My first thread here. Please bear with my lack of knowledge. I talked to a physics grad student about whether it's fair to describe QM as a theory applied only to microscopic objects. Although the definition of "fair" is ambiguous, at least he told me that, from his understanding, he wouldn't apply QM to macroscopic objects. (Other than that, it seems like if QM doesn't have a GR-like descriptional power, he'll refute to say that QM applies to big things.) But I think the consensus seems to be that it's the interection with environment that counts. Then I remember having heard someone talking about macroscopic QM related to a certain gravitational wave detector experiment. Some quick searches give these results, in chronological order. 1) Zurek's Physics Today decoherence article refers to the paper by Caves et al.and say that we need to apply quantum mechanics to the Weber bar that weighs a ton. 2) http://physics.aps.org/articles/v1/3%20 [Broken] Published July 14, 2008 A part of the abstract 3) http://iopscience.iop.org/1367-2630/11/7/073032/fulltext#SECTIONREF Published 16 July 2009 A part of the abstract Did the approach in 1) successful? What're the difference between 2) and 3)? I'd like to hear from experts here how much has been done and what we can expect, or want to see, in this direction.