speed of light
We explain what the speed of light is and what it is for. Also, the story of its discovery. Its importance in different areas.
The speed of light is a universal constant, invariable in physical time and space.
What is the speed of light?
The speed of thelight It is a measure stipulated by the scientific community, generally used by the fields ofscience of physical and astronomical studies. The speed of light indicates the amount of distance that light travels, per unit of weather.
It is fundamental for the study of celestial, astronomical bodies, to know how is their behavior 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 for 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, invariable in time andspace physical. Its value is 299,792,458 meters persecond , 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 a year.
The speed of light that we have presented is the speed it has in a vacuum. However, light is transmitted by other means, such as water, glass, or air. Its transmission depends on certain characteristics of the media, such as electrical permissiveness, magnetic permeability, and other electromagnetic characteristics. There are then physical areas that electromagnetically facilitate its transmissibility and others that hinder it.
Understanding the behavior of light is not only important for astronomical studies, but also for understanding the physics they work with, for example satellites orbiting the Earth.
History of the speed of light
The Greeks were the first to write about the origin of light and itsthought It consisted in that the light emanated from the objects and then the human vision was emitted to capture it.
Until the seventeenth century, light was not considered to travel, but was conceived as an instantaneous phenomenon. However, this changed as of theobservation 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 with luck and some not, however all these physical studies in this incipient scientific age were pursuing the objective of measuring the speed of light even with the complications that his instruments and methods were inaccurate and primary.Galileo Galilei was the first to carry out an experiment to measure this phenomenon, but he did not obtain results that would help to calculate the transmission time of light.
Ole Roemer was the first to attempt to measure the speed of light in 1676 with relevant success. Roemer detected, by studying the planets, the terrestrial shadow reflected on the body of Jupiter, that the time between eclipses was shorter when the distance to the Earth decreased, and vice versa. It 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.
A wide variety ofmethods To improve measurement accuracy, for example, in 1958 the scientist Froome reached the value of 299,792.5 kilometers per second using a microwave interferometer, the most successful. As of the year 1970, the 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)
- Empty - 300,000 km / s
- Air - 2999.920 km / s
- Water - 225,564 km / s
- Ethanol - 220,588 km / s
- Quartz - 205.479 km / s
- Crown glass - 197,368 km / s
- Flint glass - 186,335 km / s
- Diamond - 123.967 km / s