While my thoughts usually concern my work day, sometimes my brain seems to take me on random flights of fancy during these half-hour scenic voyages along the Otago Peninsula.
For some reason, known only to the random biochemical connections that make us human, I started to think about the Earth’s direction of travel as it orbits the sun. As my battery-powered vehicle slowly clambered over the towering summit of a Mac Bay sleeping policeman, I wondered if there was an easy way to visualise Earth’s path through space. Literally, when you scan the sky, can you see where Earth is going, and where it has been?
Not surprisingly, I wasn’t the first person to think about this problem. Back in 1893, a rather fascinating American astronomer Thomas Jefferson Jackson See wrote an article about this very subject in volume 1 of the journal Popular Astronomy.
With the title "The Apex of the Earth’s Way", See described how, beginning in January, the apex of the Earth’s way, or Earth’s direction of travel, for the 12 months of the year is situated successively in the constellations Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, Pisces, Aries, Taurus, Cancer and Leo.
But it turns out, even if you don’t know your constellations, there’s an even easier way to "see" the apex of Earth’s way. Very roughly speaking, when the moon is in the first quarter phase, and you look towards it, you are looking in Earth’s rear-view mirror. And when you look towards the last quarter moon, you are looking in Earth’s direction of travel around the sun.
Tomorrow, the moon reaches last quarter phase. If you look towards it tomorrow morning you are looking in Earth’s direction of travel. How cool is that!
