In the Cosmology forum a reference by Marcus references an article in Scientific American I think might be of interest to Quantum Physics readers: (What are the (quantum) building blocks of space and time?) http://www.signallake.com/innovation/SelfOrganizingQuantumJul08.pdf [Broken] (by Ambjorn, Jurkiewicz and Loll) Here's a series of excerpts which provides an overview of the paper, a quantum gravity model: (Italic scripts are my additions for clarity from other portions of the text ) All of which sounds like some really interesting work. Now my simple minded questions: Inputs: simple triangles, gravity, quantum theory, causality, time, and a cosmological constant (vacuum energy); Output: spacetime... (1) Seems like a possible model for today, with expanding space....but how did it start???? Were all those input quantities ALWAYS present?? Seems like an awful lot of "stuff" to have sponaneously emerged all at once!!!!! Seems too complicated.. (2) If you put in causal structure, do you automatically get out some kind of Lorentzian manifold of which de Sitter space is one? I think de Sitter space is slightly curved even in the absence of matter or energy. Is this a significant result??