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What do you think the air contains?

It contains millions of tiny, fast-moving particles.
Waves of energy pass through the air, too.
This kind of energy, called electromagnetic energy, is made of vibrations of electricity and magnetism.
There is a whole range of different electromagnetic waves.

Some electromagnetic waves vibrate very fast. These waves have a great deal of energy.
Other waves vibrate slowly and have less energy.
Some of the most energetic electromagnetic waves are called X rays. These are used in hospital machines to photograph the inside of a person’s body. When an X ray photograph is taken, your body receives a very short burst of X ray energy

The speed of electromagnetic waves

There are many different types of electromagnetic waves, but in one way they are all similar.
They travel through space at the same speed as light—186,282 miles (299,792 kilometers) per second. 

• Electromagnetic waves can travel around the world more than seven times in one second.
• When you watch a sports telecast that is a live transmission from 3,100 miles (5,000 kilometers) away, you are seeing the picture at almost exactly the same moment as the athletes are actually running.
• It takes about eight minutes for light waves from the sun to reach us on earth.
• Other stars are even farther away. It takes light waves about four years to travel from the closest stars to the earth. Scientists say that these stars are light years away from the earth.
• Light and heat energy travel through the air as different kinds of electromagnetic waves. 
• Sunlight travels to earth as light waves.
• The heat from the sun travels as infra-red waves.
• Radio waves bring us radio and television.