1) What temperature is in vacuum?
Is it 0 K?
2) What will happen when we put an object that has a room temperature to a vacuum? Will its temperature change ?
Full Version: Some questions...
1) Pretty close - but a perfect vacuum is impossible to achieve. Even deep space has a few atoms / cm^3. Also, with whatever object your doing a measurement on, you must shield it (and the thermometer) from ALL forms of radiation.
2) If the object is shielded from all forms of energy (impossible to do) and in a near perfect vacuum (to eliminate heat transfer through convection), then the object will slowly cool by emitting radiation (such as infrared) to near absolute zero. Even with perfect shielding and a perfect vacuum, hitting EXACTLY 0 °K may be impossible to reach, because space is not really as empty it seems. Particles can suddenly appear, then disappear which can thermally agitate any atoms nearby. Gravity is constant but can ripple (from such events as two black holes merging), which could add heat by the stretching / compressing of an object...or even space itself.
We can get very close to absolute zero now. Boise Einstein condensates are within a millionth of a degree above 0 °K.
SCIENCE!
xen-uno
2) If the object is shielded from all forms of energy (impossible to do) and in a near perfect vacuum (to eliminate heat transfer through convection), then the object will slowly cool by emitting radiation (such as infrared) to near absolute zero. Even with perfect shielding and a perfect vacuum, hitting EXACTLY 0 °K may be impossible to reach, because space is not really as empty it seems. Particles can suddenly appear, then disappear which can thermally agitate any atoms nearby. Gravity is constant but can ripple (from such events as two black holes merging), which could add heat by the stretching / compressing of an object...or even space itself.
We can get very close to absolute zero now. Boise Einstein condensates are within a millionth of a degree above 0 °K.
SCIENCE!
xen-uno
1) The temperature of vacuum doesn't exists, because temprature is defined for matter only. Vacuum has no temperature.
2) If you put an object in vacuum, when the thermal balance is reached, the object is at the temperature of the thermal radiations (infrared and around infrared electromagnetic waves) that fill the vacuum.
In vacuum, the heat can't be transmitted by convection or conduction, because there is no hard support for them. Heat is only transmitted by radiations.
Thus if you isolate an object at the room temperature into perfect vacuum, for example in a glass bottle, it will grossly stay at the room temperature because of the radiations exchanged through the glass. In reality it can be at higher temperature, especially in the sun, because of greenhouse effect : non thermal radiations can come into the bottle, they are converted into thermal radiations by the object, then these thermal radiations can't get out because glass don't let them out.
If the bottle is opaque, it doesn't change much : the bottle is at room temperature, thus emits radiations inside of itself. However, this slows down thermal exchanges very much. In a thermos flask, there is an internal container that doesn't toutch the external one. The air between them conducts little, and cold or hot liquid stored inside are very slow to take the external temperature by the little points of contact, and by radiation.
In the outer space, where there is no star to heat objects by radiation (if we discard planets, that have an internal source of heat, we can consider comets, that evaporate when they come near the sun and get heated), the final temperature of an object left alone will be 2.7 °K (-270.5 °C), because this is the temperature of the radiation that flows throughout the whole universe. It comes from the Big Bang, and has become very cold because of the universe expansion.
2) If you put an object in vacuum, when the thermal balance is reached, the object is at the temperature of the thermal radiations (infrared and around infrared electromagnetic waves) that fill the vacuum.
In vacuum, the heat can't be transmitted by convection or conduction, because there is no hard support for them. Heat is only transmitted by radiations.
Thus if you isolate an object at the room temperature into perfect vacuum, for example in a glass bottle, it will grossly stay at the room temperature because of the radiations exchanged through the glass. In reality it can be at higher temperature, especially in the sun, because of greenhouse effect : non thermal radiations can come into the bottle, they are converted into thermal radiations by the object, then these thermal radiations can't get out because glass don't let them out.
If the bottle is opaque, it doesn't change much : the bottle is at room temperature, thus emits radiations inside of itself. However, this slows down thermal exchanges very much. In a thermos flask, there is an internal container that doesn't toutch the external one. The air between them conducts little, and cold or hot liquid stored inside are very slow to take the external temperature by the little points of contact, and by radiation.
In the outer space, where there is no star to heat objects by radiation (if we discard planets, that have an internal source of heat, we can consider comets, that evaporate when they come near the sun and get heated), the final temperature of an object left alone will be 2.7 °K (-270.5 °C), because this is the temperature of the radiation that flows throughout the whole universe. It comes from the Big Bang, and has become very cold because of the universe expansion.
Thanks guys 
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.