Temperature in a vacuum?
Ira Hsu
Here's an [idle] thought:
What would be the temperature inside a vacuum? Or would there be a
temperature? I guess that inside a true vacuum, there would be no
moving particles; thus there could be no kinetic energy and no thermal
energy. If you stuck a thermometer in the vacuum and and put the vacuum
in a microwave, would you get a temperature reading? Since microwaves
can pass through a vacuum... right?
]| )__Ira Hsu ___iy...@columbia.edu ____http://www.columbia.edu/~iyh2
]|/_________________ /) '/ / __________________
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Charles Wm. Dimmick
Ira Hsu wrote:
>
> Here's an [idle] thought:
> What would be the temperature inside a vacuum? Or would there be a
> temperature? I guess that inside a true vacuum, there would be no
> moving particles; thus there could be no kinetic energy and no thermal
> energy. If you stuck a thermometer in the vacuum and and put the vacuum
> in a microwave, would you get a temperature reading? Since microwaves
> can pass through a vacuum... right?
Yes, but the reading of the thermometer is the reading of the
temperature of the fluid in the thermometer, not the reading of
the temperature of the vacuum. If my car sits outside on a sunny
but cold day the temperature in the car is much warmer than the
temperature of the air outside the car. If my car sat in a vacuum,
there would not necessarily be any relationship between the temp.
of the air in the car and the temp. of the vacuum.
Charles Wm. Dimmick
"...and some rin up hill and down dale, knapping the chucky stanes
to pieces wi' hammers like sae mony road-makers run daft -- They say
it is to see how the warld was made!"
DaveHatunen
In article <3367B0...@columbia.edu>, Ira Hsu <iy...@columbia.edu> wrote:
>Here's an [idle] thought:
> What would be the temperature inside a vacuum? Or would there be a
>temperature? I guess that inside a true vacuum, there would be no
>moving particles; thus there could be no kinetic energy and no thermal
>energy. If you stuck a thermometer in the vacuum and and put the vacuum
>in a microwave, would you get a temperature reading? Since microwaves
>can pass through a vacuum... right?
There is no temperature in a true vacuum.
If you put a thermometer in a true vacuum it is no longer a true vacuum
(in a certain sense). A thermometer displays its own temperature, which
is presumed to be the temperature of the object being measured. But in
a true vacuum there is no object to measure, so the thermometer will
reach an equilibrium temperature due to radiation absorption and
emission and display that temperature. An ordinary thermometer is so
massive that it will do likewise in a high, but not true, vacuum.
although the widely spaced molecules of gas are at sufficient velocity
to be at thousands of degrees celsius.
Micro could be one of the radiations emitted and absorbed, and, in
space, are. That temperature cannot be determined easily, a priori.
--
*********** DAVE HATUNEN (hat...@netcom.com) ***********
* In the land of the blind, the one-eyed man is king... *
* Until they find out he can see, then they kill him *
*********************************************************
Karl Brace
Ira Hsu wrote:
> Here's an [idle] thought:
> What would be the temperature inside a vacuum? Or would there be a
> temperature? I guess that inside a true vacuum, there would be no
> moving particles; thus there could be no kinetic energy and no thermal
> energy. If you stuck a thermometer in the vacuum and and put the vacuum
> in a microwave, would you get a temperature reading? Since microwaves
> can pass through a vacuum... right?
Charles Wm. Dimmick wrote:
> Yes, but the reading of the thermometer is the reading of the
> temperature of the fluid in the thermometer, not the reading of
> the temperature of the vacuum. If my car sits outside on a sunny
> but cold day the temperature in the car is much warmer than the
> temperature of the air outside the car. If my car sat in a vacuum,
> there would not necessarily be any relationship between the temp.
> of the air in the car and the temp. of the vacuum.
I agree with Charles. To elaborate, a thermometer measures the
temperature of ITS OWN working fluid or bimetalic strips or
electro-resistive filaments, or whatever mechanism it relies on. This
is SOMETIMES a good measure of the surrounding temperature, but not
always. Let's assume a mercury thermometer inside glass. The
temperature of the mercury depends on energy radiated to it (infra-red,
microwave, visible, etc), energy it radiates away, and conduction and
convection with surrounding materials. In typical applications
convection/conduction dominate, and the mercury measures the temperature
of the surrounding fluid or gas fairly well. If you add sunlight,
radiated energy becomes significant and it will read high. Expose it to
a clear night sky and it will radiate away some of its heat and will
read low (this is why you can get frost on the grass even when the air
temperature is above freezing). In a vacuum, the ONLY effect on the
temperature of the mercury is radiation, and it will warm up or cool
down enough that it absorbs and radiates the same amount to its
surroundings. If you have an opaque, uniform-temperature vacuum
chamber, the mercury should eventually read the temperature of the walls
of the chamber.
But still, the vacuum itself has no defined temperature.
shannon wagoner
On Wed, 30 Apr 1997 13:50:22 -0700 ( Ira Hsu <iy...@columbia.edu> )
wrote:
>Here's an [idle] thought:
> What would be the temperature inside a vacuum? Or would there be a
>temperature? I guess that inside a true vacuum, there would be no
true vacuum, absolute zero.
>moving particles; thus there could be no kinetic energy and no thermal
>energy. If you stuck a thermometer in the vacuum and and put the vacuum
>in a microwave, would you get a temperature reading? Since microwaves
>can pass through a vacuum... right?
>
DaveHatunen
In article <3376058d...@news.campus.mci.net>,
shannon wagoner <sha...@som-uky.campus.mci.net> wrote:
>On Wed, 30 Apr 1997 13:50:22 -0700 ( Ira Hsu <iy...@columbia.edu> )
>wrote:
>
>>Here's an [idle] thought:
>> What would be the temperature inside a vacuum? Or would there be a
>>temperature? I guess that inside a true vacuum, there would be no
>
>true vacuum, absolute zero.
No. Temperature is a quality of matter. A true vacuum has no matter and
no temperature. Not zero degrees temperature, but *no* temperature.