Physicists at TU Dresden have discovered spontaneous static magnetic fields with broken time-reversal symmetry in a class of iron-based superconductors. The past and the future of human life are not symmetric and therefore not reversible. In physics, this is different. The fundamental forces of nature in elementary particles, atoms and molecules are symmetric with respect to their development in time: Forwards or backwards makes no difference, scientists call this a time-reversal symmetry. However, for some years, physicists have been discovering new superconductors which brake time-reversal symmetry. To explain these observations, the basic mechanism of superconductivity, which has been known for...