Micro-Lesson #7: The Ecliptic

Today we need to clarify only one term, but it is an important one: the ecliptic. It is an astronomical term, not astrological, but it's fundamental for understanding many of astrological concepts.

If you look up a definition of the ecliptic on the Internet, you'll find out that it is the apparent path of the Sun on the celestial sphere. However, I find this definition somewhat misleading, especially for non-technical people. When we hear about the path of the Sun, we usually imagine how the Sun rises in the morning in the East, culminates over the head at noon and sets in the West in the evening, but that is not the movement that will help us to understand the ecliptic.

Why the sky is blue? Because the Earth has an atmosphere. If it didn't, we could see both the Sun and the stars at daytime. So let's imagine for the purposes of this lesson that there is no atmosphere, and that today at noon we looked at the sky and noticed that the Sun was in a certain position, in relation to the stars. If you have a spare sky map, you might have marked the position of the Sun on it.

Tomorrow at noon we'll look at the sky and notice that the position of the Sun against the stars has moved a little bit. We'll mark that new position on our map.

If we'll continue to monitor the position of the Sun against the stars like that for the whole year, we'll ultimately draw on the sky map a line, which on the real sky will be a circle. That's the path along which the Sun moves among the stars year after year. The Sun always moves along the same path, and it completes the circle in one year. This path is the ecliptic.

Of course we know that it's the Earth rotating around the Sun, not the Sun rotating around the Earth, and this is why astronomers say that the ecliptic is the apparent path of the Sun. It appears to us, observers on the Earth, that the Sun moves around us.

All the other planets, as well as the Moon, move along the ecliptic but do not exactly follow it. If we mark in the sky the paths of all the planets over many years (as those paths somewhat change year after year), we'll get a road with the ecliptic as its center line. This road is the zodiacal belt, and here we are approaching the definition of the zodiac; however, this will be a topic of a later lesson.

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