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Does a vacuum have an acual temperature?

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  • 17-04-2012 3:54pm
    #1
    bananarama22
    Banned (with Prison Access) Posts: 67 ✭✭


    When we say it's 20°C, we mean the air temperature is 20°C, of 293.15K (not the omission of the ° :D ) .. but how can temperature exist where there are no particles?? What if I brought a thermometer to space??

    What would happen to a digital probe thermometer??

    What would happen to a mercury/alcohol thermometer??

    The latter works on pressure, lower pressure = lower bioling point, so does that mean that no pressure = bioling at essentially 0 K ?? :confused::confused:
    So does that mean that the mercury in the thermometer would evaporate inside the tube :confused::confused::confused:

    Sorry for the ignorance, physicists are probably red in the face from all that facepalming :P


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    #2
    SOL
    Registered Users Posts: 1,155 ✭✭✭SOL


    http://www.boards.ie/vbulletin/showthread.php?p=69927839

    might be worth reading as I think it might begin to answer a lot of your questions.


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    #3
    Gurgle
    Closed Accounts Posts: 5,064 ✭✭✭Gurgle


    bananarama22 wrote: »
    What would happen to a digital probe thermometer??
    A digital thermometer works on the basis of voltage drop across a PN junction. In space I guess this will depend on the incident light. (They will also have a rated temperature range, within which the PN voltage drop is linear)
    bananarama22 wrote: »
    What would happen to a mercury/alcohol thermometer??

    The latter works on pressure, lower pressure = lower bioling point, so does that mean that no pressure = bioling at essentially 0 K ??
    It doesn't matter that its in a vacuum, its a sealed unit with a vacuum in there anyway. The mercury or alcohol will expand or contract depending on it's temperature, again dependent on incident light. Most likely the liquid will freeze in either case(-38° for mercury, -114°C for ethanol), unless its in direct sunlight.


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    #4
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Something I've been reading about recently; Unruh radiation.

    In the theory, if an observer is moving in relation to a vacuum, they will see radiation.

    Supposedly if you wave a thermometer around in a vacuum, it will register a temperature change from the Unruh radiation, because of its motion.

    I don't know enough about it to say the idea is wrong - but it sounds wrong.


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