On horses, mental models, and 100-year old metaphors.
Michaela with my friend Katie’s horse, Brazil, at a dressage show on Whidbey Island, WA. Photo by Callie Neylan, 2006.
I don’t know if I ever told you this, but I love horses. Growing up in Colorado, you’d think I was around them a lot. Well, I was, but not as much as I would have liked. I’ve never owned a horse, but I always knew someone who had one or two, so I’ve ridden them more than a few times. And of course, the air always smelled like horses where I lived. Yellow like hay, green like grass, blue like 350 days of sun, and brown like a smooth leather patina or peaty dirt, whichever you prefer.
Close your eyes and take a sniff. Can you smell it? If you can’t, that’s a shame. Everyone should know what Colorado smells like, even if just briefly.
If I were ever to go back to the Centennial State, I think I would get a horse or two and spend the rest of my life outdoors in saddles, blue jeans, sunblock and skis. A mile or two high in the back pocket of happiness.
Speaking of which, did you see the movie Buck? If you haven’t and you love horses, too, you should. Horses really are beautiful, amazing, sensitive creatures who’ve evolved with man, just like dogs. We’ve shaped their evolution as they’ve shaped ours.
Think about their influence on transportation design, inspired mostly by the non-romantic reality of horses in our streets every day. And specifically regarding our mental models of power. It’s been over a hundred years since Henry Ford introduced the Model T, and yet, we still describe the power of engines in terms of what horses can do. When you stop to think about that, isn’t that kind of astounding? Will and I were talking about this the other night and I wondered out loud about the history of horsepower, so I came home, did a little research, and came upon this:
Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you’d have expended one horsepower-minute of energy.
Even more interesting is how the definition came to be. It was originated by James Watt, (1736-1819) the inventor of the steam engine and the man whose name has been immortalized by the definition of Watt as a unit of power. The next time you complain about the landlord using only 20 watt light bulbs in the hall, you are honoring the same man.
To help sell his steam engines, Watt needed a way of rating their capabilities. The engines were replacing horses, the usual source of industrial power of the day. The typical horse, attached to a mill that grinded corn or cut wood, walked a 24 foot diameter (about 75.4 feet circumference) circle. Watt calculated that the horse pulled with a force of 180 pounds, although how he came up with the figure is not known. Watt observed that a horse typically made 144 trips around the circle in an hour, or about 2.4 per minute. This meant that the horse traveled at a speed of 180.96 feet per minute. Watt rounded off the speed to 181 feet per minute and multiplied that by the 180 pounds of force the horse pulled (181 x 180) and came up with 32,580 ft.-lbs./minute. That was rounded off to 33,000 ft.-lbs./minute, the figure we use today.
Maybe part of why we hold onto this nostalgic metaphor is because it allows us to keep the romantic part of our national story with horses alive, while conveniently forgetting the part about ankle-deep horse manure and equine corpses all over the city. It makes me think of interfaces and metaphors: what metaphors ubiquitous today will still be around 100 years from now? What are the romantic parts that will survive? What new ones will exist? I think I’ll go celebrate Bastille Day now and chew on that for a while….