Astro*Dictionary by Michael Erlewine

2 articles for "Coordinate"

Coordinate [DeVore]

n. Any of two or more magnitudes that determine position. Latitude and Longitude are coordinates of a point on the Earth's surface. v. Celestial Sphere.

♦ Celestial Sphere
Coordinate System [Astro*Index]

Any way of locating points in a space by referring them to certain lines, circles, or points. One way is to find their distances from these reference as measured along an an ordinate or line drawn in a specified way to another line (such as at right angles). Another way it to join the point in question to a fixed reference point and specify the angle that this line makes with a fixed reference line as one of the coordinates. In order to locate a point in space, it is necessary to have as many coordinates as their are dimensions in the space.

The most important system of coordinates for general mathematical purposes is Cartesian coordinates, which locates points in terms of their distances from certain coordinate axes in much the same way that a city map fixes places by the intersection of numbered streets and avenues.

Spherical coordinates use great circles on the surface of a sphere as reference lines just as we use longitude and latitude to fix places on a globe. The longitude and latitude and difference from a fixed center serve to locate a point in three dimensional space. Spherical coordinates are especially useful in astronomy and astrology.

Various particular systems of spherical coordinates have been developed for special terrestrial, astronomical or astrological purposes through the selection of convenient centers and reference circles. Knowing how to locate points in a given system, it is then possible to characterize any given line or figure, by making use of a geometrical property that all the points of the line or figure have in common, and expressing this property in terms of the coordinates used. This give rise to an equation corresponding to line or figure. For example, all the points of a circle are equidistant from its center. If we take an arbitrary point on the circle (represented by the indeterminate coordinates X & Y) The operation of converting from one system of coordinates to another is called a transformation of coordinates. If we carry out a transformation of coordinates from one coordinate system to another of the same type--say, if we use different axes and a different origin in Cartesian coordinates--then the equation for any line changes into a new one that is generally of the same algebraic form as the first, differing from it mainly in value of the coefficients. However, if we transform from one system into another of a totally different type, then the resulting equation will have an entirely different form.

So far we have only been concerned with directly locating points in the real space of our existence; for example, the place of an event such as a birth or the position of a planet at a certain time. However, coordinate systems may also be used to represent various phenomena of our world in a more indirect and abstract way. If we make one of the axis in a Cartesian coordinate system stand for time, and the other for distance, then we can represent a motion (understood as a certain distance traversed in a given time) by a line. A line in such a coordinate system does not look like a motion the way that a city map is a model of the city, but stands for it or symbolizes it as long as we keep in mind the conventions that define the coordinate system. Even more abstract are "state spaces" in which the various coordinates may be temperature, pressure, etc. A point in such a system represents the overall state that a physical system is in at a certain moment. Astrologers use spherical coordinates. Some believe that astrological charts calculated using different centers or axes at different inclinations bring out or emphasize different aspects of the same entity or event. Thus, in the opinion of astrologer Michael Erlewine, horizon coordinates and local space astrology are advantageous in the study of what is particular and accidental to us as individuals. Ecliptic coordinates (zodiacal coordinates) and geocentric astrology best bring out what different men have in common as to their psychological types, while equatorial coordinates in geocentric astrology (which differ from ecliptical coordinates only in the inclination of their axes) may pertain to the political or mundane affairs upon the earth, things affecting men generally. Heliocentric Coordinates relate even more generally to life-paths and spirituality. And it is even possible to consider coordinate systems of perhaps broader significance such as the galactic and supergalactic.