The Art of Science: Sticks and Swells

Marshall Islands Stick Chart, mid-19th century, Cambridge University Library
Marshall Islands Stick Chart, mid-19th century, Cambridge University Library

When I came across a photo of a Marshall Islands stick chart on Tumblr, I had no idea that it was anything other than an elegant piece of modern art. I was very surprised to discover that the stick chart was an important piece of navigational equipment that was in active use for thousands of years.

The Marshall Islands are a group of over a thousand small islands in the northern Pacific, which were settled in the second millennium BC. Stick charts were an ingenious way to navigate among the islands by canoe. The charts, made from coconut fronds tied together in an open framework, depicted major ocean swell patterns and the ways the islands disrupted those patterns. Shells were sometimes tied to the framework to represent the position of islands. Reading and interpreting the charts was a crucial skill handed down through generations.

The Marshallese continued to use canoes and stick charts for navigation until the mid-20th century, when they gradually switched to motorboats and electronic navigation systems. The charts survive not only as history, but as an art form deeply imbued with the values of an ancient, ocean-centric culture.

You carry your GPS with you

NDrive_GPS

Somehow, when you get out of bed in the middle of the night, you manage to remember where the end of the bed is, how far it is to the bathroom and where the light switch is. You have developed a complex spatial memory of your house, and our brains are filled with countless other spatial maps (maybe some of us have fewer….cough, cough). How exactly does your brain encode this specific spatial information?

It turns out that is it using cells called grid cells, which work much like their name suggests. These neurons are spread out in a grid pattern in your brain and will generate an electrical spike in a pattern related to the direction you are moving. While this has been known about rats, mice and bats it has only recently been confirmed in humans. While fMRI experiments have suggested the existence of such cells, the only way to confirm that individual cells are spiking in response to a directional task is to make electrical recordings from them.

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