Black Body Radiation

All objects radiate Em waves regardless of size and temperature. Most matter will emit IR waves naturally and hotter bodies will emit more.

Objects will vary the Em waves emitted depending on their temperature. The higher the temperature the greater the frequency emitted.

Here on Earth it is very rare to see any emissions above the IR region.

Black Body definition:

Black bodies are materials that absorb all radiation while not reflecting or transmitting any. This would mean that a black body is a perfect emitter and receiver.

It’s a perfect emitter as well because emission of Em waves and receiving are the same processes.

Thermal equilibrium occurs when an object emits radiation and absorbs it at the same rate. This means there is no increase in energy so there is no change in temperature either.

This is important in our understanding of the Earth’s temperature as it relies on many factors. Some of these factors  are the rate of absorption and emission of radiation the reflection of radiation from and into space.

For example, here on Earth we can use sunlight to heat our greenhouses and then the rate of loss matches the rate of absorption our houses would reach a constant temperature. But once night come we would emit all that energy back out and cool down.

Looking at our planet we can observe that the dark side of our planet receives reflected rays from the light side through our atmosphere and helps to keep it warmer than it otherwise would be.