arlesterc said:
I was watching a seminar on black holes and one of the participants threw out as an aside that spacetime could travel faster than the speed of light - so within spacetime nothing could travel faster than spacetime but spacetime itself however was not bound by this rule so it could move faster than the speed of light. Is that correct? If so, is there some speed postulated that that even space-time could not move faster than?
People sometimes do try to explain black holes in this manner: for instance we have "The River Model of Black Holes",
http://aapt.scitation.org/doi/10.1119/1.2830526 Probably the main reason why this approach is not very popular is that the concept of "the speed of space-time" is something that is not physically observable according to special relativity. So the theory is described in terms of concepts that don't have any observable physical basis.
This is a rather serious criticism, and I seem to recall some comments by the author that he had difficulty getting his paper published, presumably for this very reason. If you overlook this significant problem with the presentation, though, the idea can be made to work correctly, in spite of the problems with the lack of an underlying physical basis.
Probably my biggest concern with this approach is that if presented to a target audience unfamiliar with special relativity who do not realize that "the speed of space-time" is something that's not physically observable, they will be confused on some important points about what special relativity says. This is relevant because general relativity is built on top of special relativity as a foundation, though many casual science readers attempt (and mostly fail, IMO) to learn something about general relativity without first understanding special relativity :(.
That said, this presentation does avoid some of the issues with the "time stops at the event horizon" approach to black holes, an approach that is also widely misunderstood and frequently leads to misconceptions about black holes and incorrect conclusions.
Another concern I have is how popular this idea is among professionals. This would best be measured by it's impact rating. I strongly suspect that it's impact rating would be rather low, indicating a lack of interest in the approach by professionals, but I don't have any hard data on that - I know that there are databases that try to estimate the "impact factor" of published papers via tracking citations, but I'm not sure where to get the raw data.
