I have maintained here several times , amid howls of objection from a few, that spacetime IS something more than a mathematical construct or that at least we should maintain an open mind about that possibility. I have been thinking WHY I have that view and a significant reason is the presence of vacuum energy and virtual particles. Seems like those are theoretical entities which manifest only via spacetime. Is that true or can other entities produce vacuum energy via quantum fluctuations and virtual particles? And do we even have solid experimental evidence for vacuum energy and virtual particles? Wikipedia sez on vacuum energy: In Lamb shift, wikipedia says, for example: http://en.wikipedia.org/wiki/Lamb_shift I never heard of van der Waals bonds before and a quick scan in Wiki did not cause me to jump out of my chair in excitement...but since DARPA is experimenting something must be going on.... Any consensus on those "observations"? as evidence? I'm somehwat familiar only with the Casimir effect and don't really think it shows observational "proof" of vacuum energy, but I do take it to be a signpost in that direction. Ditto for Lambshift. Maybe we should think of spacetime as a feature derived from vacuum energy, quantum jitters?