Posted: Sep 29, 2010 9:53 pm
by hackenslash
Oldskeptic wrote:How can someone claim to understand Greene’s writing, or even be well acquainted with it and not know the relationship between string theory and branes?


Spectacularly good question, and a headshot. If I had not been reading from a proxy from which I could not post when I read this vacuous comment, I would have posted much the same in response.

@Hachenslash:
Here is what Maryann is going on about. It begins on page 404 and ends at page 412.

http://books.google.com/books?id=DNd2K6 ... al&f=false

Because of increasing entropy even in cyclical models cycles cannot be eternal. Therefore the “universe” had a beginning, and of course something had to be the “cause” of the beginning. Therefore God made it so.


Well, if you read the Greene on this point, he does concede that entropy seems to provide a barrier to an eternal past, but this actually constitutes an assumption. Firstly, the 2LT is an experimental law, and may only be a feature of the coarse-graining of our four-dimensional Minkowski spacetime, and it isn't clear at all that the 2LT applies in all cases, and especially in the instantiation of said spacetime. In other words, this constitutes a fallacy of composition. Secondly, what is admitted by all advocates of the brane-worlds model is that the mathematics at the 'bounce' is incomplete, and indeed may remain so. It may well be that 'dark energy' or some form of cosmological constant has some part yet to play in all of this. Ultimately, the poster is talking through his arse, and asserting categorically that which is not established. Finally, any citation of entropy in the aforementioned book is subject to my major objection cited earlier, although this is a more trivial concern, and may not actually be applicable in this instance.

I've just pulled the book off the shelf and I will scan the pages in question again to see just what it is he is saying. What is absolutely clear here, though, is that our interloper hasn't actually read the book, or she would have made the connection between M-Theory and the brane-worlds model, since Greene explicitly talks about M-theory and its connection to the work of Turok and Steinhardt.