Post-Halloween Special! You’ll be Metrified!

Why hello there Paleo-Posse! Long-time, no-see!

It’s Jacob here! Back from an extended vacation from the blog. In case you missed it, I got married, went on a not-long-enough honeymoon, and now I’m back to the grind. Did you miss me? I missed you!

Thankfully the Caribbean is full of fruity drinks that helped me keep the urge to supply SCIENCE to the Paleo-Posse in check, at least while I was on my honeymoon.

Unfortunately, a disaster is about to impact fruity drinks everywhere!!!


I don’t know if you heard, but France is about to screw up everything for the rest of the world, AGAIN.  (As if their World-class health care system wasn’t enough, SHEESH)  Apparently, they haven’t been taking good care of this random chunk of Platinum that some dudes carved up in 1879 and decided to name “kilogram.”

Kilogram, say Hello to the Paleo-Posse….KILO! SAY HI TO DADDY’S FRIENDS!!

Ok, so it obviously wasn’t that simple, or stupid. So let’s back things up.

What is a “unit” of measure?  What is a kilogram or a pound or a foot or a second, except for something that a scale or ruler or stopwatch can measure?  Who tells the ruler how long a foot is, or how much a “slug” is?

Well somewhere, sometime, someone had to get other people to agree on what defines those different units of measure.  Some units of measure, like meters and seconds, have “practical realizations” that rely on universally unchanging constants, like the speed of light, to allow the exact definition of the unit to be experimentally derived by labs anywhere, allowing the precision of the measurement to get better with technology.

Unfortunately, not every unit measurement (mass in particular) has yet been linked back to the speed or light or other universal constants, and therefore a “control unit” must be kept to serve as the ultimate definition of the unit.

In this case, the control unit is known as the International Prototype Kilogram, or the IPK.  The IPK is a cylinder of 90% Platinum and 10% Iridium that was made in 1879, and is defined as exactly 1 kilogram.

Every measurement of mass IN THE WORLD, is made against the assumption that this simple cylinder has a mass of EXACTLY 1kg.

Let that roll around in your head a little bit…

So basically what happened is that everyone made copies, or cuts from the same ingot of the alloy made for the IPK, and went off and calibrated all of their scales based on these control unit copies.

Now because of a variety of effects, some understood and some not understood, the mass of these copies has changed somewhat significantly.  Every once in a while, there is a periodic verification where the variances in all the copies are compared and normalized against the IPK.  This way, the total degradation seen among the entire set can be observed and accounted for.

At a certain point, however, the total amount of degradation WILL become significant enough to affect calculations and measurements around the world.  And that point is…Now.

It is estimated that the IPK itself has lost around 50 micrograms since 1879 (though the term “lost” may not be accurate, as it gains weight from adsorption, and loses it again from careful cleaning), while the control copies have “lost” more or less depending on their uses and environments.


Over time, the changes in mass of the control copies were observed and recorded.  The variance (i.e. the amount that the mass changes with each measurement) of the individual copies are different than each other copy, because of their unique storage environments, handling conditions, and maintenance methods.  In a statistical data analysis, if two samples which are ASSUMED to be from the same population (i.e. two control copies) are observed to have vastly different variances, then there is a high probability that they are NOT from the same population.  What this means is that the “periodic verification” is no longer statistically valid, because there is too much noise in the data.  Since the verification process is becoming invalid, the “true” value of the kilogram is becoming…fuzzy.

Did I lose you there?  Stay with me for one more minute…

Since the mass values of each control copy are diverging, rather than changing in similar and predictable manners, the assumptions and corrections that have been made up to this point to derive the “original” value of the kilogram are slowly becoming less accurate.  Therefore, the value of the kilogram is losing precision, and consequently losing validity and scientific certainty.


TL;DR: The value of “1 kilogram” is changing – because of the manner in which we defined it – and we don’t want it to, because our alcoholic recipe’s depend upon it’s accuracy.  Also, it’s clearly France’s fault  (not really).

So how do solve this problem?  AMERICA, that’s how.

Not as sexy as a fighter jet, but she gets the job done…

NIST has developed a device called a “Watt Balance” that is able to correlate mass with an  electrical charge, using only the speed of light and Planck’s constant in the experimental calculations.  From the way it looks, this is going to be the new definition of the kilogram very shortly.

BONUS POINTS: Did you know that the Metric system is the “Official” system of measurement for the United States, and has been since 1975? Don’t let all those speed limit signs, thermometers, and rulers fool you; in the USA we use the Metric system gosh darn’it!!!  Er, at least, we’re supposed to?


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3 Responses to Post-Halloween Special! You’ll be Metrified!

  1. JustinNo Gravatar 7 November, 2010 at 7:55 am #

    The metric system can’t even get the kilogram right! That’s why the aerospace industry prefers to measure things in units that make a TON (that’s 2000 lbs) more sense, like slugs, foot-pounds, inch-pounds, pound force, pound mass, and lengths based on a long-dead monarch’s foot length.

    Far superior to a stupid platinum cylinder. Obviously.

    • JacobNo Gravatar 7 November, 2010 at 3:05 pm #

      Totally agree.

      I don’t know what I would do if I had to measure stress in Kilo-Pascals!

      Our current preferred system of units for stress and strain is the bastard-child of metric and English units, so we use Kilo-Pounds-per-square-inch, which is abbreviated as “ksi” (herp?), and kilo-pounds, which is abbreviated as “kips” (derp?). I still don’t get it.


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