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 (1941-2002) American paleontologist, geologist, biologist

“Evolution as Fact and Theory” in Speak Out Against the New Right [ed. Herbert Vetter] (1982)

Full text.