看了楼上讲的负绝对温度之后很好奇 股沟了一下 看到NASA上面写的 负绝对温标 定义如下
只存在于指定的系统中（具有少量能级数）
负绝对0度比（某些）正绝对温度要高
具有负绝对温度的系统最终会冷却（或升温，取决于如何对待）至正绝对温度，即使它完全孤立与环境
大概是这样 原文如下 不知道翻译的对不对 细节可以参照原文 就不翻译了 我先仔细看看
Are there negative absolute temperatures? Sort of. Physicists have defined a negative absolute temperature, but it's a bit flakey, for these reasons:
it only applies to certain physical systems (those with a small number of energy levels),
Here's a bit more detail. Certain physical systems have small set of energy levels that they can be in. For example, a laser uses this principle. The atoms (or molecules) that produce the lasing effect can be in one of a number of energy states. Normally, only a small percentage of the atoms are in the highest energy states; many more are in the low energy states. Scientists have found equations that describe how many of the atoms are in which energy state. As you might imagine, these equations depend on temperature. The hotter the system, the more atoms are in the higher energy state. In fact, if you know what fraction of the atoms are in each energy state, you can plug that into the equation and solve for the temperature.
A laser operates by pumping energy into the atoms, pushing many of them into the high energy states. When the atoms drop back into the lower energy states, they give off the energy as a beam of laser light. But between the time they get pumped up and the time they drop back, they're in an abnormal state, with lots more atoms than normal in the high energy state. If you plug this abnormal distribution into the equation and solve for temperature, you may get a negative number.
Here are some websites that describe this idea in much greater detail:
Is there negative Kelvin temperature? (not a NASA site)
Positive and negative picokelvin temperatures (not a NASA site)
negative temperatures are hotter than (some) positive temperatures,
a system with a negative temperture will eventually cool down (or warm up, depending on how you look at it) to a positive temperature, even if it is insulated perfectly from its surroundings.
