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Light is very important to us. Without light, life on earth would not be possible. Light gives us heat, which we need in order to survive. The sun is our most important source of light, and without the sun, earth would be too cold to sustain life. To imagine how cold the temperature on the earth would be like if there was no sun, take a look at Pluto, the furthest planet away from the sun in our solar system. Scientists have predicted that the temperature of the surface of Pluto is below -200° C, because Pluto is so far away from the sun. Just think about it if there was no sun! Plants use light for photosynthesis, a process to make food when plants mix energy from the sun with carbon dioxide and water. If there was no light, plants would all crumble and die. Humans need plants for food and for other uses like medicine.
  
The sun is our most important source of light
We use light in our daily, everyday lives. Ancient man long ago made fire to make light and for warmth. As technology advanced, more people were using candles as a source of light to see during night time, since the sun could not provide the light. Lanterns were invented, but all these sources of light needed fuel to burn and to produce light. Mankind needed a more efficient and easier way of producing light during at night time. It was in 1879 when Thomas Alva Edison, along with his group of scientists, invented the electrical light bulb. He had tested thousands of materials, from metals to plants, in order to find the perfect filament material. Therefore, by the end of 1880, Thomas Edison invented a new type of light bulb that could last for around 1 500 hours. Then, in 1910, William David Coolidge invented the tungsten filament, which is still being used for filaments for light bulbs today.
The most common definition of light is visible energy that humans can see. Energy is not composed of matter, however, energy exists because it can cause changes in matter. Therefore, light is not matter, it is only energy. Light can travel very fast, it travels around 299 792 km per second in a vacuum (where there is no matter, like in space). In our atmosphere, light travels a little slower because there is more matter in which light must to travel across. In a liquid, light travels even more slower, and in a solid, light travels slowest.
Scientists in the past century have discovered how light is created. First of all, we know that all matter is made of very small building blocks called atoms. Atoms are made of a nucleus, which is made up of a number of neutrons and protons. The nucleus have really small objects orbiting around them, called electrons. The electrons have a path of orbit called its shell. Light is made when the electron jumps from one shell to another shell and becomes a photon. The electron then jumps back to its original shell and light is created.
Light is created when an electron jumps from one shell (path of orbit) to another and then back to the original shell.
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