What is light?
Light is a form of electromagnetic energy. It is produced by electrons that have gained extra energy from another source. This energy can be given off as heat or light. Light travels in waves of energy that consist of very tiny particles called photons. Atoms emit (give off) photons when heated to a high temperature. The extreme heat causes the atoms to collide with each other, and the extra energy is given off as light. The amount of energy released determines the colour of the light. The hotter an object, the more high-energy blue light is produced. As the object cools, the lower energy produces red light. When metal is heated to white hot, it gradually becomes red as it cools.
How fast does light travel?
The speed of light is the fastest speed known — light travels through the vacuum of space at 300,000 km per second. Nothing else can travel at this speed, and the theory of relativity, conceived by Albert Einstein, says that nothing can even approach this speed. This means that travel to the stars will not be possible, because it would take hundreds of years to reach them.
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