Hobbies And Interests
Definition
Planetary alignment refers to the way planets appear to be positioned in the night sky. Astronomers use the term to mean that all the planets appear to extend out from the sun in a straight line. This is, in actuality, impossible, because each planet's orbital tilt is slightly different relative to the Earth's orbital tilt. A more accurate term is "planetary conjunction" as on some occasions, several planets' orbits are close enough to each other that the planets appear to be grouped together when watching them.
Orbital Path
In order to calculate planetary alignment, scientists need to be able to calculate each planet's orbital path around the sun relative to the Earth's relative path. This is because people view the night sky from Earth; what they see each night depends on where they are in Earth's orbital path. How the paths intersect depends on how the Earth is tilted and how the other planets are tilted during this time of year.
Frequency
Planetary alignment involving all the planets is very rare. It happens about once every 200 years. This is because all the planets must be on the same side of the sun at the same time in order to have such an alignment. The last such alignment happened in 2000.
More frequently, groups of three to five planets come together in the night sky. This phenomenon happens once every 40 to 50 years. An alignment of four planets (Mercury, Mars, Venus, Saturn) occurred in April 2002, and astronomers expect the next such alignment in 2040.
Natural Phenomena
Many people are interested in how scientists predict planetary alignment because they believe that natural disasters or strange weather patterns are caused by planetary alignment. However, this does not appear to be the case. There were no more incidents of natural disasters or weather emergencies during the planetary alignment in 2000 than there were at other times.
Computer Software
The mathematical calculations required to predict planetary alignment are complex. Astronomers use a variety of computer software to help them predict planetary alignment. Non-astronomers can also use software to help them understand what to expect to see in the night sky.