Measuring Temperature using wavelenghts

[Aki]

I want to know the formula to find the temperature of outer space by measuring the wavelenghts of the electromagnetic radiation coming from that area. Does anyone know what I'm talking about?

[James R]

If you're talking about the cosmic microwave background radiation, the relationship you're looking for comes from the peak wavelength of the blackbody radiation spectrum. (I think this is sometimes referred to as Wien's law, but not sure.) Basically, the temperature is inversely proportional to the wavelength. The microwave background has a peak wavelength of about 1 mm, which corresponds to a temperature of 2.7 K.

[Claude Bile]

The law is called Wein's Displacement Law.

This equation (as well as some other related equations) are presented here;

http://www.rumford.com/radiant/formulas.html

Claude.