0We are not discussing Black Holes. It goes somthing like this. Compress air in a bike pump the air will heat up, for you have done work compressing it, cool the bike pump and the air inside the pump and release the pressure on the plunger. The plunger won't return to the starting point till the expanding air is reheated. Now I understand the same principle applies to compressed liquids/ solids. Original state => Compressed => cooled then decompressed => must be warmed => Original state. There must be a warming phase to replace the heat lost during cooling to returm the material to it's original state. Please Register or Log in to view the hidden image!