THE SUN The sun in the center of our solar system and is the only brightest star around which all the planets revolve in a definite pathway. The sun that rises in the eastern horizon every morning and sets in the western sky giving SUN SHINE to the life on earth for almost 12 hours continuously around the world at different times for past 4.6 billion years. The sun that has power to produce visibility through the dark clouds, through the rain, through the fog and the mist ensuring the truthfulness of its duty. To any normal human being, this is what she or he can observe for the SUN. Yes ! a simple question that how and why does the sun shine and how does the light reach earth from the sun? So to understand this invisible science, we need to know the fact that sun is, a gas giant made up of primarily hydrogen and helium gases. The hydrogen gas has the atoms in the ion form, that these fuse / combine together to form bigger ion which is helium. This combining of hydrogen ions to form helium ion is via nuclear reactions. In doing so, the energy is released in the form of electromagnetic radiations made of PHOTONS [energy packets] that travels in the form of waves as electromagnetic radiations for 150 million km [also known as 1 astronomical unit or 1 AU ] and reaches earth in just 8.3 minutes. Now imagine: The circumference of the earth in 40,075 km. Suppose if we fly around earth in a plane at a speed of 1000 km / h, then how much time do we need to cover the distance? Is it almost 400 hours approximately??? Yes ! You are right! Now imagine traveling for 150 million km! That too in just 8.3 min! Isnt it crazy! I cannot even imagine this roller coaster ride because I have to be that one little tiny photon that will travel along with the others in a wave in such a high speed! Let us understand again the journey of sun rays. As the electromagnetic radiations (made of photons [ENERGY PACKET] that originated from the fusion reactions of hydrogen ions) travels from the sun, these get segregated into different frequencies. [Frequency of a wave ! Number of waves that pass any given point at any given time. A HIGH FREQUENCY: More number of wave passing through any invisible point, HIGH IN ENERGY WITH SHORT WAVE LENGTH. A LOW FREQUENCY: OPPOSITE!!!] [Wavelength: When a wave propagate in a direction it forms two phases. The phase above the direction of propagation of the wave is known as crest and the one below is trough. The distance between two consecutive crests or two consecutive troughs is known as wave length] So, these electromagnetic waves travelling with different frequencies thus form ELCTROMAGNETIC SPECTRUM. These waves are now known with different names based on the frequencies and we know and observe them in our day today life. Don't we? THE UNSEEN SUN RAYS Now we know the bunch of sun rays that we see are the visible rays and those unseen we know by different names and have been used in various applications. These rays are unseen rays but we observe them operating in our day today life. 1. Gamma rays: Used to treat cancer and kill microbes. 2. X-rays: Well known for detecting fractures in our body, detecting defects in rubber based products such as tyre and metals. Also, used for identifying the structure of chemical compounds. 3. Ultraviolet rays: These rays have bee n used for lamps, in photography, also used in light cancer treatment and are responsible for sun burn. 4. Infrared rays: The infra-red radiations have found its applications in thermal imaging cameras, remote control, fiber optic cables, electric cooker and many more. 5. Microwave rays: We use microwave in our kitchen to heat or cook food. Its microwave radiations that helps us in the cooking. 6. Radio waves: Widely used radiofrequency waves across the world for communication. [No radiowave then no communication, no tv programs to watch, no radio stations to hear, no WiFi] Does 100% of sun rays or solar radiations reaches earth? Then what is solar energy budget for earth? The answer to the first question is NO. Not 100% sun rays reach earth. The sun rays budget can simplified as below. 49% of the sun rays are reflected back to the sky by 1. Atmosphere (~ 6%) 2. Clouds (~20%) 3. Earth's surface (4%) Only 51% is absorbed by the oceans and land on the earth. It is indeed interesting to note that even this percentage is reflected to the space by the following 1. As a latent heat by the clouds. 2. Direct reflection from the earth's surface. 3. Conduction and rising air. Finally, what rays of sun actually reach earth's surface? The rays that constitute 51% are primarily rays that form visible window (so that we can see our beautiful world and colours of nature), radio waves (so that we can watch tv, listen to radio, communicate over mobile and landline, scroll through internet pages) . Part of ultraviolet (that could tan our skin on a sunny day), part of infra-red rays (the heat rays / thermal rays). Conclusion: THE INVISIBLE SCIENCE OF THE SUN-RAYS The invisible science of sun rays that can make hear each other from miles away and of course make you feel hot. The visible wave [optical window] is makes us see our beautiful world.