Okay so I see a few of my favourite questions being kicked around.
1) What is sacred geometry?
And
Why is it sacred?
Ive heard so many ridiculous answers to this
So let me offer mnsho ...
1) My definition is that Sacred Geometry is the study of the fundamental forms of existence to reveal secrets of the physical and spiritual worlds. Its a key to good science, a secret of great art, and a light on the mystical path.
2) Its called sacred because in studying the fundamental forms we are examining the source and nature of existence, and that is by definition 'sacred' if anything is.
If a pattern is not either one of the primary patterns of existence, or one that gives us insights about those primary patterns, then I dont personally think it should be classed as sacred geometry.
Therefore I include the flower of life because it is a study in symmetry and circle packing, and sphere packing is an important concept to explore. I also include metatrons cube because despite not showing an exact projection of the dodeca or icosa it is probably the simplest way to show approximations of the 3d regular convex forms in 2D, and therefore teaches us something important about the symmetry of space again.
However - I am reluctant to include the 'tree of life' design as although it is an interesting study of vertical symmetry and polarity, it is mostly a cultural and religious glyph influenced by the other two forms but not showing any geometric principles that are as essential as theirs. Note that the current form of the tree of life glyph is not very old and that it evolved through many other diagrams people drew to illustrate references in scripture.
I dont know if anyone has mentioned the tradition that sacred geometry is the language of light the angels (non embodied intelligences) speak? One implication I draw from this is that it is the geometry of electromagnetic fields that is primary. The geometric forms are important because they are an evolution from subtler energetic forms - and those energetic forms are the original language of the universe.
For more I recommend
www.SacredGeometryWeb.com