Navigation and Planetary Motion
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In which we touch on some of the theories of the Behaviour of Planets, including which elements may concern Navigators, and which may safely be ignored.
The Behaviour of the Planets
Ever since the discovery that Alusia was a globe, and that the Sun was merely a star in the heavens, a debate has raged as to whether Alusia circles the Sun, or the Sun circles Alusia, and some even argue whether they move in circles at all. A similar debate exists over the movement of the Moon, for although all sides agree that the Moon does circle Alusia, some say it travels around 27 times in a month, and others that it travels in retrograde fashion once a month. For the practical Navigator these discussions matter not, but the principles and explanations given by each side shed light on the behaviour of the Moon and Sun, and the tables and rules of thumb presented in this and similar works each assume a certain behaviour of the Planets.
Herein I will describe the various theories of which I am familiar, along with their reasons for and against, and some of their consequences. And I will also show how the principles upon which the tables of this book are built will work with any or all of the more reasonable theories, showing that the arguments indeed have their proper place with the Philosopher and Astrologer, and not the practical Mariner.
The Geocentric Model
The first and most obvious explanation is that Alusia is the still centre, about which the Moon, the Sun, the moveable planets and even the fixed stars of the firmament rotate. It is usually explained as a series of concentric spheres, one for each heavenly body, ordered as Moon, Ariel, Freya, Sun, Thunor, Wotan, Hela, (Merlyn?), the starry Heavens, and the outermost being the firmament. This theory is most clearly backed by observation, for any person looking up at the sky at night sees all these bodies moving from East to West, at a similar rate. Now, that the Moon moves more slowly than the stars, circling only 27 times in 28 days, or that the sun moves more rapidly than the stars, making 364 turns when the stars make only 363, can be explained by the different celestial spheres upon which they rest move at slightly different rates. However, that the inner wanderers Ariel and Freya always stay close to the position of the sun, and vary both to and fro within that constraint, or that the outer wanderers Thunor, Wotan and Hela do vary in speed, and sometimes even move in retrograde, cannot be explained; nor can the waxing and waning of Thunor and to a lesser degree the other outer wanderers.
Furthermore, it is known that the seasons depend on the position and angle of the Sun, for in Summer the days are longer and the Sun higher in the sky, and in Winter the converse holds. But if the Sun went around Alusia, as it is observed clearly to be orbiting at an angle, when it is Summer in the Western and Northern Semi-Hemisphere, it would also be Summer in the Eastern and Southern Semi-Hemisphere, while being Winter in the Eastern and Northern, and the Western and Southern Semi-Hemispheres, and this is not true, the Seasons carrying only by which Hemisphere, being Northern or Southerm , you find yourself in. And, as we see that the Sun is almost 100 million miles away, for it to circle Alusia in one day, it would need to move at 25 million miles an hour, or nearly seven thousand miles per second. And all of the outer wanderers, the fixed Stars, and the firmament itself, each being outside the other, and all outside the Sun, must each be spinning at a greater rate than shown above. This seems unfeasibly fast, but we should suspend judgement hoping that other theories provide more reasonable figures.
The Heliocentric Model
The alternative explanation, being one often held by the ancients, and by many of the newer type of Philosopher, but always by the Church being steadfast in its search for the truth, is that the Sun is the still centre, with the wandered moving around it in order Ariel, Freya, Alusia, Thunor, Wotan, Hela, ?Merlyn?, and with the stars and the firmament also fixed. And the Moon rotates about Alusia, with some of the other Wanderers also having their own children, such as Fear & Terror which circle Thunor, and the sightings of regular small occlusions of Wotan and Hela being ascribed to similar child bodies circling the planets.
And now the different rates of movement can be explained as follows. First, Alusia is not fixed, but spins nearly a full circle on its Poles every 24 hours, and this accounts wholly for the visible movement of the stars, and for most of the rest of the movement, being a regular East-West movement of all celestial bodies. And the differences are explained by the movement of the other planets, being that the Moon moves in retrograde around Alusia every month, making it appear to circle 27 times for each 28 rotations of Alusia. And Alusia circles the Sun once every year, explaining the apparent movement of the Sun through the houses of the Zodiac throughout the year, as different star constellations lie behind or opposite the Sun as Alusia circles. And the movement of the Moon through the Zodiac every 26 days is due to its movement around Alusia 13 times in the year plus one addition circle due to Alusia's movement around the Sun, with 14 orbits in a year giving 26 days before the Moon appears in front fo the same stars again. And the inner Wanderers, ling between Alusia and the Sun, and making smaller circles of the Sun, will always appear to be close o the Sun, and make small circles so finish their circling in less time, while the outer Wanderers in lying beyond Alusia may seem to move rapidly when away from the Sun, and more slowly when closer, this being when they are in fast further from Alusia, but moving still at a constant speed.
And the Seasons are due to Alusia not sitting upright when spinning, but now favouring the North, and now the South, like the child's spinning top which it resembles as it spins itself, and arcs in a circle around the Sun, as any top does when spinning. And this ensures that the Seasons are the same for the Eastern and Western Hemispheres at any time, for the tilt is not a wobble of the Pole, but the whole world elegantly slanting over to an extent of perhaps 23 degrees, and in one half of the year it being the Northern side that is closer to the Sun, and in the other, the South. But arguments about the spinning of Alusia can be raised, for first why do we not fly off due to a rate of spin which at the Equator is over 1000 miles an hour, reducing to nothing at the Poles? And the usual answer given, which is that this is from the same reason as that the Antipodeans do not fall off, being on the underside of the world, seems at best question-begging and at worst malicious. And the rate of Alusia circling the Sun, while reduced from the Geocentric model by 364 times, is still 20 miles a second or nearly 70,000 miles per hour. The figures from this model, while smaller, are hardly more reasonable than the Geocentric Model. And yet the explanations of the planetary movement, although more complex initially, seem to better fit the variation in types of movement, and holds better to observation.
Epicycles
And close measurement of the Moon, the Sun, Freya, and Thunor and to a lesser degree the other wanderers being harder to observe carefully, shown that they do not move in equal arcs across the sky each sky, but hasten and slow, and some do appear to move backwards. And to explain this behaviour, the notion of epicircles has been expounded, this being that the celestial spheres move in regular and even rotation, but that smaller circles are attached to each sphere, on which the planets are fixed, and these epicircles, rotating at different rates in epicycles, can explain the variations. And the most precise predictions of the planets have up to 5 or perhaps 7 epicycles for a planet, each being a spinning plate on the rim of another spinning plate, and so forth, each moving in a perfect circle affixed to a larger spinning circle. And it seems to me to be an elegant explanation, except for the why of each planet sitting on so many spinning epicircles, and how they, being worlds like to Alusia, need all this construction and artifice, when Alusia, which seems not so different from them from the ground (I having stood on Thunor at least) is fixed and still. And the latter problem only arises when it is used with the Geocentric model and yet this is the model usually propounded by epicyclists.
Ellipses
And given the complexity of the epicyclic model of motion, it is not surprising that another theory has been proposed from time to time. And this theory is that the celestial bodies do not move in perfect circles, but in ellipses, these being circles extended somewhat in one direction by having two centres of rotation. And this shape is best demonstrated with two pins and a loop of string, for by placing the loop of string around the two pins, being fixed to a board close together, one may draw a shape with a pencil placed through the loop so as to keep it taut at all times, and by varying the placement of the pins, the circle or ellipse is broadened at will. Now the theory of ellipses has a number of problems, being first how the celestial spheres are replaced with these irregular oval shapes not being stable in rotation but prone to wobbling at any speed as a model will demonstrate, and second that it is less accurate than the epicycle model, although as accurate as perhaps any 2 epicircles could allow for. While epiellipses have been proposed by a few daring souls, and may allow for greater accuracy, this approach combines the weaknesses of both types of motion, and is liked by neither camp. And the first problem arises only when it is combined with the Geocentric model which requires far greater speeds, and may be why the Heliocentric model is preferred by Ellipists.
A Compromise Model
As stated above, no Mariner wishes to worry about whether Alusia is a spinning top, or if the Sun is moving too fast, or whether the planets circle one celestial body or another. And yet, to predict the movement of the Sun or the Moon, some model must be selected that is accurate enough, and yet is not opposed to any discovery, so that our tables and regiment need not be changed with every appointment of a new Head Astrologer at MMHS University. And the compromise model used in this and most Navigational Almanacs is as follows.
To someone on Alusia, the following observations always hold: That the Moon appears goes around Alusia 27 time every 28 days; that the Sun rises in the East, with a variation North or South according to the Seasons, and sets in the West, with a corresponding variation. That the Sun's declination varies smoothly between Summer and Winter by 23.5 degrees each way from the Equinoxes. That the Sun varies slightly in its Zenith time, not being exactly 24 hours after the last, and this variation is due to the addition of two smooth variations, one being an annual variation up and down by 15 minutes, and the other being a semi-annual variation up and down by a similar amount, the two never combing to more than 24 minutes of variation. That the Moon varies in a more radical manner, having first the pair of variations of the Sun, on a basis not of a year or a 28 day month, but the first variation being once per Anomalistic month, and the second variable being twice per Draconic month, with no variation at both the head and the tail of the Dragon, as explained in previous chapters. And the Anomalistic month is a little longer than the Sidereal Month (the 26 days it takes for the Moon to pass through the Zodiac), and the Draconic month is a little shorter than either. And that the tides are moved by the Moon, being a full Sea at the same point each day, excepting that you be inland on a large river at a Spring tide, as noted in a previous chapter, with neither model explaining why the tides move as they do, particularly how they circle around large islands in keeping with the movement of the Moon.
Geocentric Variations
And the annual variation of the Sun is due to the sum of the two epicircles of the Sun, one being a cycle completing every year, and one completing every half year, with each appearing to slow or hasten the Sun's movement in its true circular orbit. And the Anomalistic variation of the Moon is due to an epicycle of just over 26 days, and the semi-Draconic variation of the Moon is due to an epicycle of just under 13 days, both appears to slow or hasten the Moon's movement it its true circular orbit.
Heliocentric Variations
And the annual variation of the Sun is due to the elliptical orbit travelled by Alusia, with the Sun being at one of the pins or centres of the ellipse, so that sometimes Alusia is further from the Sun and so the Sun appears to move more slowly, as does any object at a greater distance. And the semi-annual variation of the Sun is due to the tilt of Alusia as it spins, for as Alusia tilts from the upright, the Sun appears further to the North or South, but also, due to the angle of the tilt, seemingly further to the East or West. And the Anomalistic variation of the Moon is due to the elliptical orbit of the Moon taking slightly longer to complete its ellipse than it takes to compete its orbit, as if the two pins were very slightly turning as well (turning but 7 times in 18 years). And the semi-Draconic variation of the Moon is due to Alusia's tilt combined with the the Moon's own orbital tilt of just over 5 degrees, with the Moon's tilt completing a cycle of wobbling around Alusia not at a smooth 26 days, but slightly faster at once per Draconic month.
Understanding the Variations
And no Navigator need understand the explanation of how the observations fit within either model, except to be able to agree with either school of Philosopher, and so escape mental or physical abuse from being caught on the wrong side of an academic debate, for which model best describes the Behaviour of the Planets is true is all of a muchness when you are at Sea. And the tables provided here work with all models, but the automatic tables are written with a Geocentric model using epicycles measured as a proportion of the true circle in the manner of ellipses, being the easiest way to describe the variation for the author, being a practical Navigator and Mariner and not fully conversant with the methods of Philosophers and Astrologers. And any theoretician who is offended by my dismissal of the relevance of their field, please bear in mind that this is only when in the context of judging the position of a pitching ship far from land, and that the model matters more for those fixing the position of stars and planets, and for those who are daring enough to travel between them, as discussed at some length in a later chapter.
