August 24, 2011 | 2
Okay, so we all had a swell time: the floor starts jiggling like a jello-mold, and those of us who didn’t run outside ran to Twitter, and it was on. Within seconds we were linking to the USGS site, the sites for the impenetrable Richter Scale and the simple, purely descriptive Modified Mercalli Scale (“III. Vibrations similar to the passing of a truck”), to the USGS “Did you feel it?” site, which yields a marvelous map showing Mercalli Scale responses of those who had felt it, showing by color how the perception of the quake’s intensity diminishes the further you get from the epicenter.
Then we even started flinging references to the awesome xkcd cartoon strip showing how Tweets outpace seismic waves, which we were at that moment proving to ourselves anyway. With links to ways to connect sensors to our own computers, thus joining a worldwide network of citizen scientists, we quickly moved on to congratulating ourselves on how our modern, connected, instrument-centric method of observation makes science so awesome. You can look up your own response on the data set!
So naturally I got to thinking about how, well, nuh-unh. Or at least about how little has changed.
For one thing, earlier in the day I read this excellent post from this very site about whether growing hurricane intensity might not mean we need to add a new, higher level — level 6! — to the Saffir-Simpson scale of hurricane force. That scale, which combines purely observational descriptions (“failure of aluminum, screened-in swimming pool enclosures can occur”) with wind speeds (74-95 mph) corresponds much more strongly with the Mercalli earthquake scale than with the Richter scale. That is, it’s about what’s happening, not about some abstract number. And you use it by looking around, not by staring at a screen or a meter. Both of those scales have as their progenitors the Beaufort scale of wind force, the mother of all observational scales (“5. Small trees in leaf begin to sway”), which is as lovely as a piece of found poetry as it is useful as an observational scale and has been around since the early 1800s.
I tell you all that because none of this is new. Yes, it’s nice to see that instantly updated USGS map, and to have Twitter to time stamp our observations and slap locations on them. But in the mid-1800s, the Manual of Scientific Enquiry, a sort of scientific handbook designed for naval officers and “travelers in general” — that is, people “of merely good intelligence and fair acquirement” – did exactly the same thing: using nothing more complex than a grandfather clock.
The word “scientist” was still pretty new in those days, and you didn’t need a degree — if you did sciencey stuff, you were one. So the Manual was a way to get the word out about as much as possible to as many people as possible. There are chapters about meteorology and botany and zoology and hydrography and so on. But germane to our shared earthquake experience was the section on earthquakes, in which the writer comes up with a brilliant way to measure the direction and speed of seismic waves.
Here’s how it worked. First, you drilled holes in the sides of the pendulum casing of your grandfather clock. It had to be a good clock, and it had to be set daily to Greenwich Mean Time. Then you attached extremely light cords to the pendulum, running out the holes. Then you attached the cords to a log, balanced on end. Comes an earthquake, and the log will fall, pulling the cords and stopping the pendulum. Then all the seismologists have to do is find out at exactly what time the various clocks stopped and plot the points on a map. You’ll see the epicenter at the earliest time, and later times radiating outwards until you get to the point where the wave was no longer strong enough to knock over the log. Want more detail about force? Set up a series of dowels in different sizes and see which ones get knocked over.
It’s hard, of course, not to wonder how the spouses felt when they came home: “The clock! What on earth have you done!” “Why, not to worry — it’s an earthquake app, dear.”
Anyhow. I guess the point of this is little more than hey, that was fun. Something happened, and we all got to participate in understanding it and providing data so that scientists could help us explain it to ourselves. But I also wanted to point out that we’ve been doing that for a long time, and though we get the pretty maps faster these days, the same type of people were making the same type of maps for the same purposes long before we ever got here. And that there’s a lot to be said for using, say, the Mercalli Scale — which lets you judge intensity by observing what fell off your shelves — instead of the Richter Scale, which forces you to try to explain logarithms to your children just when they were getting interested in earthquakes.
And I suppose that people have been doing science with what they had around the house for as long as they’ve been doing science. If anybody tries the grandfather clock earthquake method, please send me a picture and tell me how it works.
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