Planetary alignments are really about vantage point, and in science the term planet alignment can be used in two different ways. From our vantage point on the Earth, the visible planets appear to follow an imaginary line in the sky, known as the ecliptic. This flat circular plane is a reference point describing the apparent path that the sun takes as it travels through our sky in the course of a year.
In actuality, we are the ones moving as the Earth revolves around the sun. Because the other visible planets have similar orbital planes to Earth, they appear to be following the same line when they appear in our sky. As they revolve, sometimes two or more of the visible planets (and or the moon) cluster together or align in a small viewing area of the sky - a fairly common occurrence.
The other type of planetary alignment refers to all the planets forming a straight line outward, if viewed from the sun. Because all planets are tilted on their axis a perfect planetary alignment is impossible. However, considering the fact that the solar system is several billion years old, getting all the planets on the same side of the sun and in the same quadrant of space can and does occur.
In ancient cultures, the study of celestial objects in the sky was used as a guide for life. Knowledge of Mercury, Venus, Mars, Jupiter and Saturn were already known, since these planets are visible to the naked eye. Though scientific understanding of the universe was crude by our standards, ancient observers of the sky accurately calculated planetary motions, created calendars and set up early observatories.
To these early sky gazers however, religious beliefs played a major role in how they viewed the sky and often, ancient astronomers were priests. To them the bright planets wandering around our sky seemed god like in nature. Our ancient ancestors invented astrology and named the planets after their gods. The movement of the planets was used to foretell good and bad events and a planetary alignment was given significant attention. The interpretation of these occurrences could trigger a wedding, a political coup or an assassination of a ruler.
As scientific understanding expanded with the growth of modern astronomy, predictions of bad omens from planetary alignments was given less credence. Ironically, as technology and scientific knowledge continued to expand in the later part of the 20th century the fear and mysticism surrounding the next planet alignment began to gain more attention and believers.
Continue reading on the second page to find out about recent planetary alignments and the one that many say will occur on December 21, 2012