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shminux comments on [Poll] Less Wrong and Mainstream Philosophy: How Different are We? - Less Wrong
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Why then does SEP not mention it in the discussion of this A and B stuff? Certainly detracts from its credibility.
Because it is not relevant. B-theory time and A-theory time are not related like an affine space is related to a vector space. You can't get from B-theory time to A-theory time by picking an origin and calling it "the present". The whole point of the A-theory is that the present is not a static point in time. It moves. The particular mathematical representation you suggest doesn't capture this.
Right, I was pondering that, too:
Indeed the transformation does not capture this apparently moving origin. What does "moving" mean in this context? How would you describe it mathematically? In the block universe model, this is ought to be pretty easy by introducing a shifting origin, but it is probably harder in the growing block universe model. I need to think about it some more, feel free to point me to any mathematical references if you know of any. Though I do not think I will continue in this thread, due to the distracting karma burn it seems to extract, reminding me that, on average, people don't want me to.
This paper gives a reasonably rigorous mathematical treatment of the growing block model in the Newtonian, relativistic and causal set contexts. Also see this paper for a discussion of whether quantum gravity offers brighter prospects for A-theory than classical relativity. Let me know if you'd like ungated versions of either of these.