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Heat and space

  1. Jul 12, 2013 #1
    A mass of gas has its molecules moving. (Say in a jar)

    Another mass of gas has its molecules moving faster. This gas is hotter than the first one.

    So, heat is motion of molecules.

    Now, I take this mass of gas into deep space devoid of any gravitation.

    My questions are,

    1. Will this gas cool down. If yes, why?

    Let me give my detailed insight/conjecture.

    A body moving in uniform motion does not get affected by the extremely low temperature of deep space and continues its 'motion' unabated.

    Each molecule is in motion, even if not uniform motion.
    So, if the gas cools down, why does deep space affect the motion of molecules?

    2. Does deep space know the difference between uniform and non-uniform motion?
  2. jcsd
  3. Jul 12, 2013 #2


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    Not necessarily. If it has a different gas (with lighter particles), the temperature could be equal or lower.

    Heat is related to the motion of molecules.

    Does it have contact to the environment? Can it radiate, does it receive radiation?

    The uniform motion of a large object as a whole has nothing to do with its temperature.

    The gas can emit electromagnetic radiation (blackbody radiation) and cool down.

    Space does not "know" anything.
  4. Jul 13, 2013 #3
    Thanks for the insight.

    Plz explain how is heat 'not' motion of molecules but 'related to' motion of molecules.

    How to define contact?

    The molecules of the gas are colliding with the molecules of the jar. The molecules of gas have forces of attraction and repulsion operating between them. The molecules of the jar are also oscillating and vibrating. In fact molecules of jar are in immediate contact with the space.

    Would molecules of jar also slow down?

    Would the space that is inside the atoms/nuclei of the jar also cool down and in any way affect the motion of atoms/molecules/nucleons of the jar/gas?

    When does an object turn large? when we consider 2 atoms/molecules or more than 2?

    Suppose the large object enters the area of space having absolute zero temperature. Will its motion still remain unaffected by the temperature around it?

    Suppose a single CO2 molecule is moving in deep space away from any soured of gravity or radiation. What would be the scenario? Would the motion of oxygen atoms around the carbon atom slow down?

    Can't a single molecule of CO2 be taken as a large object when there is no object nearby with which to compare this CO2 molecule.

    Then how does space/nature see to it that the moment force is removed 'only' uniform motion results without fail.

    Do take pains to answer my questions. This is really a laborious job. Thanks in advance.
  5. Jul 13, 2013 #4


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    An apple is not a tree, but it is related to a tree.
    More about heat

    Some way to exchange thermal energy.

    If "gas+jar" cool down, sure.

    Empty space does not have a temperature.

    When you consider all molecules in an object, independent of the size of the object itself. Apart from that, all objects with ordered motion are "large" in that respect.

    Space does not have a temperature. The motion of the particle is always unaffected by empty space.

    No. Why do you think it could?
    Note that a single CO2 molecule does not even have a temperature.

    I don't understand that question.

    I get the impression that you should start with the basics (with a text book, not here), as I guess you have some fundamental misunderstandings, and it is impossible to resolve them if you just keep asking random questions.
  6. Jul 13, 2013 #5
    Thanks for your responses.

    But I am afraid to say that you haven't explained anything nor tried to do so.

    It seems to me that either you are irritated by such questions or you consider it below your standard to deal in such questions.

    BTW, I have studied all these concepts till 12th class from textbooks.

    I am under the impression that people on this forum can explain basics more lucidly that a textbook.

    Thanks again.
  7. Jul 13, 2013 #6


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    There is nothing wrong about mfb answers and I agree with his opinion that you probably have some fundamental misunderstandings about what the heat is. But it is difficult if not impossible to pinpoint where the problem lies just by reading your questions.
  8. Jul 13, 2013 #7


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    Not necessarily, and I think you may be confusing "heat" and "temperature". "Hotter" does not mean "has more heat", it means "has a higher temperature".

    One way to see that heat and temperature are not the same is to consider that if you add the same amount of heat to the same amount of different substances, you may not get the same temperature change (google for "specific heat" to see what I mean).
    Last edited: Jul 13, 2013
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