Prediction Is Very Difficult Especially About

This quip is attributed to Niels Bohr and is deeply embedded in Danish scientific culture, though no specific written source has been pinpointed. Variants of the saying have circulated in Scandinavian academic circles and appear in books of Danish wit. The humor lies in its self-defeating logic — a true statement about the limits of prediction — which suits Bohr's fondness for paradox and his work in quantum mechanics, where the future behavior of particles is inherently probabilistic.