Re^2: Most infamous "Last words":

[swampyankee]

Vaguely related are:

Heavier-than-air flying machines are impossible.
— Lord Kelvin, President, Royal Society, 1895.

Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible.
— Simon Newcomb, 1902.

..and this rather disdainful one:

The Americans cannot build aeroplanes. They are very good at refrigerators and razor blades.
— Hermann Goering, German Air Force Minister to Hitler, 1940.

[eric256]

Makes you wonder what current assumptions will be proved wrong by our children

You can't go faster than the speed of light" -- Silly Grandpa

[chacham]

You can't go faster than the speed of light" -- Silly Grandpa

Admittedly, Grandpa's statements do carry too much weight. But, are they such empty formulations that you see to constantly make light of 'em?