In science, "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional assent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.
Stephen Jay Gould
Inanimate objects can be classified scientifically into three major categories; those that don't work, those that break down and those that get lost.
It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.
It will free man from the remaining chains, the chains of gravity which still tie him to this planet.
Wernher von Braun
Leave the atom alone.
E. Y. Harburg