This site has been created so that I can experiment with the Stefan Boltzmann constant. On the home page you will find a place to enter the power of an object and a distance from it, and the Javascript will calculate the energy flux and temperature in that vicinity.
It's a fairly simple calculation but it fascinates me. Of particular interest is the similarity between the energy present just 3 inches from a 100W light globe and the density of energy just above the Earth's atmosphere.
Just for the sake of convenience I'll list some numbers below which you can enter: