Speed of light special theory of relativity, in which the speed of light in vacuum "c" featured as a fundamental constant, also appearing in contexts unrelated to light. This made the concept of the stationary aether (to which Lorentz and Poincaré still adhered) useless and revolutionized the concepts of space and time. In the second half of the 20th century much progress was made in increasing the accuracy of measurements of the speed of light, first by cavity resonance techniques and later by laser interferometer techniques. These were aided by new, more precise, definitions of the metre and second. In 1950, Louis Essen
Synchrotron-Light for Experimental Science and Applications in the Middle East the current director and former vice-president of SESAME. Synchrotron light (also referred to as synchrotron radiation) is radiation that is emitted when charged particles moving at speeds near the speed of light are forced to change direction by a magnetic field. It is the brightest artificial source of X-rays, allowing for the detailed study of molecular structures. When synchrotrons were first developed, their primary purpose was to accelerate particles for the study of the nucleus. Today, there are almost 60 synchrotron light sources around the world dedicated to exploiting the special qualities, which allow it to be used across a