# How Fast is the Speed of Light?

Light is what helps us see. We can even see a distant object like the famous Andromeda Galaxy situated two million light-years away from the earth. The difference between this galaxy and the cities we see on our television is that we can visit these cities one day if we wish but we will never visit the Andromeda Galaxy because of the distance. The fastest rocket currently travels at a speed of 30,000 miles per hour and even if we improve with time to the speed of light, it will still take us two million years to arrive at the Andromeda Galaxy.

## How Fast is the Speed of Light?

To our surprise, the light that enables us to see the Andromeda Galaxy left the galaxy two million years ago before even the human species evolved. The period between the time when the light was emitted and when we see it is called lookback time. Therefore, the speed of the light denoted by letter "c" is 299,792,458 meters per second to be precise. The photons that constitute light have no rest mass, and therefore they always travel at this speed, hence the formulation of the name “speed of light” represented by letter "c". As by the special relativity and the experiments that support it, the speed of light is similar to all standing observers.

## Constancy of the Speed of Light

The question is “Who gave the General Conference of Weight and Measures (CGPM) the right to outline the speed of light and using the meter as a unit of measurement?” The answer to this question is found in the fact that the speed of light in a void space is a universal constant and hence give every observer the right to use "c" to denote the speed of light. The steadiness of the speed of light has been put into use especially in physics. For example, the derivation of Maxwell’s equation has shown some hint that "c" must remain constant.

## Why Is Speed of Light Deemed to Be the Ultimate Speed Limit?

There is no other object with the same speed as light, and therefore the speed of light has been taken as the ultimate speed limit. Any huge object can project at a speed close to that of light but will not achieve it. This scenario has been explained by relativity which stipulates that an infinite quantity of energy is needed to power the object to that speed of light. However, atom’s parts with no mass are the only that can move at the speed of light. The suggestion of the presence of the tachyons, the ‘faster-than-light particles’ has been made. And if indeed they existed, an infinite quantity of energy is needed to ‘slow them down’ relatively to the speed of the light.

## How Is the Speed of Light Measured?

Many individuals have come up with ways of measuring the speed of light using different methods. K. M. Everson and others advanced the modern and accepted technique for determining the speed of light. It utilizes the separate measurements of frequency and wavelength discharged by a steadied laser. The method produced the speed of the light to be 299,792,458 meters per second with an error of plus or minus one meter per second.

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