Why does heat wipe out a magnet?

This week we ask whether we're about to start spoiling other planets with our space forays, if there is antimatter in the human body, what causes cluster headaches, whether microwaving can ripen avocado, what causes long-sight, how atomic clocks operate, the basis of entropy and thermodynamics, why heat wipes out a magnet, and whether cleaning surfaces is a good idea for combating Covid-19...