Thanks for the reply.  I know that you wrote that Dr. Butler will be explaining this in much more detail in the next post, but I did have another question I was curious about, based on what I read yesterday after posting my question (to try and get my head around this topic):

Does this process involve heat transfer and/or changes in pressure?  If so, how do they change with altitude?

Thanks for reading this and for answering my question.  I look forward to reading the next post.