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How is light made?

A close-up of a halogen light bulb. Inside it is a filament, a thin wire wound in a tight coil. It is made of a metal called...Read More >>A close-up of a halogen light bulb. Inside it is a filament, a thin wire wound in a tight coil. It is made of a metal called tungsten. When electricity passes through the coil, the filament becomes white hot. The bulb gives off light.During the day, the world is lit by light rays from the Sun. Light is only one kind of energy which the Sun produces (heat and ultraviolet radiation are among the others). Light usually comes from very hot things: the Sun, fire, or the tiny wire inside electric light bulbs. But it can also be made by chemical reactions in some animals.



An illustration showing different sources of light. These are: moonlight (reflected sunlight), glow worms in a bush, and light...Read More >>An illustration showing different sources of light. These are: moonlight (reflected sunlight), glow worms in a bush, and light produced by electricity—torches, car headlights and a ship's lights


 

It takes more than eight minutes for light to reach us from the Sun.

The speed of light

Light travels at 300,000 kilometres (186,000 miles) per second. We do not notice light moving over short distances: when we flick a switch, light appears to fill the room instantly. But over long distances in space, light takes time to get from one place to another. It takes more than eight minutes for light to reach us from the Sun. 

If you could travel at the speed of light, you would be able to run around the world eight times in the time it took to turn on a light switch.

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