P:

Parallax: the apparent shifting of a closer celestial body (a planet or nearby star) against the background of far more distant stars caused by changing one’s point of view. If the two points of view are on opposite sides of the Earth, it is called a "geocentric" or "diurnal" parallax; if on opposite sides of the Earth’s orbit, it is called "heliocentric" or "annual" parallax. Since the distance between those points is precisely known (the diameter of the Earth or its orbit around the Sun), and the angle of shift can be measured, the distance to the closer body can be determined by trigonometry. Parallax is 1/2 of the angle of the aforementioned apparent shift.

In 1672 Giovanni Cassini used a parallax base line from Paris to Cayenne, French Guiana to measure the distance to Mars, and in so doing measured the Earth-Sun distance (1 AU) for the first time. It wasn’t until 1835, however, that the first accurate measurement of a star’s parallax was obtained by Friedrich Bessel for the star 61 Cygni. With a parallax of 0.32 arc-seconds (1/7200th of a degree), its parallax was more than 100 times below the threshold of Tycho Brahe’s ability to measure the position of stars.

Parallel: the aspect between two planets that are the same angular distance north or south of the celestial equator ( the Earth’s equator projected onto the celestial sphere) and are on the same side of it; orb 1°. Two planets with the same "declination" are said to be in parallel; see "declination" and "contraparallel." This aspect is said to act like the conjunction when two planets have the same declination and are on the same side of the celestial equator (in parallel), and like the opposition when two planets have the same declination and are on opposite sides of the celestial equator (in contraparallel).

Parsec: 3.26 light years = 19.2 trillion miles. A parsec is defined as the distance to a body with a heliocentric parallax of one second, hence "par - sec" = "parallactic second." If a body appears to shift one second of arc against background stars when viewed from opposite points in the Earth’s orbit (182 days apart), its distance from the Earth is one parsec. The nearest star other than the Sun, Alpha Centauri C (Proxima Centauri) is 1.3 parsecs or 4.22 light years distant.

Part of Fortune (Pars Fortuna): if the Sun were moved onto the Ascendant and the angle between the Sun and the Moon were left unchanged, the Moon’s new position is the Part of Fortune. It denotes success in worldly affairs.

Perigee: the point in its orbit where an object is closest to the Earth (opposite of apogee).

Perihelion: the point in its orbit where an object is closest to the Sun (opposite of aphelion); the term perigee is used for objects orbiting the Earth; "periapsis" is used for the closest point in orbit around other bodies.

Personal Planets: the Sun, Moon, Mercury, Venus and Mars. These planets change positions fast enough to distinguish birth charts close in time from one another. They are also personal in that they relate to individual rather than to collective or social energy, as do the outer planets.

Placidian: of or like Placidus, the most popular house system in the English-speaking world; probably due to being in the widely circulated 1820 "Raphael’s Almanac and Prophetic Messenger."

Plane: an imaginary, infinite flat surface, like the Meridian or horizon planes.

Plasma: atoms as a gas that have lost some or all of their electrons, either by having been heated or electrically excited. All luminous stars are composed of plasma, similar to the element fire in astrology. The four known states of matter (solid, liquid, gas, plasma) differ only in the degree to which their atoms vibrate. Click here for more on plasma.

Precess (see page 91): A spinning body to which an outside force is applied will tend to rotate in a direction perpendicular to both the outside force and to its spin axis. This resultant rotation is called precession, a movement seen both in spinning tops and in planets.

Precession of Equinoxes (see page 92): Since the Earth is not a perfect sphere (see "oblateness"), the Sun and Moon pull on it unevenly. This non-uniform pull or force causes the Earth’s spin axis to wobble or "precess" in space, the way a top’s axis pulled on by gravity circles the vertical as it slows down. Thus the Earth’s equator and its line of intersection with the ecliptic precess as well. Since this line of intersection is the line of the equinoxes, we get the "precession of the equinoxes." This wobble takes 25,788 years to complete one cycle, or 2150 (25,788÷12) years/sign. A "great age" takes its name from the group of stars (constellation) through which the vernal equinox is currently precessing. Thus the Age of Pisces lasted from about the birth of Christ to the mid-20th century, and the Age of Aquarius will last from the mid-20th century until about 4100.

Prime Vertical: the "vertical circle" passing through the center of the Earth and perpendicular to the horizon (the definition of a vertical circle) that also passes through the east and west points on the horizon. The Prime Vertical is also perpendicular to the Meridian: the vertical circle passing through the north and south points on the horizon. The horizon and Meridian planes quarter the local sky, and form the 12 houses when trisected by planes perpendicular to the Prime Vertical and passing through the horizon’s north - south line (see diagram on page 151).

Progressed: planetary positions (or a whole chart) computed on the principle that one rotation of the Earth on it’s axis (one day) symbolizes one revolution of the Earth around the Sun (one year); said to signify inner development; distinct from transits said to represent exterior events.

Ptolemy, Claudius: (87 to 150 AD), a Greek living in Alexandria, Egypt, codified the Greek geocentric view of the universe in his 12-volume The Almagest (The Greatest). Aristotle and Ptolemy’s perfect geocentric universe became the model for astronomers, astrologers, and, albeit pagan, for the Christian church for 2000 years.

Putti (singular, Putto): angelic creatures used by artists to allude to or to represent love, usually depicted as adorable chubby children or babies with tiny wings suggesting their celestial origin.

Pythagoras (c.569 - c.475 BC): (c.569 - c.475 BC): Nothing of Pythagoras’ writings has survived. His half religious, half scientific society followed a code of secrecy that has left him a mysterious figure. Early biographers attributed divine powers to Pythagoras and presented him as a god-like figure. Nevertheless, we know his primary teachings were that: reality, at its deepest level, is mathematical in nature; philosophy can be used for spiritual purification; the soul can rise to union with the divine; and that certain symbols have a mystical significance.