October 16, 2018

Dating Artemis: An Astronomical Sci-Fi Mystery Solved?

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I love it when a hard science fiction book presents an astronomical mystery.

I came across just such a mystery reading Artemis, the latest science fiction novel out late last year from Andy Weir.

Artemis presents the story of Jasmine Bashara, a young girl trying to make her way in the first settlement on the Moon. Artemis is a thriving town, built around Earth tourism at the Apollo 11 Sea of Tranquility landing site.

We won’t introduce any spoilers here; suffice to say, if you like some hard science blended into your fiction, you’ll love Artemis. Like The Martian, Artemis also seems to be near-future science fiction, both culturally and technologically. We say “near” as in something that’s plausible over the next half-century or so. Also like The Martian, Artemis doesn’t peg the exact date when the events transpire… or does it? As an amateur astronomer and avid sky watcher, I noticed a few clues that just might pin down the exact future date of the tale.

Dating the Martian

Weir puts lots of research into his novels. With The Martian, he states that if you can work out the Hohmann transfer windows between the Earth and Mars needed for the Ares III mission to rescue and return Mark Watney back to Earth, then you could pin down the date in the 2030s when the events in The Martian transpired.

Is there a similar puzzle in Artemis? Well, I think there could be, based on you key celestial sights mentioned in the book.

Artemis runs on Kenya Time, as missions headed to the Moon depart from the equatorial country, taking advantage of its maximum rotational boost eastward and its favorable laws encouraging space companies to set up shop there. Kenya Time is Universal Time, +3 hours.

The most conspicuous objects in the sky as seen from the Apollo 11 landing site are the Sun and the Earth. “Daytime” on the Moon lasts about two weeks from sunrise to sunset… but the Moon is locked with one hemisphere turned perpetually Earthward, so the Earth would never set. Instead, Earth would go through phases like the Moon does as seen from the Earth, as it slowly circles a spot high in the sky due to the rocking nutation and libration motion of the Moon.

Earthrise as seen from Apollo 8 in orbit around the Moon. Credit: NASA

The phases you see from the surface of the Moon, however, are opposite to what you see on the Earth. This means when the Moon is Full from the Earth, Earth is at New as seen from the Moon. Likewise, waxing versus waning phases are reversed.

Artemis gets these phases right where it makes mention of them. On their own, however, one cycle of phases is pretty much like another… even making mention of something like an eclipse wouldn’t really pin the date down, as several lunar and solar eclipses happen, every year.

We get a possible lead, however, from the following passage when the protagonist checks her Earth-phase watch:

”Lene checked her wristwatch. ‘Ten thirteen a.m…and there’s currently a half-Earth, by the way. It’s waxing.’”

Now, that’s a little more specific… converting 10:13 AM Kenya Time to 7:13 Universal Time we just need to reverse the phase, and find when there’s a waning Last Quarter (half) Moon seen from the Earth around the same time.

Combing through the Astro-Pixels listing of Moon phases for the 21st century for Last Quarter Moons that will fall on 7:13 UT plus or minus one minute , I came up with the following possibilities:

August 30th, 2021 (it’s not likely that there’ll be a lunar outpost in just over three years!)

August 9th, 2099 (more likely).

Earth on August 9th, 2099 as seen from the surface of the Moon. Credit: Stellarium.

Of course, a few caveats are in order. Phases such as New, Full and Quarter are only instants in time. You could look up at the Moon (or the Earth, from the surface of the Moon) several hours one either side of Quarter phase and it would still appear pretty much half-illuminated. I own a Casio watch that shows the current phase of the Moon, for example… but it would be hard to pin down the exact moment of the Full or Last Quarter Moon with just the watch display alone.

Our very own “Moon phase watch…” photo by author.

Is the passage a true “tell” planted by the author? Maybe, maybe not. There are other methods the author could’ve used that are even more exact. Transits of Mercury and Venus across the face of the Sun, for example, are also visible from the surface of the Moon. On November 12th, 2190, for example, Mercury will transit the Sun, just hours from a solar eclipse… and if you’re visiting the Apollo landing site on November 13th, 2236, you can see Mercury transit the face of the Sun, during an eclipse:

Perhaps, future celestial phenomena will make their way into an Artemis sequel?

Read more original hard science-fueled tales by Dave Dickinson.