In 1939, Einstein wrote that black holes cannot exist (Einstein, A. 1939, AnMat, 40, 922) and in 1936 said that there can be no gravitational waves (http://www.physicstoday.org/vol-58/iss-9/p43.html ). Appealing to authority is not the way to have a discussion.
As for the nature of spacetime, see the recent contributions;
http://www.arxiv.org/abs/0707.0380
Expanding Space: the Root of all Evil?
Authors: Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis
(Submitted on 3 Jul 2007)
Abstract: While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.
and
http://www.arxiv.org/abs/0707.2106
Coordinate Confusion in Conformal Cosmology
Authors: Geraint F. Lewis, Matthew J. Francis, Luke A. Barnes, J. Berian James
(Submitted on 13 Jul 2007)
Abstract: A straight-forward interpretation of standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies is that objects move apart due to the expansion of space, and that sufficiently distant galaxies must be receding at velocities exceeding the speed of light. Recently, however, it has been suggested that a simple transformation into conformal coordinates can remove superluminal recession velocities, and hence the concept of the expansion of space should be abandoned. This work demonstrates that such conformal transformations do not eliminate superluminal recession velocities for open or flat matter-only FRLW cosmologies, and all possesses superluminal expansion. Hence, the attack on the concept of the expansion of space based on this is poorly founded. This work concludes by emphasizing that the expansion of space is perfectly valid in the general relativistic framework, however, asking the question of whether space really expands is a futile exercise.
and
http://www.arxiv.org/abs/astro-ph/0610590
A direct consequence of the expansion of space?
Authors: Michal Chodorowski (Copernicus Center)
(Submitted on 19 Oct 2006 (v1), last revised 27 Mar 2007 (this version, v3))
Abstract: Consider radar ranging of a distant galaxy in a Friedman-Lemaitre cosmological model. In this model the comoving coordinate of the galaxy is constant, hence the equations of null geodesics for photons traveling to the distant galaxy and back imply the following equation:
\int_{t_e}^{t_r} dt/a(t) = \int_{t_r}^{t_o} dt/a(t).
Here, t_e, t_r and t_o are respectively the times of emission, reflection and observation of the reflected photons, and a(t) is the scale factor. Since the universe is expanding, a(t) is a monotonically increasing function, so the return travel time, t_o - t_r, must be greater than the forward travel time, t_r - t_e. Clearly, space expands, and on their way back, the photons must travel a longer distance! The present paper explains why this argument for the expansion of space is wrong. We argue that, unlike the expansion of the cosmic substratum, the expansion of space is unobservable. We therefore propose to apply to it -- just like to the ether -- Ockham's razor.
