在真空中,有沒有溫度?!

The [temperature] that we hear everyday from weather reports is in fact the [air temperature], that is, it indicates the temperature of the medium - air, which we are living within.

Thus, [temperature] generally refers to the temperature of a medium. In vacuum, there is no medium (assume an idealized perfect vacuum), then [temperature of vacuum] seems has no physical meaning at all.

Just imagine if there is a closed room (with no windows) on earth, and we try to pump out all the air inside the room. [Air temperature] in the room then has no meaning as there is no air inside the room. However, if a thermometer is placed inside this airless room, the thermometer will still record a temperatue. This temperature is called the [radiant temperature]. Physically, it represents the radiant energy emitted from the walls of the room, which are at a certain temperature. Thus, radiant temperature measures the radiant energy (or photons, notice that these photons are not necessarily in the visible range, they could be in the infrared range, or in the microwave range, depending on the temperature of the walls)) present in a cavity. As long as there is radiant energy (photons), there is a temperature.

Photons of different frequencies are present in space. In space far away from any stellar objects, there is still photons present. There thus exists a temperature, the radiant temperature, in space. The magnitude of this radiant temperure depends on the number of photons and their energies present in a particular region of space.

As everybody knows that, according to the Big Bang Theory, there exit a microwave backgroung in the universe. The temperature (which is the radiant temperature) of which is 2.3 degrees K. This is the lowest temperature in the universe.

[Note: measurement of radiant temperature is by means of a black-body thermometer. It can be used to measure the ambient radiant temperature in our environment.]

回答者： 候選編號 001
回答時間： 2008-06-18 14:19:50


答者似乎不太了解物理？(其實我也只是文科生)
絕對零度是(-273度)
那時候,物理的任何運動(粒子運動、布朗運動)麵應該不復存在
因為:
溫度愈高=物理運動愈快/大=能量愈大

溫度是描述粒子的平均動能。

真空沒有粒子，因此其溫度也不能被定義。

First of all, the lowest temoerature is about -273 degree celcius, which is 0 K. K (degree Kelvin) is the absolute temperature.

Why we need to define an absolute temperature? Since temperature is the average energy of molecules, that is the higher the temperature, the higher average (kinetic) energy of the molcules/particles. so, the min. energy is all the molecules stopped, the min. temperature is 0K.

In a vacuum, there is no molecules, so there is no temperature. But in fact, there is no real vacuum, even the density is very very low.

Sometimes, we would say that in space, when we are shone by sun, the temperature (of our body) is very high (up to a few hundres degree K), when we are in dark, the temperature is very low (a few ten degree K). This is because there are molecules on our body, they can be heated up and cool down.

我認為溫度例如華氏、攝氏是一個測量和表示溫度的量值，就如數字符號一樣，這宇宙上沒有最大或最小，如果有一樣東西會發出很高的熱力，例如 90000℃，或很低的低到 -90000℃，都算是有溫度。

故可以說真空一樣有溫度，如真空熱水瓶內裡裝了滾水，外面都會和室溫一樣，並可保溫很久，這只是利用真空原理，不讓空氣產生對流和傳導把熱量帶走，利用抽真空的原理做出一種生活必需品。