It's a beautiful day and you're outside enjoying the warm sunshine. A few minutes later a cloud moves over the sun and you feel a chill. After the cloud moves on you warm up again and continue enjoying your day.

It's obvious that the sun transfers energy when you feel it on your face. When the sun is shining on you the energy of the sun warms you. But, it's fairly common knowledge there are millions of miles of nothing, of near vacuum, between us and the sun. How does that energy get to us?

There are three methods of heat transfer between objects. One is conduction, that is when an object is in direct contact with another object and the heat is transferred. We see this when the handle on a pot on the stove gets hot. The heat is conducted through the metal of the pot to the handle, and further to your hand if you're careless. Another method of heat transfer is convection. Convection is the transfer of heat through moving fluids. When a breeze passes and we feel a chill that is from the movement of the air past our bodies transferring heat from us to the air.

But those two methods of heat transfer don't tell us how the energy of the sun warms our face. To explain that we need to explore radiation.

Radiation brings up scary thoughts of nuclear events, and that is related. But the idea of radiation is a broader concept. Radiation is simply the transfer of energy through electromagnetic waves. Some electromagnetic waves are very high energy and can be dangerous to life, that's where the scary stuff is. Radio is transmitted through electromagnetic radiation as well, however. And radio waves are fairly low energy and relatively harmless. Light is also an electromagnetic wave. In fact it is possible to consider all electromagnetic waves as a form of light, some we can see, which we call visible light, and some we can't.

Heat is transferred through electromagnetic waves that are of a particular energy level. Visible light has an energy level that the chemicals in our eyes detects and then sends signals to the brain. Radio waves are of an energy level that we can build antennas that detect those waves and convert the radio waves to movements of electrons that create electricity. When the radio waves are used in a particular way we can use that electricity to transmit information in the form of sound or television. Heat waves, or infrared light, is of an energy level that causes the molecules that they hit to increase their motion.

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