The Metric Caboose

By The Metric Maven

Mini-Bulldog Edition

As a boy, I lived less than a block from a set of railroad tracks. The report of train whistles, and the low pitched sound of each train as it passed by during the night assured me commerce was underway, and all was fine. During the day, myself and others would often watch as a train passed to see what the oldest car was. The oldest was 1909 as I recall, and those cars looked very fragile. Of course the caboose was a punctuating symbol that defined the end of the train. I don’t ever recall a caboose at the front of the train. A caboose at the front of a train, before the engines, would be seen as something out of order, that is not being used as designed. Could one hook a caboose to the front of a train and have it operate? Sure—does it make sense–perhaps—but not as expected usage.

When I first became interested in electronics, resistors were the first component I encountered. Their resistance is measured in ohms. One might have 50 ohm resistor, or 68 ohm resistor, but when the value progresses into the thousands, the metric prefix Kilo is used. A 10 000 ohm resistor is a 10 Kiloohm resistor which is generally written as 10 KΩ, when the resistance becomes large enough we use Megaohms or MΩ. As people like to speak in shorthand, and everyone knows, that on an electrical schematic, resistors are in ohms, electrical engineers generally say “that’s a 4 K resistor,” implying that the value is 4 KΩ. When people say they are going to participate in a 5K run, it’s understood that it is a 5 Km distance.

The metric prefix Kilo- is supposed to modify the unit value that follows it, but in common usage, people often appear to use it as shorthand for a set of zeros. When the prefix symbol is moved next to a numeral, 5K becomes 5000; the prefix modifier becomes a suffix modifier. When it is thought of in this way, it can be used as a sort of stealth prefix for Ye Olde English, or whatever comes along.

For instance here is an example from the web where the metric modifier is separated from Olde English as if this is a good idea:

So it reads “Spruce beetles pick up where their pine cousins left off, eating through 136 000 acres in past year” rather than “Spruce beetles pick up where their pine cousins left off, eating through 136 Kiloacres in past year.” The prefix modifier becomes a suffix modifier and metric is “compatible” with anything. Just by removing a space we modify the leading number rather than the trailing unit. By invoking this idea, we create 5K dollars, or 75K crickets, or 210K albatrosses. This space removal causes a literary switcharoo that turns a prefix into a suffix. This appears to be a practice that has happened somewhat recently and has become an accepted part of the language. If there is no space between it and a leading number, the single metric “prefix”  becomes a suffix number, and if there is a space then a metric unit must follow the prefix.

Is this usage a good idea? I’m not sure. Perhaps this is a usage that could make sense. Without a space 326K, or 326M, or 326G could be thought of as numbers. The value 326G certainly is more compact than 326 000 000 000. This distinction would have to be identified, formalized, and taught in schools, so that students would know how to use it properly. If one writes 25K they mean a number, if they write 25 K then one should expect a unit symbol to follow such as 25 Km, and 25 K would not be considered a finished statement. I can see how this usage could be useful, but currently it strikes me as the engine switched for the caboose.

Related essay:

The Elements of Bile

The Metric Maven has published a book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.


Realm of Measure

Realm_of_MeasureBy The Metric Maven

Bulldog Edition

It can be interesting to read books from a bygone era about measurement. The current attometer per Zettasecond pace of metric change in the US requires one to look back historically to notice any change at all. I recently read the 1960 book Realm of Measure by Isaac Asimov. It is an interesting time capsule with which to compare the world of 1960 to current times. Early in the book (pg 4) Asimov asserts:

Even in modern times we are still refining our measurements. And although the world’s nations quarrel so desperately that it would seem they could never agree on anything, all have been honestly co-operating in the establishment of international systems of measurement.

Asimov’s statement indicates that more than one international system of measurement exists in 1960. This makes sense because it was in 1959 when a number of English speaking countries (including the US) finally decided to agree what the length of an inch is—well actually a yard—in terms of the metric system.

After Asimov presents pages of complicated units such as chains and the Russian verst he states (in 1960s vernacular):

Well, surely, you might think, the ingenuity of man can work out a better system. If you think so, you are right. The ingenuity of man has indeed worked out a better system, and this was done a hundred and fifty years ago. Unfortunately, we, in the English-speaking countries, have chosen not to benefit from it.

This better system is of course the Metric System.

Asimov spends time on centimeters and Kilometers in Chapter 3. Twenty-Three years later, when he writes his book The Measure of The Universe, Asimov realizes the non-utility of centimeters, centigrams, centiliters, and so on and makes this clear to his audience. But in 1960 he still introduces a table to convert from hectometers to dekameters, to decimeters, to centimeters. I have argued in the past, that from a twenty first century perspective this usage appears unnecessarily complicated, but when viewed in comparison with the plethora of US Anarchy Units of the era, even this bloated version of the metric system looks like a significant simplification (page 44-47).

The good doctor goes on to introduce the micron (pg 47):

For instance, people who work with cells, bacteria, viruses, and other microscopic objects find it useful to deal with the micrometer, which is one thousandth of a millimeter. (The prefix “micro-” comes from a Greek word meaning “small.”) This unit is very commonly abbreviated to micron, but I think this is sloppy because it hides the relationship to the meter.

Indeed, the micron is still a blemish on the metric system.

The notion of concatenated prefixes is still embraced at this time, which also balloons the metric system with unnecessary complication:

A thousandth of a micrometer is naturally called a millimicrometer, a unit which is invariably abbreviated to millimicron. The millimicrometer is a billionth of a meter and in 1960, the National Bureau of Standards has adopted the prefix “nano-” for a billionth. The millimicrometer may therefore be called the nanometer.

There is also a fatalism and acceptance of eponymous units:

..This unit [nanometer] is small enough to be used conveniently in measuring the lengths of light waves. The Swedish astronomer Anders Jonas Ångstrom suggested, in the 1860s that a tenth of a millimicrometer be used for this purpose. That length could be called a “decimillimicrometer,” I suppose, but no one ever uses that term. It is called simply an Ångstrom unit, in honor of the astronomer. Again, no one can tell from the name what the relationship is to the meter, but the thing is done, and cannot be changed.

The concatenated prefix fun of 1960 does not end there, we can even embrace the bicron if we want (page 48):


The accepted unacceptable ideas of 1960 continue when Asimov explains a contemporary desire to introduce a new unit called the X-unit! A division of this unit would be in honor of Enrico Fermi! Yet another eponymous unit. Here is a table from the text:


Asimov mentions the barleycorn and the mil, which is a feral unit that should have been vanquished from usage decades ago in the US, but is still used ubiquitously in the US Aerospace industry.

The gentle doctor argues for an idea that history and experience will squarely weigh-in against, metric gradualism. If the metric system is slowly introduced in schools he argues, the later adults would not find it so foreign:

Then, little by little, metric measurements should be introduced into common use, without necessarily replacing the common measurements. For instance, distances between cities might be given in both kilometers and miles on road maps. (pg 34)

Dual units only encourage the use of old units. This is clearly the situation in the US. Metric gradualism may eventually work, if one waits 1000 years or so.

The metric system of 1960 often accepts a pre-metric style of usage:


The Megagram is then dissed by Dr Asimov:


Asimov does not indicate that the term Megagram should be commonly used, and just accepts the current farrago of homonyms, where a metric unit is interpreted using a pre-metric Ye Olde English term for context, but I must remember, this is the world of 1960. Unfortunately, it is also the world of 2016. No one seems to notice that metric ton has nine letters and Megagram has eight. So why is the term metric ton so much more acceptable? Too many syllables?

The book lurches back and forth between cgs and mks expression which produces an intellectual vertigo. This dichotomy has always appeared to me as a proxy war between a Ye Olde English usage of the metric system (cgs), with the centimeter as a pseudo-inch, and mks, which would become SI. This struggle continues in the US, but is invisible to its participants. I see cubic centimeters and centipoise used regularly in the US.

One can be thankful that the use of millimicrons, quintals, myriagrams and such have apparently receded into history, even if the micron has not. The idea of X-units, fermis and bicrons have also exited from view. Unfortunately in the US, it is only omission of these bad practices that produce any noticeable change, as metric usage in the the US is of little consequence in the life the average person. It is easy not to use X-units, fermis and myriameters when the entire metric system is invisible in the US, but this omission is not exactly progress.


The Metric Maven has published a new book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.