Slashdot Mirror
The Changing Definition Of 'Kilogram'
DrLudicrous writes "The NYTimes is reporting that the platinum-iridium standard mass for the kilogram is shedding at an appreciable rate -- at least compared to other reference masses. The Pt-Ir cylinder is kept in France, and measured annually, and the slight discrepancy is important because the kg is an SI base unit- thus other quantities such as the Volt are based on it. A new standard is being sought- the two frontrunners are counting the number of atoms in a perfectly spherical single crystal of silicon, and another technique uses a device known as the Watt balance."
And since the inf^H^Hmperior^H^Hal system is now defined in terms of the metric system (an inch is 2.54 cm), your strange units change as well.
I for one welcome our new SCOviet Russian overlords to whom all our base are belong.
Since there is only one reference object for the kilogram, everything else is just a copy -- and even if it is a first generation copy, errors are bound to creep in.
The redefinition of the kg is long overdue, mad props to the scientists working on this.
It seems they should just reference the kilogram to a standard, such as x,xxx,xxx,xxx Si (28 isotope) atoms. This would eliminate the complications trying to build a standard, duplicate it and correct for earth's gravitational variations at the time and place of checking physical reference mass (not weight, to which the article alluded). Keep in mind the kilogram is a measure of mass, and not weight. That is why maintaining a physical standard requires correcting for gravity at the location's, time, elevation, tide, (add geophysical conditions, ad nauseum) of measurement.
If we are maintaing a physical chunk of alloy as the standard, it's time to decide on a more precise measurement, like we did with the meter long ago.
What i've never understood is since the kilogram is the base unit why didn't they just call it the gram?
" It's not a matter of dark ages, it's a matter of infrastructure... while not the largest country in the world (the US is probably third or fourth, I'm not sure), we have by far the most technological infrastructure. It is not feasible to change all that in a short period of time."
Bingo! this is why the US has been working on the process so long. Granted the push hasn't been very great but it's happening. If you're a country of a few million and only are the size of a small new england state, the change is pretty cheap and easy. When your huge, there is a massive infastructure change cost. and trying to re-wire 300 million peoples brains to a new way takes a lot more work.
I think places like Europe were also helped by war. They had to rebuild and start new with so much. So it was a perfect time to start fresh. The US is a pile of legacy ways. And nothing happens to change them.
With that said I wish we would try harder to convert. Get a dual system going now and run it for 20 years. let people adjust. Teach school in 95% SI ( only enough english units stuff so the comprehend them).
Perhaps we don't have the coercive state apparatus necessary to 'make' the metric system the primary system that we use.
Me, I have been doing a lot of woodworking lately. It's convenient to use a unit (the Foot) that divides easily into subunits that are multiples of both 3 and 4, without having to get all mired in floating point arithmetic.
But we have this metric flamefest every time the metric system comes up on Slashdot, and the same crap comes up every time.
I'm just happy that pointy-head metric zealots don't seem to have much pull in the real world of regular people. Keep on ranting, dudes.
You do know the metric system is many hundred of years old don't you? In fact it's older than your country. The point is the US has had 200 years and they haven't even started the process. There's nothing saying you can't run in parallel - the UK has been doing so for years. It's absurd to say you have to rip out all the imperial pipes and replace them - you just have to keep 2 sets of tools around until those old pipes get replaced naturally. It really isn't hard, it's just the US can't be bothered.
---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"
If the volt was based on the kilogram (and therefore a relationship exists between the two), and now volt is based on frequency, isn't it possible and wouldn't it be a good idea to base the kilogram on the volt? Then we don't need those perfect references anymore.
This sig under construction. Please check back later.
As the poster below me said, you are quite wrong.
The point is the US has had 200 years and they haven't even started the process. There's nothing saying you can't run in parallel - the UK has been doing so for years. It's absurd to say you have to rip out all the imperial pipes and replace them - you just have to keep 2 sets of tools around until those old pipes get replaced naturally.
No, you really don't get it at all. As it happens, most people who have tools ALREADY have the two sets of tools. What makes switching difficult is having two sets of PARTS. It's all well and good to say "from now on all parts/raw materials will be measured using the metric system", but what does one do about, say, electrical conduit fittings? There is an UNGODLY amount of installed bass there which is already in inches and adding on to it would require a complicated system of adapters and a complete recalculation of wire capacity. Name any other construction trade and you run into the same thing. How do you add on to an inches-and-feet house with metric lumber? What size metric ducting do I buy to add to a 12-inch heating plenum? Not saying that it can't be done, but there's a lot more to it than "keep[ing] 2 sets of tools".
If a job's not worth doing, it's not worth doing right.