Everett had his 9 month checkup last week.  After the exam, the doctor had no concerns and reassured us that he appears healthy and is doing well.  Later that night when I glanced at the materials sent home from the doctor’s office I couldn’t help but notice the hodgepodge of units that were used to measure him: weight in pounds, height in inches, head circumference in centimeters, and medication dosages in milliliters and teaspoons.  I suspect this has to do with who manufactured the different gizmos they have around the clinic for doing such measurements, but it could also be a reflection of the Standard & Customary system of units we use in the US, with a heavy emphasis on Customary.  I call it the Weights & Measures Variety Show.  For example:

1. Why do the units of volume depend on what is being measured?  Why is corn measured in bushels, beer in kegs and oil in barrels?

2. Why doesn’t an ounce of gold weigh the same as an ounce of water?  On a similar note, shouldn’t a gallon represent the same volume of water in England and the US?  (Answer: yes, but it doesn’t)

3. Why do we measure body mass (e.g. kilograms) with units of weight (e.g. pounds)?  To clarify, mass is a physical property of your body while weight is a reflection of the local gravitational field.  That’s why your weight would change if you traveled to another celestial body such as the moon, which has a much weaker gravitational field (but much more sensible economic policies).  At this point you might be thinking “My weight is the same everywhere on earth; therefore, can’t it be though of as a surrogate for mass?”  The short answer is no.  The earth’s gravitational field changes depending on where you are located (see this map for details, or you can view the Google Earth version here), which is perhaps why Grandad Cress sometimes finds high gravity zones where things are more likely to be dropped.

But getting back to babies, a relevant example is the way that we size clothing.  In many parts of the world you can select infant clothes by 1) measuring the length of your baby in centimeters and 2) finding clothing with that size printed on the tag.  It’s a simple, straightforward system.  However, in the US we measure baby length in units of time: clothing is sized according to age in months. So if the tag says 18 Month Boy then that means it was probably made for a baby between 30 and 34 inches and weighing between 21 and 32 pounds.  This makes about as much sense as sizing adult clothing by age, and it is a great illustration of the silliness of our system of measure.  Why don’t we switch to metric?  Probably because most parents, myself included, find metric units non-intuitive (e.g. I have no idea what 20 degrees Celsius feels like).  However, it’s probably more accurate to say that metric units are unfamiliar, since it would be difficult to come up with a system more counter-intuitive than the one we use now, to which some respond “Yeah, our system is strange and inconvenient, but what’s the worst thing that can happen?”  Well, one thing that could happen is medical errors resulting from incorrect measurements or dosages, which is why the National Coordinating Council for Medication Error Reporting & Prevention recommends using metric: “The change to use of the metric system from the archaic apothecary and avoirdupois systems will help avoid misinterpretations and miscalculations.”  Another thing that could happen is that you could incite inter-planetary conflict.  That’s what NASA found out when they flew a perfectly good orbiter into the surface of Mars (see http://www.cnn.com/TECH/space/9909/30/mars.metric.02/).  Note the first line of the story: “NASA lost a $125 million Mars orbiter because a Lockheed Martin engineering team used English units of measurement…”.  So there you have it: English units cause spacecraft collisions.  $125 million may not sound like much given recent economic events, but keep in mind this was in 1999 so those were Clinton dollars not Bush dollars, before billion became the new million.

I’m getting a bit off topic here.  But I’ll wrap up by saying that we pick clothes for Everett by ignoring the size on the tag and holding him up to the garment, or vice versa, which works great if he is shopping with you but is a challenge for those who buy him clothing but see him less frequently.  And that is a perfect segue into our next blog entry on Grandparents…

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