I am also highly sceptical when someone says, "it can never be done,"
I am the proud possessor of a pile of 'Flight' magazines from 1912 to 1918. In one of the articles a professor of medicine from Birmingham University (England) states that it is physically impossible for a human to fly at more than 250 miles an hour as his chest will cave in.
Unless you are dealing with a law of thermodynamics, the future can be anything the human imagination can conceive.
At Freidrischhaven this year there will be a good selection of electric motors and aeroplanes, many more than even five years ago. It is happening now.