I have just finished reading Brian Greene's new book, The Fabric of the Cosmos. As with his earlier book, The Elegant Universe, he does a damn good job explaining the almost unexplainable -- string theory, braneworlds, multiple universes, and all that. None of this stuff has an empirical basis, and is not likely to for the foreseeable future. So does it qualify as science?
Well, yes, barely. Because in principle at least experiments are possible. We should value the wild speculations of the theoretical cosmologists precisely because they are pushing the limits of what is imaginable.
We live in an imagined world. Some parts of that imagined world are so tightly bound to sense perceptions that we call them "real." The chair I'm sitting in is real. Atoms are real. The common ancestry of humans and raccoons is real. Strings and branes and multiple universes are not yet real, but they spring from the same storytelling tradition. Democritus and Lucretius told stories of atoms long before atoms were real.
It is ever for us as it was for the singer in a famous poem by Wallace Stevens: "Even if what she sang was what she heard...there never was a world for her/ Except the one she sang, and singing made."