I'm still working on stories at sea and trying to learn more weird stuff about low-tech navigation. I decided to take some inspiration from the animal kingdom instead of limiting myself to ancient sailing tricks, and I'm glad I did. I was not expecting arctic terns and elephants to have similar voice tricks...
- Prehistoric sailors used cues like patterns in the currents and clouds to find land when exploring the open seas. They also followed birds.
- A Hawaiian star compass has 32 equidistant directional points, which results in 28 compass directions between the 4 cardinal points.
- When stars rise and set, they move about 1 degree into the sky every 4 minutes, although the angles they rise and set at change with latitude.
- Stars are only available for navigating by about 20% of the time. The rest of the time they're hidden by daylight and cloud cover.
- Changes in ocean currents — in the form of waves and swells — could signal the presence of islands and atolls, which helped early wayfinders find land when traveling the open sea.
In his (excellent) book Beyond the Blue Horizon, Brian Fagan describes how early sailors used myths, legends, stories and vivid names to help them navigate. Telling stories about distinctive geographical features helped landmarks stay memorable — which is critically important when traveling across vast landscapes with no opportunity to ask for directions.
Sailors still do this.
When my uncle taught me to navigate the Chesapeake Bay based on landmarks, he always called the local lighthouse "Rocket." It was even programmed into his GPS that way, although that's not it's name.
Seabirds like pelicans and terns may use infrasound to help them navigate over open water. Infrasound is sound so low in frequency that humans basically can't hear it, sort of like what elephants use to communicate over distances.
It wasn't until 2012 that we figured out how elephants make such low sounds — basically the same humans make sounds, with no special mechanisms (like the one cats use to purr, for example).
Infrasound offers a useful cue to seabirds because it works over long distances when, for example, land is not visible, scents on the wind aren't distinguishable, and there is too much cloud cover to see the stars.
There's an old saying, "red sky at night, sailor's delight. Red sky at morning, sailors take warning." It has to do with how solar radiation scatters at different angles depending on air pressure.
In mid-latitude regions (i.e. not polar or equatorial areas), the jet stream pushes air from west to east, which means that storms can be predicated. Low-pressure systems coming from the west usually bring storms with them. If they're coming from the east, it usually means the storm has passed.
Reversing the trick based on knowledge of local storms makes figuring out which way is north easier, too.
Scientists recently (within the last year) confirmed that sharks can navigate by sensing directionality and fluctuations in the electromagnetic field that surrounds the planet. They basically stuck some small migratory sharks into a pool and faked a magnetic field that mirrored different sites around the world. The sharks kept trying to swim back to their birth areas to breed, like sea turtles.
Sea turtles, stingrays, mud snails, tuna, dolphins, mole rats, honey bees, and other animals find their way using similar methods.
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