What is the speed of light?
We know that light travels in waves. These waves are not of the same wavelength. Some wavelengths are longer than others. However, all waves move at exactly the same speed in a vacuum.
When we talk about the speed of light, we are referring to the speed at which light .
travels. This is now defined as .9,792.458 km per second in empty space.
To get an idea of how fast this is, light can travel about seven times around the Earth in one second! Astronomers use the speed of light to measure how far away things are in space. They use a unit called the light year, which is the distance that light can travel in one year.
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