Werner Heisenberg

"The present situation in physics is not satisfactory."

"Without speculation there is no good and original observation."

"The existence of electrons and photons is not a philosophical opinion; it is a physical fact."

"Nature requires of the physicist only that he observe, measure and calculate, not that he understand."

"Prudence is the quality of thinking before acting."

"The object of atomic physics is the understanding of the laws of matter, not the production of new materials or useful applications."

"The laws of quantum mechanics are the same for all observers."

"Clarity about the aim and about the means is the first condition of any real success."

"The greatest danger is when those in power believe they don't need to listen."

"Art teaches us that man is not a mechanical automaton."

"The methods of natural science cannot answer the questions of human values and human meaning."

"Success is not final, failure is not fatal: it is the courage to continue that counts."

"A student of mine once asked me: 'Professor, how do you come up with all these good ideas?' I replied, 'I don't think I do. I think God does.'"

"The danger of our time is that we do not understand what is happening to us."

"The laws of nature cannot be broken."

"We must always remember that in physics we are not trying to understand nature for its own sake."

"The physicist may sometimes hope that the present unsatisfactory situation in physics will change."

"I am satisfied that the real satisfying creative experience for the scientist is the result of a process of hard work."

"The most important thing is the willingness to think new thoughts and to do new things."

"We cannot avoid the conclusion that the behavior of the observer has influenced the observed."

"Every time we make a measurement, we introduce an uncertainty."

"The world is not only queerer than we suppose, but queerer than we can suppose."

"Recollection of the past is only possible because in the brain it is written like an engraving."

"The real problem is that in order to describe nature we have to use mathematics."

"Knowledge is power only if we know how to use it responsibly."

"Creativity is the residue of time wasted."

"The interpretation of quantum mechanics is still disputed."

"What we observe is not nature in itself, but our interaction with nature."

"The responsibility of a scientist is not just to society, but to future generations."

"The most decisive steps in human progress usually consist of revelations which at first appear to be destructive of old ideas."