ABSTRACT
Refrigeration has changed a great deal over the years. People have known for thousands of years that food stored in cool places or packed in snow would last longer than food not kept cool. Icehouses became popular in the 1800s and various insulating techniques for slowing the melting process were devised. Mechanical refrigeration took off in the middle of the nineteenth century as methods to compress a gas, such as ammonia, methyl chloride, or sulfur dioxide, circulate it through radiating coils, and then expand it were devised in America, Australia, France, and elsewhere. Educational technology draws on the work of multiple disciplines, multiple activities, multiple people, multiple tools, and multiple opportunities to facilitate meaningful change.
