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Author Topic: What is the temperature inside an air evacuated vessel?  (Read 2510 times)

Offline thedoc

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Greg Lorenz  asked the Naked Scientists:
   
Chris,
 
What is the temperature inside an air evacuated vessel?

Thanks,

Greg Lorenz

What do you think?
« Last Edit: 29/04/2012 12:35:01 by _system »


 

Offline syhprum

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Re: What is the temperature inside an air evacuated vessel?
« Reply #1 on: 29/04/2012 13:23:50 »
By definition temperature is a measure of the kinetic energy of the particles of a substance hence no particles no temperature.
 

Offline CliffordK

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Re: What is the temperature inside an air evacuated vessel?
« Reply #2 on: 29/04/2012 13:56:30 »
Of course, even space isn't a perfect vacuum.

Unless you could somehow exclude all IR, any device hung into such a vessel would tend to the temperature of the vessel.
 

Offline yor_on

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Re: What is the temperature inside an air evacuated vessel?
« Reply #3 on: 29/04/2012 16:10:33 »
Clifford, I think I see how you mean, but I assume that you expect there to be some particles for the infra red radiation to interact with? In a perfect vacuum it doesn't matter (a pun :) what the radiation gives for 'temperature' to us on Earth. It will still need something to interact with. It's the 'vibrational modes' of particles that change when IR interacts as I understands it, and without any particles we can't even prove a radiation. Only as it interacts.
 

Offline Bored chemist

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Re: What is the temperature inside an air evacuated vessel?
« Reply #4 on: 29/04/2012 16:20:49 »
Imagine that you have a thermometer in the middle of the evacuated chamber.
Both the thermometer and the walls of the chamber will emit (more or less) black-body radiation.
If the thermometer is hotter than the container then it will emit lots of radiation and thus it will cool down and the container will warm up. In the same sort of way, if the thermometer is initially cooler then the chamber then the chamber will cool and the thermometer will warm up.
In the end the thermometer and the vessel will have the same temperature.
So, it looks like the temperature, in the middle of the vessel, as measured by the thermometer is the same as that of the vessel.
 

The Naked Scientists Forum

Re: What is the temperature inside an air evacuated vessel?
« Reply #4 on: 29/04/2012 16:20:49 »

 

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