The speed of light depends on the direction

Light does not go at the same speed in all directions under the influence of the electromagnetic field. Although it has been theoretically predicted, this first counterintuitive effect has been proven experimentally by a research team from France in a gas.

The researchers measured the difference between the speed of light spread in one direction and the opposite direction with absolute accuracy, about a billionth of a second. This result opened up new directions for more in-depth research aimed at improving the basic particle interaction simulation model. The study, published in this issue of Physical Review Letters , also points to new applications in optics.

In absolute vacuum, light travels at a constant speed of 299,792,458 m / s. It seems obvious that light will spread at the same speed in all directions. However, contrary to intuition, there are cases where this characteristic is not true, especially when there are electric and magnetic fields present. These first cases were theoretically predicted in the late 1970s and were observed in a vacuum. However, these very small changes are difficult to verify by experiment.

Technological advances today can help detect these effects in gases (in this case nitrogen). To observe them, the researchers designed an optical resonance device in which the beam of light passes through a device and the electrode produces an extremely strong electromagnetic field (the magnetic field is 20,000 times stronger. compared to Earth's magnetic field.

In this way, for the first time, they proved successful by experimenting that light does not go at the same speed in opposite directions in the gas with the presence of electromagnetic fields. The measured velocity difference is about 1 part per billion second (equivalent to 10-18 times the speed of light). The extremely small difference was predicted according to this theory caused by electromagnetic fields.

These results open up many new directions. First, researchers may have anisotropic measurements of light propagation to be extended even further. By increasing the sensitivity of the measuring device, one can observe the minute discontinuity of Lorentz immutability, the basic symmetry expressing part of relativity.

This may also help test some theoretical suggestions to improve the standard model (which is now being used to simulate all interactions between elementary particles). Secondly, the anisotropy due to that electromagnetic field can open many new applications in optics as parts behave differently depending on the direction; Everything is controlled by a magnetic field.