
Metamorphosis and Millimeters - colinprince
http://themetricmaven.com/?p=85
======
eCa
I am a non-engineer who has used mm/cm/dm/m/km all my life. For me, 1 km is
not necessarily 1000 m, and 5 cm is not necessarily 50 mm.

In everyday use using only the smaller unit implies a precision that usually
isn't there.

Millimeters certainly has its place, but so do centimetres.

~~~
slyall
I remember when I was at school the first day of woodwork class (age around
10) we were told that all measurements were in millimetres.

I don't think anybody had problems adjusting. It was just another thing to
remember in class.

Outside the class everybody used mm/cm/m/km as needed (nobody used dm where I
lived).

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rdtsc
Hmm, don't see a big deal. Maybe it is a big deal to someone striving for some
engineering beauty and consistency, but in every day life, centimeters and
decimeters even are popular because they relate to sizes on human scale --
size of a palm, thickness of a finger and so on.

But I grew up with those units and didn't encounter them first in the
university or high school. Just have everything be divisible by 10 is easy
enough and knowing the prefixes is easy.

I was very confused and still am by inches, yards, stones, pounds, ounces,
gallons. I don't know how many in each of each.

~~~
ralfd
I never encounter decimeter. Centiliter only for shot glasses, every kitchen
measure thing I have only shows mLiter. Same with grams. There are no
centi/decigram on my kitchen weighing scales.

~~~
kwhitefoot
deciliter is very common in cookery here in Norway.

------
Oletros
Is this a thing than only happens in countries that doesn't use the SI?

I don't know of anyone that has a problem using m, cm or mm in different
circunstances

~~~
Symbiote
Me neither.

I remember one of the educational toys my school had, which I played with when
I was 5 or 6. We called it "tens, hundreds, units" [1]. There were many
1×1×1cm "units", 10×1×1 "tens", 10×10×1 "hundreds" and a 10×10×10 "thousand".
You could fill the hundreds and thousand with water, the thousand obviously
being 1L.

The British National Curriculum [2] says children \- In year 1 (age 5-6)
should be able to count centimetres \- In year 2, recognise place value,
choose appropriate units (cm/m, g/kg, °C etc) and use measuring tools for
these \- In year 3, to add milli- to that, \- In year 4, convert between
centimetres and metres, and other units (time and £ and pence) \- In year 5,
to convert between milli-, centi-, base, and kilo- measures. Calculate square
areas in cm² and m² \- In year 6, volumes in m³ etc, and converting
everything, to three decimal places.

(This hasn't changed since the 1960s or something, so it's a shame the country
won't get rid of road signs with miles and yards on.)

[1] [http://www.tts-
group.co.uk/shops/tts/Products/PD1723354/Base...](http://www.tts-
group.co.uk/shops/tts/Products/PD1723354/Base-Ten-Class-Set/)

[2] [https://www.gov.uk/government/publications/national-
curricul...](https://www.gov.uk/government/publications/national-curriculum-
in-england-mathematics-programmes-of-study/national-curriculum-in-england-
mathematics-programmes-of-study)

~~~
DanBC
Some people know those as cuisenaire rods.
[http://www.amazon.co.uk/gp/aw/d/B00074U7SO/](http://www.amazon.co.uk/gp/aw/d/B00074U7SO/)

[https://en.wikipedia.org/wiki/Cuisenaire_rods](https://en.wikipedia.org/wiki/Cuisenaire_rods)

They're brilliant, but go careful with some of the work books that are
available. ("Blue + red = ?" cause confusion.)

------
ex3xu
As a first generation Chinese-American, I run into a similar problem
converting back and forth between Chinese and English -- where English only
has words for thousand and million, the Chinese prefer to speak in units of
ten thousand (wan). You get a feel for how unintuitive it is to say things
like "twenty-five ten-thousands" to read the number 250000, or "a thousand
ten-thousands" for ten million.

With regards to why America doesn't make the change to metric, I recall
reading somewhere that the American manufacturing base didn't want to have to
convert all their infrastructure, currently set up to manufacture screws,
bolts, and other such tools in units of inches, half-inches, five-eighths
inches and so forth. It's not just a question of cultural shifts in intuition
-- there's a physical cost associated with making the change as well.

Knuth's quote comes to mind -- the root of all evil being premature
optimization. I wonder about the full price when you integrate the little
costs of these scenarios of suboptimal standards -- not just in the realm of
physical measurement, but the QWERTY keyboard, pi vs. tao, English grammar
rules, even the base ten number system among others. But at some point you
have to declare "good enough", and stop refactoring to instead pay upkeep on
the accumulated technical debt. Perhaps it is a shame that America chose not
to refactor to metric, but maybe some day down the road we will find a
generation generous enough to raise their children with better-optimized
standards, and pay the costs of re-learning a new intuition themselves.

------
avmich
[https://en.wikipedia.org/wiki/Natural_units](https://en.wikipedia.org/wiki/Natural_units)

You can use units which are very neat and pretty logical for some things - and
very inconvenient for others.

That's, I think, the reason we have all that variety of units, which don't
quite follow the same system. Centimeters are there just because of utility in
less than strict cases; may be brains are simplifying by dropping unnecessary
precision digits from consideration. Same for Kelvin - we don't measure
temperature in, say, electron-volts, not only because Volt isn't a natural
unit.

------
Someone
_" There is one odd-man-out: Celsius."_

Two remarks: firstly, the unit for temperature is kelvin. Secondly, and more
importantly I don't see how temperature would be special. The second is a
larger outlier. Whe have milliseconds, microseconds, etc, but rarely use
kiloseconds, megaseconds. Another outlier is angles, where degrees, minutes,
and seconds are used more often than radians. More examples at
[https://en.m.wikipedia.org/wiki/International_System_of_Unit...](https://en.m.wikipedia.org/wiki/International_System_of_Units#Retention_of_non-
SI_units)

------
nraynaud
As a side note, the French (at least) architectural drawings are in
centimeters, that's the only place I have seen centimeters as the default, but
it's one of the most important engineering field.

~~~
Symbiote
Are you sure? "ISO 129 Technical drawings -- Indication of dimensions and
tolerances" specifies that SI units be used, i.e. µm, mm, m, km.

I've only seen British drawings, which almost exclusively use mm for things up
to the size of a moderate building (school etc). I've seen metres used on
really big things, like 10km of railway.

~~~
nraynaud
I just did a random google image search in French:
[http://www.jeanbellanger.com/data/5190/f1f0/d3476/thumbnail/...](http://www.jeanbellanger.com/data/5190/f1f0/d3476/thumbnail/x1410-y885-tfill-k65/jean-
bellanger-architecte-plan-entreprise-moderne-angers.jpg)

(it looks like this architect doesn't really understand the concept of
thumbnails)

I think architecture is using a separate set of rules than mechanics.

------
jacobolus
It’s quite unfortunate that the SI system of units is built on top of the base
10 number system.

If we all switched to base 12 instead (especially if we likewise unified
measurement for time, angles, geographic coordinates, money, etc.), the
arithmetic would be much friendlier for humans.

One example of a base 12 metric system:
[http://www.dozenal.org/drupal/sites/default/files/tgm_0.pdf](http://www.dozenal.org/drupal/sites/default/files/tgm_0.pdf)

~~~
chm
Please give me an example of how base 12 arithmetic is "much friendlier" than
base 10.

I've just skimmed the PDF... it looks interesting but a bit cranky. I'll edit
when I have a better idea. Table 9 is just... ridiculous to me.

~~~
ubernostrum
Outside of scientific and engineering fields, most everyday interactions
people have with their units of measure do not involve translating between
orders of magnitude, and yet the metric system optimizes for that to the
exclusion of all other conveniences, through its focus on base 10 and "it's so
easy, just move the decimal point!"

Meanwhile, in most other areas of life, dividing into halves, thirds or
quarters is overwhelmingly more common than dividing into tenths, hundredths
or other powers of ten. If you wonder why the "unintuitive" imperial units
have such staying power, consider that 12 and 16 are more typical bases for
them, and 12 is essentially ideal (evenly divisible by 2, 3, 4 and 6) while 16
is better than 10 (evenly divisible by 2, 4 and 8).

~~~
Symbiote
Nothing stops you taking the advantage of both.

Kitchen cupboards, appliances etc are designed in multiples of 300mm, which
has factors of 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 25, 30, 50, 60, 75, 100, 150,
300. The smallest part is still in mm, not awkward fractions of an inch, and
the whole wall can be put in mm: 3880mm. That's easy to understand, but 152
inches is less so (who uses inches for something that long?). 12ft 9in is
presumably intuitive for those familiar with imperial, but annoying to convert
as soon as it needs dividing or multiplying.

Also, imperial units didn't have much staying power in the ex-British Empire,
apart from in Britain.

~~~
ubernostrum
_Nothing stops you taking the advantage of both._

I think the main question is why we feel a need to impose a single one-size-
fits-all universal unit set onto disparate domains with different ideas of
what properties make a unit desirable. There are domains where base-10 units
are a good fit, and other domains where base-12 units are a good fit, and I
don't see why we need to try to force one set of units to serve both.

~~~
Symbiote
Because mistakes happen when people use systems they aren't familiar with, and
the mistakes can be expensive, dangerous, and sometimes even fatal.

Here's one example:
[https://psnet.ahrq.gov/webmm/case/293](https://psnet.ahrq.gov/webmm/case/293)

If the nurse had been used to working in kilograms, she would have realised
25kg was a huge sack of coal / much bigger child / whatever. (She would have
known that her own weight as a child was 40kg or whatever.) Or, if the country
had been properly metric, the scale wouldn't have had the option of pounds.

(Hopefully, you see no reason to divide a child into 3, 4 or 6 equally massed
parts.)

~~~
ubernostrum
So... the metric system magically prevents data-entry errors? Or somehow you
can't believe that there actually are common everyday tasks involving
splitting something into halves, thirds, quarters, etc. and so feel a need to
engage with a hyperbolic child-dissecting strawman instead?

You're really not doing a great job of presenting your case here.

------
powera
It's almost as if the metric system was designed to be _useful to ordinary
people_ rather than to fit a nice-looking model of units.

Most people use a ruler or their hands to measure things, not dial calipers.
And most people don't want to have to say "230 millimeters" as opposed to "23
centimeters" (or more realistically, 20 centimeters).

~~~
ciconia
The old 12-base system is actually very useful once you put your calculator
aside. Dividing 1 foot by 4 is much easier than dividing 30cm.

Also regarding your comment on mm vs cm, in my line of work (organ building
[1]), we always talk in mm, just to prevent confusion, even for lengths of
multiple meters).

[1] [http://www.blumenroeder.fr](http://www.blumenroeder.fr)

~~~
avmich
> Dividing 1 foot by 4 is much easier than dividing 30cm.

That's of course very subjective. One has to remember that 1 foot is 12
inches, where in metrics one only remember once all prefixes and applies them
to all units uniformly.

------
ralfd
The blog was posted 3 years ago. Sadly the link to the lecture on
video.google.com rotted away since then, as if google was geocities.

~~~
teddyh
It’s probably this one:

[https://www.youtube.com/watch?v=JjBWJbHtYHo](https://www.youtube.com/watch?v=JjBWJbHtYHo)

I agree, though – the Google Video URL invalidation is a _discrace_. One would
think that Google, who _owns_ YouTube, should be able to create 301 redirects
for all _its own_ videos to their location on YouTube.

~~~
agumonkey
A little web.archive.org confirms year and title.

I agree about the second point, Google really has been too busy being socially
fancy and letting their old resources rot stupidly. Noobs.

