The nature of existence is movement.
Look at “atom smashers” for example. Huh? No, really. In these contraptions, scientists send beams of particles at each other at speeds close to that of light. When the beams collide, it’s time to see what comes out of that. Well, in this process, particles are actually smashed into existence, so to speak. And what these particles do, during their sometimes extremely brief manifestation, is whirl and twirl, as in the cloud chamber picture at right. It’s the dance of existence.
As above, so below. As with the small, so with the large (a bad paraphrase and maybe not perfectly accurate at the quantum level, but cut me some slack here). The heavens are in constant movement, like a large clockwork; that is, like when clockwork had gears. The Earth itself is engaged in several kinds of movement – rotation, revolution, and precession to name three. Precession is the one where the Earth’s axis moves like a child’s top, tracing a slow 26,000 year circle in the heavens. One noticeable consequence of this is that the pole stars change over time. Polaris is the north star now, but it won’t be in a few thousand years; nor was it a few thousand years ago. Another thing that happens is that, from the viewpoint of the Earth, the Sun slowly moves “backwards” through the constellations of the zodiac at the rate of one degree approximately every 72 years.
This also means, of course, that the position of the Sun on the first day of Spring (the equinox, March 
21) also precesses backwards. Here is where Tropical and Sidereal astrology diverge. In Tropical astrology, which is the typical system used in the West, the first day of Spring is the first day of Aries. Period. Every year. Unchanging. But everything is in motion, remember? In reality, on the first day of Spring, the Sun is now still in the sign of Pisces (the fish). That is, if you were to look at the Sun (which you wouldn’t do without adequate eye protection), and could block its brightness, you would see the stars of the constellation Pisces surrounding it. I’ll save you the trouble, and the wait, by giving you a picture (at left), which I constructed using the apps SkyView and Skitch. Ain’t technology wonderful?
In Sidereal astrology, like Asterian or Jyotish, precession is taken into account. So, someone born on March 21 is not an Aries, but a Pisces (and in a few hundred years, someone born on March 21 will be an Aquarius!). In fact, Aries doesn’t start in these systems until the Sun actually enters that constellation, on April 13 this year. What it boils down to is that most people who have thought themselves to be a Taurus are actually an Aries (e.g., me). Same for the other signs. For instance, most who thought they were born in Virgo were born when the Sun was actually in Leo. Furthermore, an approach like Asterian has a system of 27 signs (each one of length 13 degrees, 20 minutes of arc) that overlays the 12 usual solar signs. This fine tunes the system even more, such that there are three types of Aries, etc. Some of the 27 signs cross the boundary between two solar signs. In those cases, there are two types of some of the 27 signs. It’s not quite so confusing as it sounds at first. 
It actually makes more sense than a Tropical approach, since it reflects the reality of the heavens.
I’ve become a convert. After examining the Sidereal description of my personality, it became obvious which approach “nails” it better. I even wrote about it here, and have co-authored a book, entitled 27 Stars: Discovering Your True Self With Asterian Astrology. Without a doubt, I’m siding with sidereal. Examine this approach, and see if it doesn’t make lots of sense to you, too.
