299,792,458 m/s

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 usually greater than one. When people talk about “the speed of light” in a general context, they usually mean the speed of light in a vacuum.

Originally Answered: What is the maximum speed a particle can move? H = 20,675 km/second per billion light years. At the edge of the observable universe, 46.5 billion light years (in any direction), this is 3.2 times the speed of light.

Light of different energies and wavelengths will interact with matter differently, have different indices of refraction, and therefore travel at different speeds through a medium other than vacuum. This is why c is often called the ultimate speed limit of the universe.

Nothing can travel faster than 300,000 kilometers per second (186,000 miles per second). Only massless particles, including photons, which make up light, can travel at that speed. It’s impossible to accelerate any material object up to the speed of light because it would take an infinite amount of energy to do so.

Special relativity In 1905 Einstein postulated from the outset that the speed of light in vacuum, measured by a non-accelerating observer, is independent of the motion of the source or observer.

Even if the fabric of space didn’t change over time, there are plenty of objects we can see today that could be farther away than 13.8 billion light-years. The only catch is that their light could travel for 13.8 billion light-years at most; how the objects move after emitting that light is irrelevant.