Sidereal or Tropical? The two Solar Zodiacs.

Figure provided by for study purposes only. Copyright applies.

Most lasting cultures have at some point in their history produced, adopted, or adapted an astrological system. The uses vary from expanding self knowledge to explaining powerful events to predicting future possibilities. What is common about most of them is the inspiration and basis of their origin — and it had little to nothing to do with their eventual use as tools for metaphysical work.

The sources of astrology and the sources of the various calendar systems throughout history are the same. Humans intuited a need for an accurate means of marking time, and the regular motions of the Sun and Moon against the background of fixed stars provided that means. Modern time measurement uses more sophisticated methods such as the decay of radioactive atoms or the vibrational speed of crystals but even these retain the underlying concepts of months (moon cycles) and years (solar cycles). These modern methods require equipment that is expensive to create and maintain and require great skill and care in use. The ancient sages, however, weren’t interested in tracking time to the nanosecond or observing effects such as time dilation, multiple timelines, and measuring the affect of mass and gravity on relative motion.

The calendars of old performed important functions such as marking the seasonal flooding of fertile soil, the migratory patterns over time of animals hunted as food, and marking the gestation periods of mothers-to-be from many species. And just as these events, observed over long spans of time and repetitive cycles of planetary movements, yielded extraordinary improvements on “predicting” the birth of a child, the time to plant, the time to harvest, or the onset of various seasons such as summer monsoons or winter freezes, the keen eye of ancient wisdom masters noted myriad other effects concurrent with particular patterns in the heavens. Learning to read the patterns and relate them to potentials for predictable activities became a profession unto itself, the work of the professional astrologer.

In western civilization, the Greeks perfected their 12-sign version as an improvement on work of the Sumerian, Babylonian and ancient Persian astrological methods. This system, formally called Hellenic Astrology, uses a Tropical Zodiac and is based on the cuspal dates of the four seasons. Beginning some 2000 years ago, Greek astronomers declared that the Spring Equinox, which they measured as the point in the Zodiac where the Sun could be found on the date it crossed the equator from south to north, marked the beginning of the Zodiac at 0 degrees of the constellation Aries. As far as western astrology is concerned, it has remained there ever since.

This tropical zodiac is based on a fixed point in space, what physics would describe as location marked by the intersection of an x, y, and z axis, critical for understanding relationships between objects.

The ancient Rishis of Northern India, close observers of all of nature and life, created a calendar thousands of years earlier. Seeing the concurrences marked by patterns of Sun, Moon, planets, and stars, they developed the system of Vedic Astrology.

The Rishis were excellent astronomers and were among the first to note a slow wobble in the earth’s axis that caused the intersection between the sun and the equator to travel slowly backwards through the zodiac. This discovery meant that the spring equinox would transit all 12 signs approximately every 24,000-25,000 years.

This procession is the basis of the Sidereal Zodiac that forms the most obvious difference between Vedic and Western astrology. On March 21, if one measures the location of the Sun, it will currently be found not at 0 degrees Aries, but at slightly less than 6 degrees of Pisces.

Physicists measure direction of motion by calculating the location of an object over time. Combining this principle with that of fixed points, the rule states we can either know the exact location of an object or the direction of it’s movement, but not both at the same time.

This procession of the equinoxes makes for a significant difference in planet and house locations of Vedic astrological charts compared to Western. There are many other differences I’ll discuss later, but as we celebrate the Equinox season, seeking answers to many challenging questions of modern life, taking a look at how we frame knowledge over time and space is one possibility for gaining wisdom.

The 24 degree difference between the Tropical and Sidereal zodiacs means that for 5 out of 6 people, the Sun sign given in Western charts is actually one ahead of the Sun’s actual location. Does this change who you are? Of course not, but it does perhaps offer an opportunity to look at yourself from another point of view, and in so doing gain greater understanding of your potential.

There are many more fascinating practices the Rishis developed over many centuries before the first Greek city-states formed. For detailed explorations and help understanding Vedic wisdom and your birth chart, a natal astrology reading is the starting point. See my services page on this site for details if you are interested.

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