What is Cold? How cold is cold? It all depends on who is talking. To us ordinary people nothing in the world maybe so cold as failing through the ice on a frozen lade, or huddling(卷缩)on a windswept mountain hoping to be rescued in the dead of winter. Some may even think they are freezing to death when rushing under an ice-cold shower just out of a warm bed. Indeed, we all know what cold means. Arctic(北极) .explorers would laugh at such ideas. Down in the Antarctic(南极), where scientists of many nations spend very dark months living on a sheet of ice two miles thick, the temperature spends most of its time at 50or60 degrees Fahrenheit below zero, often with hundred-mile winds and heavy snowstorms. This is the cold that is cold, to them. Space people have still another standard. The coldest place in which a person can live and survive is some 400 degrees hotter than space itself,'. However, the coldest place in earth-colder even than space-is inside a machine called a cryostat(低温保持器). Here, scientists and engineers in thousands of laboratories and factories in many parts of the world regularly make cold that turns the South Pole's worst into a pleasant summer day. They are inching toward such cold that there is no temperature at all-down a frozen valley that leads to Absolute Zero, 459.67 degrees Fahrenheit below our zero of a cold winter's day. According to the passage, nothing is so cold to an ordinary person as ______.