"It is apparent to me that the possibilities of the aeroplane, which two or three years ago were thought to hold the solution to the [flying machine] problem, have been exhausted, and that we must turn elsewhere." - Thomas Edison
"There has been a great deal said about a ... rocket shot from one continent to another, carrying an atomic bomb and so directed as to be a precise weapon ... I say, technically, I don't think anyone in the world knows how to do such a thing. and I feel confident it will not be done for a very long period to come. I think we can leave that out of our thinking. I wish the American public would leave that out of their thinking." - Dr. Vannevar Bush
Edited: what I meant by the above is that humanity has a solid track history of mis-estimating the pace of progress in new fields.