DARK SKY HAPPENINGS - December 2020

Ahoy, Matey! Land Ho! Polly want a Cracker?
By Mila Dunbar-Irwin, MSc

These nautical phrases have been established in the popular lexicon since the age of sea-faring sailors – whether pirates, traders, or explorers. It wouldn’t be too much of a stretch to say that exploration by sailing ship gave rise to the world as we know it; the trading of goods, culture, people, plants, animals, and political systems across the oceans indelibly changed the world and gave rise to whole genres of literature, film, and art.

Did you ever wonder how those early sailors got around? How they navigated vast expanses of oceans without landmarks of any kind?

The answer is: the stars!
There is speculation that as early as the 14th century, Polynesian settlers arrived on Aotearoa (also known as New Zealand) via canoes which they had paddled across open ocean navigating by the stars. Even before that, the ancient Minoans from Crete were using the stars to navigate 2000 years BCE. Like many of our animal cousins, humans have been looking up at the night skies and using the stars to get around for as long as we’ve been humans.

If you’ve ever been curious how it works, you can just ask a recent graduate of the US Coast Guard Academy, where celestial navigation is still a required course to graduate. Unable to be intercepted or jammed - like a GPS signal – not needing electricity of any kind, and able to be used anywhere in the world, celestial navigation is still considered the safest and most secure form of navigation to date. Long distance yachtsmen and intercontinental ballistic missiles are other current users of this ancient technology.

The way modern celestial navigation, invented in 1837 by Thomas Hubbard Sumner, works is this: each of 58 navigational stars, plus the moon and planets, has known coordinates published in an almanac for any given year. Angles between three of these bodies and the horizon are taken with a sextant, computations are then performed known as sight reduction, also involving an accurate reading of the time, and then the resulting measurement is used to plot a line of position on the navigational chart for the area. These three lines of position result in a fairly accurate triangulation of your spot on the map. Voila!

Or, to get yourself started with backyard celestial navigation, you can go outside, find Polaris, our north star, at the end of the big dipper, and set off into the night. Just remember to keep it behind you on your way back!

MOON HAPPENINGS
Dec 21 - First Quarter at 4:41 pm
Dec 29 - Full Moon at 8:28 pm