200,000 kilometers per second

In air, glass, water and many other transparent materials, red light travels faster than blue light.

Red light will travel faster through a dispersive or refractive medium because it is bent less than blue light. Blue light travels slower through glass or water. This is because its shorter wavelength interacts more with the atoms and molecules, and is effectively absorbed and re-radiated.

Red light

Violet light

Explain that unlike sound, light waves travel fastest through a vacuum and air, and slower through other materials such as glass or water.

Yes. Light is slowed down in transparent media such as air, water and glass. The ratio by which it is slowed is called the refractive index of the medium and is always greater than one.

Albert Einstein’s special theory of relativity famously dictates that no known object can travel faster than the speed of light in vacuum, which is 299,792 km/s.

Time ran slower for the moving clocks just as Einstein predicted. So the faster something travels, the more massive it gets, and the more time slows – until you finally reach the speed of light, at which point time stops altogether. And so nothing can travel faster than the speed of light.

Special relativity states that nothing can go faster than the speed of light. If something were to exceed this limit, it would move backward in time, according to the theory.

Light is composed of photons, which have no mass, so therefore light has no mass and can’t weigh anything. Because photons have energy — and, as Einstein taught us, energy is equal to the mass of a body, multiplied by the speed of light squared.

A scientist named Karl Schwarzschild , discovered that, in a black hole, space-time can be so extremely curved that any light following this curvature cannot escape but, instead, doubles back on itself. This is why light cannot escape from a black hole. In a black hole the gravity is so great light cannot escape.

A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe directly.

Answer: Within the event horizon of a black hole space is curved to the point where all paths that light might take to exit the event horizon point back inside the event horizon. This is the reason why light cannot escape a black hole.

Universe’s oldest known quasar discovered 13 billion light-years away. Astronomers have found the farthest known source of radio emissions in the universe: a galaxy-swallowing supermassive black hole.

The half-life of xenon-124, one isotope of xenon, was recently measured to be a trillion times longer than the age of the universe! This is the slowest process ever measured by direct observation.