Space elevators will be wonderful... if they are feasible. We have yet to identify a material with sufficient tensile strength to construct a space elevator, and may never do so.
[...] it might be assumed that the flying machine which will really fly might be evolved by the combined and continuous efforts of mathematicians and mechanicians in from one million to ten million years--provided, of course, we can meanwhile eliminate such little drawbacks and embarrassments as the existing relation between weight and strength in inorganic materials.
Hence the "if". I certainly hope they will be feasible, but the fact that an alternative may be possible, contingent on the potential creation of currently nonextant materials, is absolutely not a reason to discourage development of supersonic aircraft.
That Asimov quote is actually pretty damned close to reality. Why is that exchange, of all things, sitting beside Neville "Peace for our times" Chamberlain?
