It is scientific insofar as its state of ongoing construction is precisely the same as Relativity was in the early 20th Century - was Relativity a ‘scientific’ theory before it was confirmed by observation? Not strictly, no. It was a description, in mathematical language, of the how-it-is of the universe based on and consistent with the theories which were most definitely scientific. M Theory is the same: it is an incomplete physical model whose observable consequences are as yet unknown.
Now, like I said, even the simple Standard Model has us absolutely straining at our engineering leash to confirm its most important features by observation: bookies offer only 6/1 of the Higgs boson and 500/1 of gravity waves being detected by 2010 even after billions of dollars have been spent thereon. What if the most important aspects of the explanation for how our universe has 3 dimensions of space and one of time, after decades or centuries of humanity’s most fiendishly cunning attempts to rig up the necessary apparatus, are simply unconfirmed by observation? “Ha ha! Look!” would cry the critics, especially those of a theistic persuasion, “They’re as credulous a cult as Xenu-believing Scientologists!” Even some evidence supporting that explanation would probably be like showing a single archaeopteryx tail bone to a Young Earth Creationist: “What? You’re basing a supposedly scientific theory just on that? That could mean anything!”
At this point, yes, all we would have would be our opinions. We would have to look around us and plump for either that explanation or another one, based solely on which neuropsychological configuration induced by each one made us happiest. The one I considered closest to, most consistent with, those strictly scientific theories, would be my choice. Personally, I rejoice that I live at such in exciting period - how dull to live when it’s all been “worked out” (and how depressing to find that the favoured explanation could not be confirmed after all)!
If a solely physical universe existed over all time, there is no law that an explanation for its how-it-is must be confirmable by observation (nor even understanable) by 3 dimensional, temporal configurations of matter having senses and memory existing somewhere within it. Indeed, it is a constant source of wonder and joy to me that we’ve got as far as we have.
Well, OK, although I’d phrase is that string theory is a subset of M theory rather than the other way around. It holds that the fourth through eleventh (or more, sine 11 is a ather arbitrary number in physics: one of my lecturers opined that the answer is always 0, 1 or infinity!) spatial dimensions are “rolled up too small to see” in this region of the universe, just as our third dimension might be in the two-dimension region. It may be that this has observable consequences down at those tiny near-Planck scales, maybe not. Like I said, it’s like passionately watching a footy match knowing that you might lose.
And I try to answer your respectful queries with the good grace they deserve. Time is contingent on change. How can something infinitely small change - it can surely only get bigger? Hence, if t>0 is the only change that can be made, I suggest that no change is possible for t<0, and that one might as well consider the universe as staying exactly the same for times of -infinity to 0: that it is timeless except for the region where time is meaningful.
Is the hypothesis that an infinitely small thing can only get bigger a “scientific” one? No, it is a tautology. As with all logical or mathematical statements, we can never be sure that we are applying them to reality, to the how-it-is, correctly. But Relativity states that time and space are related: this gives us confidence in our approach to the problem.
Just on that last point: you do not consider the study of black holes to be science?
