If scientists understand hot and cold completely then high temperature superconductivity will become a reality and cold fusion is just child play. Until then, we can do all the theorizing we want but to really understand the universe we must understand what is hotness and what is coldness. The interiors of the stars is extremely hot. The vacuum is extremely cold. And yet they coexist in such discrete boundary. While human beings can be kept alive at merely 98.6 degrees. A few degrees (+/-) deviation will cause almost instant death.