Speed of Light (Meaning and Explanation)

We explain what the speed of light is and what it is for. Also, the story of its discovery. Its importance in different areas.

What is the speed of light?

The speed of light is a measure stipulated by the scientific community generally used by the fields of science of physical and astronomical studies. The speed of light indicates the amount of distance light travels per unit of time.

It is essential for the study of celestial and astronomical bodies, to know what their behavior is like and the transmission of electromagnetic radiation and how light is perceived by the human eye.

If we know a distance, we can know how long it takes light to travel it. As an example, It takes about 8 minutes and 19 seconds for light from the sun to reach Earth. The speed of light is considered to be a universal constant, invariant in time and physical space. Its value is 299,792,458 meters per second, or 1080 million kilometers per hour.

This speed is related to a unit of length that is widely used in astronomy, which is the light-year which refers to the distance traveled by light in one year.

The speed of light that we have presented is what it has in a vacuum. However, the light is transmitted by other means, like water, glass or air. Its transmission depends on certain characteristics of the media, such as electrical permittivity, magnetic permeability, and other electromagnetic characteristics. There are then physical areas that electromagnetically facilitate its transmissibility and others that hinder it.

History of the speed of light

The Greeks were the first to write about the origin of light and his thinking was that light emanated from objects and then human vision was emitted to capture it.

Until the 17th centurylight was not considered to travel but was conceived as an instantaneous phenomenon. However, this changed after the observation of eclipses. It was only Galileo Galilei who, by carrying out certain experiments, questioned this principle of “instantaneity” of the distance that light travels.

Several experiments were carried out by different scientists, some lucky and others not, however all these physical studies in this incipient scientific era pursued the objective of measuring the speed of light even with the complications that their instruments and methods were inaccurate and primaries. Galileo Galilei was the first to carry out an experiment to measure this phenomenon but did not obtain results that would help calculate the light transmission time.

Ole Roemer was the first to try to measure the speed of light in 1676 with relevant success. Roemer detected, by studying the planets, from the Earth’s shadow reflected on the body of Jupiter, that the time between eclipses was shorter when the distance to the Earth decreased, and vice versa. He obtained a value of 214,000 kilometers per second, an acceptable number given the level of precision with which the distance of the planets could be measured at that time.

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Then, in 1728 James Bradley He also studied the speed of light but by observing the transformation of the stars, detecting the displacement that occurred in relation to the movement of the Earth around the Sun, he obtained a value of 301,000 kilometers per second.

A wide variety of methods have been used to improve the accuracy of the measurement, for example, in 1958 the scientist Froome reached the value of 299,792.5 kilometers per second using a microwave interferometer, the most accurate. Starting in 1970, measurement improved qualitatively with the development of laser devices that have greater capacity, great stability and use cesium clocks that improve the accuracy of measurements.

Speed of light in different media (medium-speed)