:
For som
Re:Anyone Else? (Score:5, Informative)
Re:Anyone Else? (Score:3, Interesting)
The question is, all the other units are "base" units, while the SI unit of mass has a (kilo) prefix; how come?
Re:News Why? (Score:3, Insightful)
Re: (Score:3, Insightful)
Re:How is the US pound measured? (Score:3, Informative)
Those who use pounds as force use slugs [wolfram.com] as the unit of mass. Same relationship as mass in kilograms and weight in newtons (i.e. Newton's 2nd Law), except for the weird-ass numbers.
Just how many hogsheads are there in a fortnight, anyway?
...laura
Re:It's all about the Bases (Score:4, Interesting)
THIS IS EXACTLY WRONG. In fact, this is why the imperial system is still in use - because it is largely base-12 in nature. Base-12 is far superior to base-10. The only advantage to SI metric system is that it is CONSISTENT in its conversions, where the imperial system is not. But using Base-10 for those conversions is a major headache, especially for bakers, carpenters, and anybody who has to frequently divide by 2, 3, or 4. The BEST system would be a metric/SI system that uses base-12. But I'm sure the Base-10 bigots will find reasons to disagree.
Re:It's all about the Bases (Score:4, Insightful)
Re:It's all about the Bases (Score:4, Interesting)
Baking is always cited as a reason for using imperial units. I enjoy making bread on a regular basis, and occasionally other baked tasty things, and let me tell you the Imperial system is virtually worthless when dealing with flour and to a lesser extent sugar and salt.
Any good bread recipe targeting the average American baker will usually state something to the effect of "3 to 4 1/2 cups of flour". That's not because the person writing the recipe didn't feel like specifying greater accuracy -- it's because volume is a horrible way of measuring flour.
To properly measure a cup of flour involves fluffing up the flour, gently filling your measure, and sweeping the excess off of the top. This is a pain and a mess -- you try effectively fluffing flour without creating a dust cloud, keeping in mind that this will often be done in a kitchen and that a cloud of flour is quite easy to ignite. Even when consistent measuring techniques are used the amount of flour in a given volume can vary considerably due to other factors, including the mill of the flour itself.
Generally, the experienced bread maker will start with an amount of flour that they know to be less than what they need, and work in extra flour as needed. This works with breads meant to be chewy, but as working the dough makes it more elastic this is less than ideal for more delicate items such as biscuits.
Things are further complicated when using volume to measure salt or sugar -- flake size can vary significantly, and the amount of variation in a tablespoon of salt (especially kosher salt, which has a generally large flake size and is easier to work with in the kitchen) can make a notable difference in the final flavor. Equal weights of sugars provide equal sweetening, but a cup of white sugar, brown sugar, and confectioner's sugar might weight 200, 220, and 120 grams respectively. Again flake size within the individual types of sugar varies from manufacturer to manufacturer. In addition to changing the texture and flavor of the product sugar affects the rise time and quality when yeasts are involved. Too much, and the product will expand too much, ruining the texture. Dough for breads is often worked, left to rise for flavor development, and then shaped into its final form and allowed to rise again. Too little sugar, and the dough's first rise may be its last, leaving you with a surprisingly dense and hard dough brick after baking.
By purchasing a quality digital kitchen scale, the baker can place the container to be filled on the scale, "zero out" the scale (which tells the scale to treat the reading it is currently getting as its "zero mass" point), and fill the container to the desired amount. This leads to easier conversion between various types of sugars, salts, and flours, including unintentional conversions when your particular brand of kosher salt has a larger flake size than that used by the person who wrote the recipe.
I just don't follow the justification that bakers have to commonly divide by 2, 3, or anything for that matter. Few people find, say, 1/3 cup by starting with a cup and dividing it into three parts. Even something such as filling a one-cup measure exactly halfway with flour or moleasses is quite difficult!
I'd say that it's just as easy given the proper tools, and more accurate in terms of the actual amount of the ingredient involved, to measure 50 grams of sugar as it is to measure 1/4 cup. In either case, nobody is dividing anything, simply using the proper measuring device. In the case of the recipe calling for 40 grams of sugar, though, the SI system has a clear advantage. The SI baker would add to the scale until it read 40g. How about 40 grams of sugar (80% of 1/4 cup) in terms of standard Imperial measuring devices?
Google calculator gives "80% of ((1/4) US cup) = 4
Re:A kilogram is not abitrary. (Score:3, Insightful)
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