Look forward to reading book. . .but 'till then'; does Lisa describe just what a visitor to the 5th dimension might experience. . .or is it a 'no visitors allowed' plane. . .
Well I guess it would qualify as a 'no visitors allowed' dimension.
The whole thrust of this multi-dimensional push in particle physics is to reconcile the weak gravitational force with the other various forces. This has lead to the current rage - string theory. This theory involves multiple dimensions all but three of which are not visible. The reason they aren't is not well understood and there is no final agreement on how many of them there are. The lowest number is 5. 10 and 11 are in play and 26 is as well. The preferred explanation for why these dimensions are not visible is that they are "curled up" into a loop. Randall discusses all of this in the book. I would buy it and read it. Very interesting stuff.