Does anything travel faster than the speed of light?
No. The speed of light is a natural limit. Nothing can move faster and light cannot move slower, even through materials. Light always travels at the same speed. The speed of light (usually denoted c) is a physical constant. Its value is exactly 299,792,458 meters per second. When light enters materials, its energy is absorbed. In the case of transparent materials, this energy is quickly re-radiated. However, this absorption and re-radiation introduces a delay. As light propagates through dielectric material it undergoes continuous absorption and re-radiation. Therefore when the speed of light in a medium is said to be less than c, this should be read as the speed of ENERGY propagation at the macroscopic level is less than c. At an atomic level, electromagnetic waves (light) always travel at c in the empty space between atoms. How can the speed of light be measured exactly? In 1983, the meter was redefined in the International System of Units as the distance traveled by light in vacuum
