Plank's Law
Plank's Law determines the emission pattern spectra of electromagnetic radation of a blackbody as a function of it's wavelength and temperature.
Plank's Law
Planks law shows that as the temperature of a body rises the peak of the emitted radiation shifts toward shorter wavelengths (figure 1)The peak of the sun's radiation is in the visible part of the electromagnetic spectrum and the earth's peak of radiation is in the thermal part of the electromagnetic spectrum.
(Figure 1: http://www.universityphysics.com/UniversityPhysics/plank_law3.htm)l