This fascinating shape repeats itself in nature from the double helix of the DNA molecule, to the shape of a shell, to a fern, to a galaxy a hurricane and the cream in your coffee.
One form of the spiral arises out of the famous Fibonacci sequence. It is the most sacred of geometry. It is used symbolically in every culture on Earth from the earliest neolithic to today. Its shape, a center starting place then repeating orbits gaining in diameter at a constant rate is generally seen as relating to coming into being, birth, time, growth, life, evolution, cosmic force and emergence.
In modern times it has come to be associated with Pantheism. Think of a spiral as a circle that moves forward and so does not terminate. This is the Dharma. Every orbit is a moment of existence yet each of these moments, rather than being distinct are actually continuous connected in an unbroken spiral to the moment before it and the moment after. In this way time can be seen as an infinite spiral of interconnected moments. Thus, everything that was, is, and ever will be are connected in the spiral of existence.