Which German physicist formulated the uncertainty principle in 1927?

Werner Heisenberg formulated the uncertainty principle in 1927. The principle states that certain pairs of quantum properties—most famously a particle’s position and momentum—cannot both be known with unlimited precision at the same time. Improving the precision of one places a fundamental limit on the precision of the other.

Heisenberg developed the idea while working in Copenhagen and published it in his 1927 paper on quantum mechanics. His original discussion focused on the disturbance caused by measurement. The familiar mathematical relation involving statistical standard deviations was formalized later that year by Earle Hesse Kennard and subsequently generalized by other physicists.

A common mix-up is to credit Niels Bohr because Heisenberg worked at Bohr’s institute and Bohr helped refine the interpretation. Max Planck was a major pioneer of quantum theory, while Erwin Schrödinger developed wave mechanics. Heisenberg’s uncertainty principle is one of the defining ideas of modern quantum physics.