Conjunction of Planets is a fascinating exploration of the science behind the alignment of planets in our solar system. It examines the various factors that can cause planets to align, from gravitational forces to the effects of the sun and moon. It also looks at the history of planetary conjunctions
From Wikipedia
In astronomy, a conjunction occurs when two astronomical objects or spacecraft appear to be close to each other in the sky. This means they have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.