Temperature is a measure of the extent to which molecules in a substance move around.
Substances emit electromagnetic radiation depending on their temperature, to the fourth
power.
It follows the equation P over A equals epsilon times omicron times T to the forth power,
where P equals power equals energy per unit time in watts, A equals area in meters squared,
epsilon equals emissivity which is efficiency of which a substance emits electromagnetic
radiation and ranges from a value of zero which is inefficient to a value of one which
is efficient.
Omicron equals Stefan-Boltzmann constant which is 5.67 times ten to the minus eight watts
per meter squared per degree Kelvin to the forth power.
At absolute zero, zero degrees Kelvin which is equal to minus 273 degrees Celsius, molecular
movement ceases and so does electromagnetic radiation.
For a less extreme example, take human beings.
In the parlays of physics, we are all behaved nearly like perfect blackbodies.
That means that people are almost ideal radiators having an emissivity of .98.
An average person has a surface area of about two meters squared and naked skin has a temperature
of about 32 degrees Celsius, or 305 degrees Kelvin.
Therefore, the net electromagnetic radiation from a naked person in a twenty degree room
is about 143 watts.
So, each of us is only slightly brighter than a 100 watt light bulb.
Well rest assured you differ from the light bulb, At least in respect to your spectral
qualities.
The wave length at which a substance emits the most electromagnetic radiation is inversely
proportional to its temperature.
It follows the equation, of Lambda sub max equal 2.8978 times ten to the minus third
meters.
A person with a skin temperature of 305 degrees Kelvin has a Lambda sub max of 9.5 times ten
to the minus six meters of wave length in the mid infra red.
For this reason camera sensitive to infrared radiation can capture the image of a person
in the dark.
The sun has an effective color temperature of 5,780 degrees Kelvin and emits a maximum
amount of energy at 5.01, ten to the minus seventh meters, a wave length that we perceive
as the color of green.
Over half of the electromagnetic radiation from the sun is in the wavelength from .4
to .7 micrometers that are visible to the human eye.
This is not happenstance.
Not only do particle waves with these wavelengths have energy suitable to well-behaved biochemical
reactions, but having an organ such as an eye that is most sensitive to the prevalence
of solar radiation serves surface-dwellers like us very well.
In contrast, cave-dwellers have no need for a human eye because their natural habitat
is to avoid solar wavelengths.
Earth acts approximately like a blackbody, with an effective temperature of about 287
degrees Kelvin or fourteen degree Celsius, and thereby emits a maximum amount of energy
at 10.1 micrometers, A wavelength that falls in the infrared.
Several gases in the atmosphere absorb some of the wavelengths that Earth emits.
In particular carbon dioxide, methane, and nitrous oxide are considered greenhouse gases
because they transmit the strongest wavelengths from the sun from .3 to one micrometer.
But they absorb major wavelengths emitted from the Earth from two to eight micrometers.
When gas molecules absorb infrared radiation, their vibration energy increases and so does
their temperature.
Warmer gas molecules emit electromagnetic radiation that's shorter, more energetic wavelengths
than cooler gas molecules.
Putting this all together, a volume of gas molecules emits long-wave electromagnetic
radiation proportional to its temperature.
When illuminated with electromagnetic radiation of appropriate wavelengths, some of the molecules
in the volume will absorb this energy and increase their movements.
Thru collisions of these molecules with their neighbors like a molecular mosh pit, movement
of the volume as a whole increases.
The gas volume therefore will increase in temperature and emit electromagnetic radiation
at wavelengths that are shorter than the gas volume emitted before illumination, but longer
than the incident radiation.
Energy is conserved because the energy in the shorter wave length electromagnetic radiation
absorbed by a few molecules equals the total energy in the longer wavelength radiation
emitted by many molecules.
In summary, certain internal forcing factors Orogeny epeirogeny and volcanism depend on
tectonic movements of earth's crust.
Albedo the percentage of solar energy reflected, varies widely among different natural materials
from 85 to five percent.
Earth exchanges energy with it's surroundings, in the form of electromagnetic radiation.
Number four; electromagnetic radiation can be characterized by its wavelength.
Five, over half the electromagnetic radiation from the Sun has wavelengths in visible spectrum
between 4 and 7 micrometers.
Greenhouse gasses in earth's atmosphere are transparent to visible light, but absorb in
the infared.