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Superconductivity is a complete loss of electrical resistance. Superconductors are not merely very good metals: it is a fundamentally different electronic state. In normal metals, electrons move individually, and they collide with defects and vibrations in the lattice. In superconductors, electrons are bound together by an attractive force, which allows them to move together in a correlated way and avoid defects. In a very small number of known superconductors, the onset of superconductivity causes spontaneous electrical currents to flow. These currents are very different from those in a normal metal wire: they are built into the ground state of the...

(The University of Queensland) =============================================================== Like watching a movie in reverse, physicists have just demonstrated a new technique for the time-reversal of a wave of optical light. That doesn't mean that they have actually reversed the flow of time; rather, they have found a way to induce an optical wave to retrace a forward path in reverse, returning to its point of origin. It's the first time that time reversal of optical waves has been achieved with full control over all of the degrees of freedom of light simultaneously. This would be a massive achievement in and of itself, but...

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...