How could the light started? 

What is light? - An overview of the properties of light.

Visible light or light usually refers to electromagnetic radiation that can be detected by the human eye. The entire electromagnetic spectrum is very broad, from low-energy radio waves with wavelengths measured in meters to high-energy gamma rays with wavelengths less than 1 x 10-11 m.Electromagnetic radiation, as the name suggests, describes the fluctuation of the electric field. And a magnetic field, which transmits energy at the speed of light (which is ~ 300,000 km / s through vacuum). In addition, light can be described as a photon stream, a massless energy packet, each traveling with properties that are Waves at the speed of light A photon is the smallest (quantum) quantity of movable energy and is the realization that light travels in a discrete quantum, the origin of quantum theory.

The visible light does not differ from other parts of the electromagnetic spectrum, inherently, except that the human eye can detect visible waves. In fact, this corresponds to only a very narrow electromagnetic spectrum window, from about 400 nm for purple light to 700 nm for red light. Radiation below 400 nanometers is called ultraviolet (UV) and radiation longer than 700 nanometers is called infrared (IR). Both of these cannot be detected by the human eye. However, more advanced scientific detectors such as those produced by Andor can be used to detect and measure photons in a much wider range of the electromagnetic spectrum, and also reduce photons at much lower amounts. (Eg, light levels that are much weaker) than the eye can detect.

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