Finding your way
You can truly appreciate how far we've come in technology when you realize that sailors once measured speed by throwing something overboard and seeing how long the ship took to pass it.That's the first thing you learn at the "Art & Evolution of Navigation" exhibit at the Museum of American Heritage in Palo Alto. Interesting. I may try it on the freeway.
Then there's the ever-popular “navigation by echo,” illustrated by a wooden ear trumpet you listened to in the fog while letting loose a foghorn. “Elapsed time between the blast and the echo gave the approximate distance from the reflection point,” says the exhibit.
It’s a fun little exhibit, especially educational for today’s whippersnappers who think the world revolves around those newfangled Google maps, which allow you to see the roof of your favorite McDonald's in Russia. Throw them a cross-staff and see if they can find the latitude of Honolulu using only a fake North Star on the wall.
There’s plenty of more modern stuff, too, including an aircraft magnetic compass, radio-based direction finders and info about how the Mars Rover finds its way around.
Should I give you the address of the museum, or do you want to find it yourself? Awright, awright: it’s at 351 Homer Ave. Open hours are 11 a.m. to 4 p.m. Friday through Sunday.
Pictured above: A revolution counter that counts the number of ship propeller revolutions, allowing you to estimate the distance the ship has traveled in a given time. Below: An old globe in the exhibit. Photos by Ron Evans.
posted by Rebecca at
2:29 PM
3 Comments:
At last, someone who explained why sailboat speed is measured in "knots" instead of miles.
By
Marina Profundo, at 10:52 AM
Finding nautical speed using the olde ways and finding one's way through fog resonates with me.
In 1996, I traveled with 10 other people on a 30-foot sailboat 200 miles up and back down the coast of Maine to the Canadian border (or down and back up the coast, as the locals like to say).
The boat had two sails and eight oars, with one person per oar.
We measured speed by having someone toss a piece of food off the bow and measuring the time it took to pass the stern. The formula probably had something to do with the boat's length; I don't remember. But if we were going slower than two knots, we had to start rowing.
That you don't forget. At the end of the 24-day voyage, our hands were calloused and hard.
We were caught in the fog several times. It's quite an experience when you have no electronic navigation aids and the tide is changing and you don't know where you are relative to the land. It feels like anything could happen.
I remember seeing a point of land and spontaneously yelling "Land's end." It was that engaging.
One time we were on a rather crowded inland waterway and we could hear the fog horn of an approaching vessel, probably a Coast Guard cutter, but we had no idea where it was.
We had a foil reflector at the top of the main mast to alert ships' radars of our presence, but the skipper was nervous. He used his little emergency radio on the standard frequency to call the cutter but got no response. Why? They were probably looking for drug smugglers, he said. On the Maine coast? Yes, apparently.
Fog distorts distance; we were hearing this horn for maybe 10 minutes, always getting louder. We strained our eyes and ears, we heard a bow wave cutting through the water but saw nothing.
You can imagine the anxiety.
Finally, the fog lifted a bit and we saw the cutter about 50 feet away. They gave us no sign of recognition as they passed.
Dave Boyce
Menlo Park, CA
By
Dave Boyce, at 11:00 AM
One of my favorite writers, Samuel Clemens, of course wrote under the pen name of Mark Twain, which in his time refered to a way to navigate a river channel. "Mark Twain!" was called out when a rock tied to a rope and dropped into the water measured two fathoms (12 feet), a safe depth for steamboats.
By
Ron Evans, at 11:16 AM
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