June 7, 2019--Once Again: The Rhumb Line

A number of people asked me to repost this. It first appeared July 27, 2016. The "George" is George Lindberg. He's always good for a story.

It was a hot morning and George took a break from mowing our lawn.

"I hear from your missus that you're looking for a new place to have lunch on Wednesday."

"Yes, a cousin is going to be in the area. In Rockland."

"I know you like the Slipway in Thomaston. The same owner now has a place on the harbor in Camden, the Rhumb Line."

"That's exciting," I said, "He had one of our favorite places in Port Clyde. Until Linda Bean of the LL family bought the property. He couldn't stand her because of her homophobic politics and refused to remain as chef. That's when he opened the place in Thomaston."

"The one in Port Clyde was called the Dip Net."

"In addition to being such a good restauranteur," I said, "he comes up with great names for his places."

"What do you think about Rhumb Line?" George asked.

"We haven't been there yet," Rona said.

"I mean the name."

"I know what a dip net is--a long-handled net used to land fish--and a slipway is a boat launching ramp. But a rhumb line? That's a new one for me. It sounds nautical."

"It's a navigation term," George said, "If you don't know what it is I think you'll like it."

"I'm eager to hear."

He let go of his lawnmower and with a sweeping gesture, using both hands, created in the air the shape of a large sphere. "Make believe this is the earth," he said, "In three dimensions."

"I got you. I loved solid geometry in high school. Especially how to think about and understand how lines on a solid three-dimensional globe work. Arcs and such."

"Exactly. So if you, for example, head east from here across the Atlantic and don't change course--in effect, go straight--the shortest distance from point to point is not a straight line, as it is in two-dimensional plain geometry, but an arc, a circle. Thus ships or airplanes follow the Great Circle Route to get to England most directly."

"And a rhumb line?" I asked.

"I'm getting to it." George likes to take his time when explaining concepts to be sure you're following him. He's really good at this. Particularly if the concept is complex or full of ambiguity. His favorite type. He also likes telling stories of all sorts. The shaggier the better.

And so, again with a gesture, maintaining the outline of the globe with one hand while with the other, where the Equator would be, he traced a spiral in the air, up from the Equator toward the North Pole.

"A rhumb line is a line on a globe that as it moves forward crosses all lines of longitudes at the same angle. That's the key--the same angle. Longitude, as you know, being the way on a globe that we map north-south slices of space and location."

"I think I'm beginning to get it," I said, "To trace a great circle on a sphere one moves along in a three-dimensional arced line, not changing course because the distance between lines of latitude are constant."

"Exactly."

"But with a rhumb line, to cross longitudes at the same angle one has to constantly change one's course."

"And thus a spiral is traced on the globe because as you head north--or south for that matter--as one approaches a pole the separation between the lines of longitude get narrower and narrower. If you will, compressed closer and closer together so it's necessary to constantly adjust your heading."

"And?" I said.

"And what?" George said.

"Whenever you get into these kind of things you always have another meaning or two to offer."

"Me?" he said with a shrug, trying to hide a smile.

"Please proceed."

"I know how you like to go round in circles. I mean," he quickly added, "not in a bad way, but metaphorically to see what you might stumble onto that's interesting."


"Could be true," I conceded. "And so?"

"With great circles and now rhumb lines you have more circles and spirals within which to go round." George winked.

I tried to get us back to basics, asking, "But is it a good restaurant?" I thought I had cleverly circled around to where we began.

He smiled and, ignoring me, said, "According to the theory, no matter what course you set we all end at the same place."

As I pondered that, he said, "But be sure not to forget to order the fried oysters."