23 February 1927
On this day in 1927 Werner Heisenberg’s uncertainty principle is first mentioned in a letter from Heisenberg to physicist Wolfgang Pauli.
Published by Werner Heisenberg in 1927, the uncertainty principle was a key discovery in the early development of quantum theory. It states that it is impossible to measure both the present position and also the momentum or speed of a particle, or of any system small enough to require quantum mechanical treatment.
His work in the field of theoretical physics earned him the Nobel Prize for physics in 1932 ‘for the creation of quantum mechanics.‘