It's generally a bad idea to say something can't or won't be done, especially in the realm of science and technology.
The following are quotations from the past that haunt their speakers today:
"I think there is a world market for maybe five computers." -- Thomas Watson, chairman of IBM, 1943.
"Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and weigh only 1.5 tons." -- Popular Mechanics, 1949
"I have traveled the length and breadth of this country and talked with the best people, and I can assure you that data processing is a fad that won't last out the year." -- The editor in charge of business books for Prentice Hall, 1957.
"But what...is it good for?" -- Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
"There is no reason anyone would want a computer in their home." -- Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977.
"640K ought to be enough for anybody." -- Attributed to Bill Gates, 1981, but believed to be an urban legend.
"This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." -- Western Union internal memo, 1876.
"The Americans have need of the telephone, but we do not. We have plenty of messenger boys." -- Sir William Preece, chief engineer of the British Post Office, 1876.
"The wireless music box has no imaginable commercial value. Who would pay for a message sent to nobody in particular?" -- David Sarnoff's associates in response to his urgings for investment in the radio in the 1920s.
"While theoretically and technically television may be feasible, commercially and financially it is an impossibility." -- Lee DeForest, inventor.
"The concept is interesting and well-formed, but in order to earn better than a 'C', the idea must be feasible." -- A Yale University management professor in response to Fred Smith's paper proposing reliable overnight delivery service. (Smith went on to found Federal Express Corp.)
"Who the hell wants to hear actors talk?" -- H. M. Warner, Warner Brothers, 1927.
"I'm just glad it'll be Clark Gable who's falling on his face and not Gary Cooper." -- Gary Cooper on his decision not to take the leading role in "Gone With the Wind."
"A cookie store is a bad idea. Besides, the market research reports say America likes crispy cookies, not soft and chewy cookies like you make." -- Response to Debbi Fields' idea of starting Mrs. Fields' Cookies.
"We don't like their sound, and guitar music is on the way out." -- Decca Recording Co. rejecting the Beatles, 1962.
"Radio has no future. Heavier-than-air flying machines are impossible. X-rays will prove to be a hoax." -- William Thomson, Lord Kelvin, British scientist, 1899.
"So we went to Atari and said, 'Hey, we've got this amazing thing, even built with some of your parts, and what do you think about funding us? Or we'll give it to you. We just want to do it. Pay our salary, we'll come work for you.' And they said, 'No.' So then we went to Hewlett-Packard, and they said, 'Hey, we don't need you. You haven't got through college yet.'" -- Apple Computer Inc. founder Steve Jobs on attempts to get Atari and HP interested in his and Steve Wozniak's personal computer.
"If I had thought about it, I wouldn't have done the experiment. The literature was full of examples that said you can't do this." -- Spencer Silver on the work that led to the unique adhesives for 3-M "Post-It" Notepads.
"It will be years -- not in my time -- before a woman will become Prime Minister." -- Margaret Thatcher, 1974.
"I see no good reasons why the views given in this volume should shock the religious sensibilities of anyone." -- Charles Darwin, The Origin Of Species, 1869.
"With over 50 foreign cars already on sale here, the Japanese auto industry isn't likely to carve out a big slice of the U.S. market." -- Business Week, August 2, 1968.
"That Professor Goddard with his 'chair' in Clark College and the countenancing of the Smithsonian Institution does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react--to say that would be absurd. Of course, he only seems to lack the knowledge ladled out daily in high schools." -- 1921 New York Times editorial about Robert Goddard's revolutionary rocket work. The remark was retracted in the July 17, 1969 issue.
"You want to have consistent and uniform muscle development across all of your muscles? It can't be done. It's just a fact of life. You just have to accept inconsistent muscle development as an unalterable condition of weight training." -- Response to Arthur Jones, who solved the "unsolvable" problem by inventing Nautilus.
"Ours has been the first, and doubtless to be the last, to visit this profitless locality." -- Lt. Joseph Ives, after visiting the Grand Canyon in 1861.
"Drill for oil? You mean drill into the ground to try and find oil? You're crazy." -- Workers whom Edwin L. Drake tried to enlist to his project to drill for oil in 1859.
"Stocks have reached what looks like a permanently high plateau." -- Irving Fisher, Professor of Economics, Yale University, 1929.
"There is not the slightest indication that nuclear energy will ever be obtainable. It would mean that the atom would have to be shattered at will." -- Albert Einstein, 1932.
"The bomb will never go off. I speak as an expert in explosives." -- Admiral William Leahy, U.S. Atomic Bomb Project.
"Airplanes are interesting toys but of no military value." -- Marechal Ferdinand Foch, Professor of Strategy, Ecole Superieure de Guerre.
"There will never be a bigger plane built." -- A Boeing engineer, after the first flight of the 247, a twin engine plane that holds ten people.
"Everything that can be invented has been invented." -- Attributed to Charles H. Duell, Commissioner, U.S. Office of Patents, 1899, but known to be an urban legend.
"Louis Pasteur's theory of germs is ridiculous fiction." -- Pierre Pachet, Professor of Physiology at Toulouse, 1872.
"The abdomen, the chest, and the brain will forever be shut from the intrusion of the wise and humane surgeon." -- Sir John Eric Ericksen, British surgeon, appointed Surgeon-Extraordinary to Queen Victoria 1873.