When the speed of light depends on its direction

When the speed of light depends on its direction: Technological progress has now made it possible to detect these effects in a gas (in this instance nitrogen). To observe them, researchers from CNRS designed an optical cavity in which the light beams pass through a device comprising magnets and electrodes, which makes it possible to generate intense electric and magnetic fields (the applied magnetic field is 20,000 times greater than that of the Earth). In this way they succeeded in demonstrating experimentally, for the first time, that light does not travel at the same speed in opposing directions in a gas where an electromagnetic field reigns. The measured difference in velocity is around one billionth m/s (i.e. 10-9 m/s, which is equivalent to 10-18 times the speed of light).