#107 July 1997
Section 18.104.22.168.107.of the Artemis Data Book
Earth: Color Medley Calendar in the Moon's Nearside Sky
by Peter Kokh
[Astronaut quotes below were passed on to us by Cynthia Griffin, Space Research Associates, and are from remarks they made to an audience of military personnel and civilians at the May '97 National Museum of Naval Aviation's annual symposium.]
In "Seven Wonders of the Moon" [MMM #69, OCT. '93, p. 8] the view of Earth, hanging there perpetually in the Nearside Sky was listed as one of them. We billed it as "an apparition in the lunar nearside heavens with 3 1/2 times the breadth, blocking out 13 times as much of the starry skies, and shining with 60 times as much glaring brilliance as does the Moon as seen from Earth &emdash; all in a spinning ever changing marbleized riot of blues, greens, browns, and whites."
Earth as Clock and Calendar
Earth-in-the sky will offer future Lunans endless fascination as well as a psychological anchor (for better of for worse) for their morale. More on these benefits later. First we want to outline how Earth offers clues to (a) the time of the lunar month or "sunth" as we've more aptly named it, (b) the time of [calendar] day or date, and (c) the time of the year.
TIME OF "SUNTH": Earth-in-the-lunar-sky goes through the same series of sunlit, night-darkened phases as does the Moon in our skies &emdash; with some spectacular differences. "New Earth" when eclipsing the Sun during what the Earthbound interpret as a Lunar Eclipse will appear as a dark circle in the heavens crowned with the fiery ring of the sunset-sunrise line as sunlight scatters in the dust of Earth's atmosphere. At this and other times, the night-darkened portion of the globe has become in this century increasingly "star-studded" with the city lights of burgeoning urban areas as well as oil and gas field burnoffs of "waste" natural gas and hydrogen. Meanwhile the frequent reflection of the Sun off ocean and ice accentuates the sunlit portions.
The point, not to wander in wonder, is that New Earth corresponds to Full Moon (the entire Nearside hemisphere in dayspan); First Crescent Earth to the waning Moon (nightspan advancing from the east over Mare Crisium etc.); First Quarter or "Half Earth" to nightspan having advanced to the central meridian of Nearside, dayspan advancing to the central meridian of Farside. And so on. In other words, as seen from each other's surfaces, the phases of the Earth and of the Moon are opposite.
In practical terms, the lunar nearsider will be able to deduce from the Earth's "phase" what is his local "time of the sunth": just after local daybreak, dayspan morning, dayspan afternoon, etc. Of course this will differ according to where the viewer is on the nearside (i.e. at which meridian).
TIME OF DAY (DATE): While the Moon keeps the same face turned toward Earth at all times, Earth-in-the-Moon's-sky turns on its axis once every 24 hours. Whether the viewer sees the Americas, the Atlantic, Europe & Africa, Asia and the Indian Ocean, or the Pacific as facing him, will tell him what portion of the local 24 hour date it is (distinguishing date form the 14.75 date long dayspan and the 29.53 date long sunth). Depending on how Lunans set up their local calendar and time reckoning rubrics (that is if they do not import unchanged the time reckoning system of Earth), the above concordance may be fixed or it may precess by an hour every 40-41 days if Lunan calendar is set up as I've suggested (so that there are exactly 29.5 dates per sunth, rather than 29.5306).
TIME OF YEAR (SEASON): How the Earth's axis tilts with relation to the Lunan observer at different times of the sunth, will tell him the time of year. The tilt will shift full cycle through the sunth (sequence of phases). If at 1st Half Earth, the north pole tilts toward the right (towards the Sun) it is northern summer, southern winter Ditto at 2nd Half Earth if the tilt is to the left, at New Earth if it is away from the observer, and at Full Earth if it is towards the observer, and so on.
Accompanying the tilt will be confirming visual clues: snow cover in higher Northern latitudes or in higher Southern latitudes corresponding to that hemisphere's winter, the other hemisphere's summer, and so on. Yellow-oranges replacing green shades in temperate zone forests will indicate Fall in that hemisphere, Spring in the other hemisphere. More seasoned observers will be able to recognize seasonal clues in between to give a better approximation.
On the ball Lunans will be able to look up at Earth and tell the time of day (date), a close approximation of the date of the sunth (month), and which sunth/month of the year it is &emdash; all at a glance. It is the spectacle of Earth, however, that will turn that glance into a lingering observation, the seer into a transfixed looker. While Earthbound students can patiently study an all but changeless Moon, lunar settlers and visitors looking up at Earth will have an unending drama of riveting kaleidoscopic change to admire and study. It will be a treat without the distraction of flora and fauna and weather in the foreground, a Van Goghish canvas of color under-statedly matted by black sky and gray regolith.
The first impression will be of ever changing cloud patterns; of hurricanes, cyclones, and typhoons; of storm fronts. Playing hide and seek with the shifting clouds will be the blues of the oceans and lakes and seas, the greens of grasslands and forests, the light tans of the deserts, and the glaring white of snow and ice. Beyond the day/night terminator, again playing hide and seek with the clouds, will be a light show extraordinaire: lightning and forest fires on the natural side, city lights and oil and gas burnoffs added by man. Different observers will see and watch for different things, each according to his/her own interests. Some will habitually count lightning strikes, jotting numbers in a log. Others will try to catch a glimpse of the light patch that locates their hometown lights or the lights of other towns, cities, and urban industrial archipelagoes.
Relatively few sets of elements will contribute to the never repeating sequence of Kaleidoscope treats. Not all the elements will appear with the same frequency: for example, the appearance and track of the approximately 60 mile wide Moon Shadow across the lit face of the Earth during what terrestrials experience as locally very rare Total Solar Eclipses. And the relatively glare-free conditions of solar eclipses (which we experience as eclipses of the Moon), many fainter nightside light glows may become visible to the practiced lunar observer.
"Mansign": Earth as an Inhabited World
That Earth is an inhabited world will be quite apparent. In the night portions of the observed face we will see the city lights, some unnaturally frequent forest fires, and the oil field gas burnoffs. In the sunlit portion of the Earthglobe we might see some agricultural patterns, and even detect portions of national borders betrayed by differing land use patterns on either side. We'll also see slow changes from advancing deforestation and desertification. Man-made reservoirs will catch the sunglint where once their was all-but-undetectable river valley. And we'll spot natural floods that are here and their 'controlled' by man-taken measures. All these signs will be studied acutely by those keenly interested in the great unplanned experiment of environmental "deterraforming", going on more or less continuously since the invention of slash-and-burn agriculture in Europe some eight thousand years ago.
For those fascinated by Earth's city lights and their identification, an amateur observing league may give out "Edison Certificates" to those who have correctly identified a representative selection of a hundred-some urban concentrations - much like the Messier Certificate Program in which backyard astronomers seek to identify star clusters and nebula on an early and popular list of the brightest such objects. Advanced observers will be on the watch for blackouts, major fires, night launch rocket booster burns as well as fiery nightside reentries.
For the Earthborn, night lights of homelands and hometowns and spaceport points of departure will hold special interest. For native born Lunans, night objects sought out will include a less predictable list of various places they've each heard and read about, and which have fired their imagination.
Naked eye observation of Earth
Full Earth illuminates moonscapes with sixty-some times as much brilliance as Full Moon brightens earthscapes. But without a dust and water vapor laden atmosphere on the Moon, earthshine shadows will be inky black and impenetrable. A happy result is that starlight is not drowned out.
Yet not all lunar settlers and visitors will be able to appreciate Earth-in-the-sky with equal ease. To paraphrase the opening sentence in Caesar's report on the Gallic Wars, "All the Moon can be divided into four parts".
In the central portions of Nearside, Earth is either directly overhead or at a very uncomfortably high angle above the horizon. We might nickname this central area the Crooknecks. It includes most of Mare Imbrium, Mare Nectaris, Mare Serenitatis, Mare Tranquilitatis, Mare Nectaris, Mare Vaporum, etc.
The Postcardlands are the peripheral stretches of nearside, regions in which the Earth hovers perpetually a comfortable 5-40° above the horizon. Adjacent to these, straddling the "limb" of the lunar globe which forever keeps the same side turned towards Earth are the Peek-a-boos. As the Moon's axis is not perpendicular to its orbit around Earth and because that orbit is somewhat eccentric and the Moon travels faster when nearer Earth and slower when further away, all the while rotating at a fixed rate, about 7° to either side of the 90° East and 90° West lines are alternately turned towards Earth and away from Earth, psychologically annexing about 9% of "Farside" to Nearside.
Together the above three regions cover 59% of the Moonglobe. The remaining 41% might be dubbed the Obliviside, the Farside heartland from which Earth is never visible - and as the old saying goes, "out of sight, out of mind."
Special Observing Equipment
Special equipment will not, without signal relay, make it possible for deep Farsiders to observe the Earth. But in Greater Nearside, if we might call it that, many of those enthralled by the sight of Earth will be motivated to go beyond Earth-facing picture window portholes in their shielded abodes.
Oculars and binoculars will be among the simplest terrascopic assists, along with large Fresnel lenses or projection lenses in front of windows, much as late 40s/early 50s small screen TVs used similar fore screens to magnify the view. Special amateur optical telescopes designed with the aperture above the surface, but the observer eyepiece optics within the pressurized habitat for direct shirtsleeve observation will be popular with purists.
But for others, HDTV monitors, interactively zooming in on selected portions of the Earthglobe, will provide even better views. There might even be a dedicated fully interactive yet live Earth View Channel offering not only spectacular live detail, but also multi-spectral false color enhanced imaging that cues in on ultraviolet, infrared and other cues in the more complete light spectrum. various interactive programs may search on demand for lightning flashes, pick out keyed in cities or other locations, even overprint city names of areas on which the viewer has focused in. Instead of the view from the Moon, auxiliary channels could give the view from LEO and GEO satellites, or even from future flank observation outposts in L4 and L5.
As on Earth, some avid observers will be heavily into photography, others into interpretive drawings, and yet others into raw and immediate unfiltered live observation. Yet glare reducers and variable masks for night side viewing will be standard (and the automatic default setting on TV).
Earthsight as an Umbilical Fix
The riveting sight of Earth will be the chief anchor with 'reality' and with the heritage of their individual pasts for the early Lunan pioneers.
--------------------------------------------------One can argue if this is good or bad. Deep Farsiders may tease Nearsiders about their mommy-fixation to Old Earth, boasting of a keener, deeper openness to the Universe at large, and of a greater space-hardiness that results. We'll see. <MMM>
``Landing on the Moon was not nearly as over-powering and as memorable as just going to the Moon and looking back at Earth. We went to explore the Moon, and in fact discovered the Earth."Eugene Cernan.--------------------------------------------------
Looking out the Apollo Module porthole from out around the Moon, Apollo 8 and 13 astronaut James A. Lovell, looking back at Earth, was able to block it out with his thumb. Later he recounted, "Everything that I ever knew - my life, my loved ones, the Navy - everything, the whole world was behind my thumb."
Contents of this issue of Moon Miners' Manifesto