Converting to Metric
Today’s xkcd is, like most of Randall Munroe’s comics, genius.
The jokes are, of course, funny. But Munroe makes a really good point here in his top-center “key to converting to metric”. Students never get a really good sense of what metric is because of how it’s presented. Just about every teacher says something to the effect of, “This is an inch, this is a foot, this is a pound. There are centimeters and meters and kilograms too, but you’ll just about never use them.”
We’ve all seen it in textbooks. There will be a passage like this: “The average weight of an American man is 175 pounds (79.379 kilograms).”
A metric conversion, when it’s given, is a complete afterthought. It’s presented with a ridiculously high number of significant figures, fresh from the calculator of the editor responsible for making sure the book sells well in Canada too.
What does this say to students? Everyone loves 175 pounds! Who would really give their weight as 79.379 kg anyway? Screw the metric system!
Even favoring English units over metric, my former students, surprisingly, didn’t really know how heavy a pound is or how far 100 feet is. Math teachers spend so much time teaching students that there is one correct answer that they forget how important estimation is in real life. So we might as well work on drilling centimeters and kilograms into their brains while they’re still open to anything.
Metric isn’t about conversions, it’s just another way of seeing things. It’s a slightly different language, one that the entire rest of the world is comfortable with.
Americans have a world-famous sense of entitlement. Our rabid adherence to meaningless tradition generally leads us to avoid that which is easy, sensical, or superior, in favor of that which is more complex or vastly more expensive. (How many Sacagawea dollars have you seen around lately?)
Despite all this, America really does use metric when it counts. Scientists use the metric system pretty much always. Engineers use metric as much as possible, though they’ll still pull out a twelve-inch ruler when working with old toolsets or equipment. Does it matter that speed limit signs say “50 mph” instead of “80 km/h”? Probably not.
But despite the economic downturn, globalization is still happening. Something as apparently inconsequential as our preferred system of measurement is important so that we can remain conversant with the rest of the world. It’s important for our students and us to become not just familiar with metric, but comfortable with it. Not just as a means to convert numbers from one language to another, but as a way for all of us to speak the same numerical language.
Tags: comic, estimation, funny, measurement, metric, munroe, numbers, si, xkcd
Physics Is Phun | Jim | 
January 5, 2009 10:15 pm
16 Comments
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The Evil Eyebrow » Metric (SI) vs. English (Imperial) — January 6, 2009 @ 9:46 am
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By Aaron, January 5, 2009 @ 10:51 pm
Well said.
Its a personal pet peeve of mine when I hear someone talking physics in American units. Like foot pounds. *Shudder*
By Annie, January 5, 2009 @ 11:10 pm
Personally, I wish the U.S. had gone metric in the 70s. Every time I’m stuck trying to do conversions in the grocery store, I wish there was an easier unit. And how screwed up is it that ounces can refer to fluid volume and to mass?
M had to explain to a customer the other day that she couldn’t do a blanket “How many cups of X in a pound?” conversion. She didn’t get him when he said it depended on what X was. A pound of sugar will provide fewer cups than a pound of Splenda.
I had to point out to him a confusion of the sales tag labeling in the store after watching a poor soul trying to figure things out. The sign said the 128oz. milk was on sale. However, all the milk is labeled by gallon (or quart) with no ounce equivalent on the packaging.
By Bill Ruhsam, January 6, 2009 @ 7:40 am
@Jim, I’m confused. Are you saying that the Sacagawea is a good thing? The only good thing about it, in my opinion, is that it’s shiny and confuses the fast food clerks when I use it to pay. I hate coined money.
@Aaron, not that I don’t agree with you, but doesn’t it also show a person of unique capability who can talk in both kilograms and slugs?
By Bill Ruhsam, January 6, 2009 @ 7:42 am
Oh, and I guess it’s a good thing that Randall Munroe has definitively answered the age-old question of how much a caption masses.
By Jim, January 6, 2009 @ 8:41 am
@Bill Ruhsam:
I liked the Sacagawea. Most people hate coined money because they never spend it.
I contend that we constantly let change build up in our pockets because in this country coins are virtually valueless for anything but the most trivial of purchases.
When we honeymooned in Canada, we ended up with less Canadian change after a week than we did American change we’d brought in with us. When you can pay for actual things with the change in your pocket, you tend to do so.
By Bill Ruhsam, January 6, 2009 @ 8:48 am
That only works if you are someone who likes having change in your pocket. I despise change. Just ask Jenn. She is the recipient of all change that results from cash purposes by me (at least when she’s around). I hate hate hate having change in my pocket. I’m waiting for the day I can have a chip implanted in my thumb so I can do all my transactions electronically.
By Jim, January 6, 2009 @ 10:04 am
@Bill Ruhsam:
Small amounts of change don’t bother me, but when I get huge honkin’ amounts I know it’s time to visit the CoinStar or invest in vending machine futures at my office.
Maybe you should get a murse?
By Annie, January 6, 2009 @ 12:02 pm
@Jim: we found the same thing in terms of coin money in our time in Australia.
I for one, like coins. I’ve been known quite often to pay for my $5 lunch on campus all or in part with change (usually quarters, but sometimes mixed).
However, I don’t like the penny. It seems totally worthless because it takes too many to amass any real spending value (5 dimes way easier to carry over in a mass of change to the Dining Commons than 50 pennies are). Also, they have no vending machine value.
By Bill Ruhsam, January 6, 2009 @ 12:15 pm
Annie: But a bag of pennies makes a cheap club! Although if you want a nice clinkety club, you need to have pre-1982 pennies.
By Pat R., January 6, 2009 @ 3:42 pm
Not gonna lie, I’m a fan of change (although truth be told, if I had the opportunity, I wouldn’t have voted for it, sorry). Basically, I amass three separate collections: silver coinage in a plastic bank thingy I got at Shea; pennies in a jar (I unofficially collect them); and the cupholder in my console which is home to both. Every once in a while, I’ll filter out all the quarters and cash them in for “actual” money. And last time I did that, it garnered me a nice round $40, and I was like, “Yahtzee!!” Of course, afterwards my hands are rank with that coin-y smell that I despise so.
And I have one single Sacagawea dollar that I’m keeping forever. It’ll probably be a collectible someday (”remember that time fifty years ago when the US Mint circulated golden dollars, and they were popular for all of a week?”).
By Jim, January 6, 2009 @ 3:55 pm
@Pat R.: See, I spend my Sackies, when I get them (usually after buying mass-transit tickets with cash in NYC at a vending machine). I just like to mess with the cashiers that will be receiving the unpopular golden coins.
By Annie, January 6, 2009 @ 6:44 pm
@Jim and @Pat R: I used to get Sackies all the time when buying postage from the vending machines. I had fun spending them and messing with cashiers’ minds.
Additionally, there were a few Coke machines around the LCs on SUNY’s campus that would accept dollar coins.
By Bill Ruhsam, January 8, 2009 @ 10:42 am
Aha! Argentina hates change, too!
http://www.gadling.com/2009/01/08/wheres-all-the-change-in-argentina/
By Jim, January 8, 2009 @ 1:08 pm
@Bill Ruhsam:
Ha! Actually, Slate had an article on the Argentinian change shortage about a month ago. It’s quite a fascinating read:
Yes, We Have No Monedas!