Yan Su

A radio signal travels from Mars to Earth, but on the way it has to push through the invisible "wind" of charged particles blowing from the Sun. This wind, like ripples on water, slightly distorts radio waves.

In an ordinary semiconductor, it is hard to get two things at once: strong magnetism and a tightly bound electron-hole pair that is born when light is absorbed. Magnetic impurities, which make a material magnetic, also prevent the electron and hole from staying together: they are like noisy neighbors that do not let the pair exist in peace.