Astro School: Lesson 3. The Zodiac
- The Ecliptic and the Zodiac
- The Signs of the Zodiac
- Tropical and Sidereal Zodiac
- The Symbolic Descriptions of the Signs of the Zodiac
- Studying the Signs
The Ecliptic and the Zodiac
Before we learn anything about the Zodiac, we need to find out what is the ecliptic.
The definition is: the ecliptic is the imaginary path of the Sun across the sky. However, it can be a bit misleading.
We all know that in the morning the Sun rises in the East, and that in the evening it sets in the West. This however is *not* the movement that defines the ecliptic.
To understand what is the ecliptic, we need to imagine that the Earth doesn't have its precious atmosphere that makes the sky blue. As a result, in the middle of a day we would be able to see the Sun against the background of stars.
Say, we decided to track how the Sun moves day by day against the background of stars. We would then notice that its positions changes slowly, just a little bit every day, and it takes the whole year for the Sun to complete the circle around the sky. If we connect all the points on the starry sky through which the sun has passed throughout the year, we'll have the ecliptic.
From the ecliptic to the Zodiac
By definition, the Sun always moves along the ecliptic. The Moon's and the planets' paths against the stars do not coincide with the ecliptic but at the same time they don't go too far from it. This is why the ecliptic is convenient for mesuring the movement of the planets and defining where in the sky they are situated at any specific moment.
There is a zero point on the ecliptic from where all the measurements start, the Point of Vernal Equinox. You don't need to know anything about this point except that it exists, but if you are curious, it is one of the two points where the ecliptic crosses the celestial equator. Pick any good book on astronomy to read more about this.
Astronomers use ecliptical longitude as one of the measurements that allow to precisely define where a planet is located in the sky. As the ecliptic is a circle, ecliptical longitude expressed in degrees and minutes of arc can be in the range from 0° 00' to 359° 59'
Now, imagine that the ecliptic is the center line of the road along which the planets travel. That road is the zodiacal belt, and the location of planets on it is typically expressed in astrology in the Signs of the Zodiac.