Astronomers have witnessed a monster supermassive black hole erupting with a light-year-long jet traveling at one-third the speed of light.

"You cannot go at the speed of light, given that you have a finite mass," Pravica said. Einstein's theory of special ...

The speed of light is determined by the medium (material) through which the light is travelling. Light travels faster in a vacuum than it does in any other medium. Light changes speed as it passes ...