LIGHT AND DARK

Praise God who created the heavens and the earth, and established darkness and light. But those who do not believe in their Lord give Him equals. (Qur'an, 6: 1)

We all know that without light, no one can see with the naked eye what surrounds it. However, the light we can see is only a very small part of the electroluminescent energy. There are other kinds of electroluminescent energies that humans can not perceive, such as infrared, ultraviolet, x-ray and radio waves. Indeed, these light waves can not be perceived by the human eye.

It is therefore interesting to note that the word "darkness" is still used in the plural in the Qur'an. The Arabic word dhouloumaat is used in the plural form in 23 different verses, and at no time is this term used in the singular. The use of the word "darkness" indicates that in addition to these visible light waves, there are other types of waves that we can not see.

Only recently have scientists discovered the rationale for this plural form. The wavelengths vary according to a form of energy known as electromagnetic radiation. All forms of electromagnetic radiation behave like waves of energy in space. This can be compared to the waves that form on the surface of the water when throwing a stone. Just as the waves formed on the surface of the water can have different sizes, the electromagnetic radiations can have wavelengths of different sizes.

Stars and other light sources do not all have the same kinds of emissions. These different rays are classified according to their wavelengths. The wavelength spectrum is rather wide. The difference in wavelength between the gamma rays, having the shortest wavelength, and the radio waves, having the highest wavelengths, is 1025. Almost all the rays emitted by the Sun are concentrated on only a small part of the light spectrum.

In order to better grasp the colossal dimensions of this figure, it would be useful to make a comparison. If we wanted to count to 1025 and if we did it day and night without stopping, it would take us 100 million times more time than the age of the Earth to reach that figure. The different wavelengths of the Universe are distributed according to a spectrum which is precisely of this size. 70% of the wavelengths emitted by the Sun are limited to a very narrow spectrum, between 0.3 micron and 1.5 micron. There are three kinds of lights inside this band: visible light, infrared light, and ultraviolet light.