Solar Furnace
A solar furnace is whatever optical device lets you collect the irradiant energy from the Sun and concentrate it to heat up things. The simplest example is the magnifier. On a sunny day, it is easy to burn things by focusing the light of the sun with a magnifier.
The principle is very simple: the action of a magnifier is to bring the object closer. One thus feels what it would it be to have the Sun so many times closer to us.
