|Figure A: Radiation From the Sun Hitting Earth|
Unlike convection, radiation does not require any fluids in order to transport heat. The energy from the sun is one great example of radiation. The sun emits light in a broad range of wavelengths which all contain energy. These waves are also discussed in the climate section for energy balance. The waves are emitted from the sun and travel through space and hit the earth and other planets. Once the light waves hit the atmosphere and ground, the energy stored in the waves heats up the soil and air, allowing conduction and convection to occur and move energy around the earth/atmosphere system. [Note that this radiation is not the same as nuclear radioactivity, which is caused by transformation of atoms undergoing physical changes within naturally occurring rocks as well as nuclear power plants and bombs.]
|Figure B: Roasting Marshmallows by Radiation|
But the sun isnâ€™t the only thing that emits radiation. Radiation is given off by lightbulbs, fires, and anything that has a temperature. Even you glow, but in a wavelength that the human eye cannot see. All of us are brighter than we think!
One example of radiative heating is the fires that many homes used to (and may still do) use to keep warm during the winter. We donâ€™t have to touch the fire to feel its warmth (that would be conduction, and not recommended!). When we face the flames we feel the warmth of the fire on our faces due to the radiation being given off, even when we are too far away to feel the hot air blowing around the coals. Radiative heating from the sun warms the soil in spring and leads to the new growth of plants each year as seeds in the soil germinate.