Research Study

Tropical vs. Sidereal Descriptions

Introduction

In this vast universe of ours, there is plenty of room for different approaches to the same problem. The issue in this case is which of the two zodiacal systems describes people more accurately?

The zodiac is defined by Wikipedia as the "imaginary belt in the heavens extending approximately 8 degrees on either side of the Sun's apparent path (the ecliptic), that includes the apparent paths of the Moon and the planets." Along this path lie the signs of which we are familiar. Usually, when a person describes herself as an Aries, she is referring to the sign the Sun was traveling through at the moment of her birth. Or was it really Pisces? At this point we have at least two camps of thought on how to define the measurement of this planetary path.

We all know that the earth, Moon, and planets revolve around the Sun. Yet, from where we stand on earth, it appears that the Sun, Moon, and planets move around us. Hence, you'll see references to the "apparent" path of the celestial bodies because they "appear" to circumscribe a path around us. This 360 degree path is divided into 12 sections of 30 degrees each. Each 30 degree section is governed by one of the constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

In addition to the ecliptic path of the zodiac, let's imagine another plane defined by the earth's equator projected onto that ecliptic. The earth tilts on its axis 23.5 degrees relative to the zodiac. At the point where the ecliptic intersects the equatorial plane two events occur. One is called the vernal equinox, the other is the autumnal equinox. On the vernal equinox the Sun begins its ascent into the northern hemisphere. This point of intersection occurs every year on March 21st and is associated with Aries. It marks the beginning of Spring. This point begins the zodiac used by many astrologers in the western hemisphere and is called the tropical or seasonal zodiac. Yet, at that moment, the Sun actually is in Pisces and doesn't really enter Aries until April 13th. The sidereal approach measures the sky according to the actual positions of the planets as seen against the zodiac. Sidereal means star, so in this system, the unchanging backdrop of the stars define the path of the planets. This is the zodiac used by many of the eastern practitioners including the Vedic astrologers.

So why do we have two systems, one based on seasons and the other based on stars? The answer is in the precession of the equinoxes. Over two thousand years ago, the tropical and the sidereal zodiacs were in alignment. But as the years rolled by, they separated so that today we have a nearly 24 degree difference which is called ayanamsa. The separation is caused by the wobbling of the earth on its axis (precession of the equinoxes) which is accounted for by the sidereal zodiac, but not by the tropical zodiac. Many successful interpretations have been based on the sidereal zodiac. The same can be said of the tropical zodiac. Hence, the confusion.


The Study Hypothesis and Methodology

My study was an attempt to determine which zodiac better described people. Would the same person identify himself more as a sun in Aries than as a sun in Pisces? Each has a distinct way of expressing individuality in the world. Likewise, distinct descriptions can be made for the placements of all the other planets. Emotional significations are different if the moon is in Gemini rather than Taurus. The assertive energy of Mars manifests differently in Aquarius than it does in Capricorn. The null hypothesis was taken, meaning that it was assumed that no significant differences existed between the two systems.

Fortunately, today's astrological software can calculate charts in either zodiac. For this study, I used Halloran's AstrolDeluxe ReportWriter, version 6.3. I also gave short, interpretative descriptions for each planetary placement from the Spirit Success companion report software written by astrologer Carolyne Lacy.

I asked twenty-five friends and relatives to participate in the study and received twenty-three usable surveys. Everyone received a survey of 30 to 40 or so descriptions derived from the Spirit Success interpretation based on their birth data. The nine planets, the ascendant, and the north nodes in the signs were given. Descriptions came from both tropical and the sidereal calculations when there were differences because it is possible to have any of the planets reside in the same sign for both systems if those planets are between 23-30 degrees of the tropical system. In these cases, there was no point in having the respondents rate identical statements, hence an N of less than 23.

Descriptions were interspersed with one another with no identifiable clue as to what zodiac or even what planetary placement they represented. Respondents were asked to rate each description on a five point scale with 5 equal to 'exactly like me" to 1 equal to "not at all like me."

A t-test was used to determine level of statistical significance for each point calculated. Results are shown in Table 1.


Results

 

N

Sum

Sum

Average

Average

Diff

Std Dev

Std Dev

T-Test

 

 

Tropical

Sidereal

Tropical

Sidereal

 

Tropical

Sidereal

 

ASC

18

44

62

2.444

3.444

-1.000

1.247

1.247

0.015*

Sun

18

51

45

2.833

2.500

0.333

1.581

1.200

0.369

Moon

21

51

48

2.429

2.286

0.143

1.502

1.231

0.505

Mercury

16

52

37

3.250

2.313

0.938

1.528

1.302

0.043*

Venus

18

40

38

2.222

2.111

0.111

1.003

1.231

0.726

Mars

20

51

55

2.550

2.750

-0.200

1.395

1.372

0.592

Jupiter

19

60

68

3.158

3.579

-0.421

1.500

1.216

0.249

Saturn

19

54

46

2.842

2.421

0.421

1.385

1.216

0.288

Uranus

19

48

50

2.526

2.632

-0.105

1.124

1.012

0.716

Neptune

20

53

48

2.650

2.400

0.250

1.422

1.273

0.522

Pluto

18

38

38

2.111

2.111

0.000

1.269

1.183

1.000

MNN

18

43

49

2.389

2.722

-0.333

0.970

1.320

0.231

Total

23

585

582

25.435

25.304

0.130

7.555

7.836

0.892

In social science search, a probability of less than five percent is considered significant. There are two areas of significance. The ascendant description was rated significantly higher for the sidereal than for the tropical. The Mercury description was rated significantly higher for the tropical than for the sidereal.

The Ascendant, or rising sign, is important in both systems because it describes the personality, appearance, and temperament. It essentially shows how a person appears to others.

Mercury is the planet that governs communication and transportation. It shows how a person interacts with others.

Obviously, these are two very important parts of a chart, but no explanation can be given for their significance or for the non-significance of the other points in the chart. As many know, when in consultation with an astrologer, the chart is read as a synthesis of many factors not included in this research such as aspects among planets, planets in houses, and modalities. Aspects are not different between systems, but house placement and modalities change. These were measured in this study and results will be given in a future article. The fact remains that an astrological reading is more than a set of sign placement descriptions. Computerized reports can never replace the wisdom of a truly knowledgeable practitioner. In any field.

This is a pilot study. It would be very interesting to mount this study on a larger scale with more subjects. The ultimate study, though, would have subjects rate readings given by astrologers (not computers) from both tropical and sidereal approaches.

The results confirm the popularity of both zodiac systems and why they thrive today among astrologers and their clients. Both tropical and sidereal systems seem to do their job equally well. The universe has uncannily found a way to accomodate two seemingly disparate approaches to describing the human condition.