Temperature in Vacuum: Is it Zero or Undefined?

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Discussion Overview

The discussion revolves around the concept of temperature in a vacuum, questioning whether it is zero or undefined. Participants explore theoretical implications, definitions, and the role of electromagnetic radiation in determining temperature, with a focus on both conceptual and technical aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that temperature is defined by the vibration of particles, suggesting that in a vacuum, where there are no particles, temperature may be undefined.
  • Others argue that even in a vacuum, the electromagnetic field exists and can contribute to a form of temperature through thermal radiation.
  • A participant raises a hypothetical scenario about future technology that could block all electromagnetic waves, questioning whether temperature would still exist under such conditions.
  • One contribution references quantum field theory, stating that the vacuum represents an equilibrium state with a temperature of zero and all chemical potentials at zero.
  • Another participant mentions the concept of vacuum energy, suggesting it may be extremely small or possibly zero, and discusses the implications for temperature in a vacuum.
  • A later reply clarifies that while a vacuum may have a temperature close to zero, it can still have a measurable temperature due to residual radiation, such as the cosmic microwave background radiation at approximately 3 K.

Areas of Agreement / Disagreement

Participants express differing views on whether temperature in a vacuum is zero or undefined, and there is no consensus on the implications of blocking electromagnetic waves on temperature. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Limitations include varying definitions of temperature, dependence on the presence of radiation, and the complexities of quantum mechanics that are not fully resolved in the discussion.

ChloeYip
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I have learned that temperature is defined as the vibration of particles.
However, in vacuum, there is no particles.
In reality, no absolute vacuum can be done, so I can't find answer online.
Do you think the temperature (in Kelvin) is zero or undefined?
Thank you.
 
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Light
Heat glow.
Even in a vacuum there is the electromagnetic field. It is everywhere. It vibrates at different frequencies, some are visible light, some are warmth, some are too low-frequency and weak for us to feel with our senses.

Corresponding to any temperature there is a thermal mix of frequencies or mix of energies which you get as a heat glow off the walls of the box that you have your vacuum in. The light (in the general sense of electromagnetic radiation) inside the otherwise empty box has a temperature
 
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Thank you fo your answer.
What if technology get more advanced in the future and block all EM wave? Would there be still temperature?

p.s. I am just a high school student, can you please answer in a more simple way? Thanks.
 
The vacuum is the ground state of quantum field theory. For any quantum mechanical system the vacuum is the equilibrium state with temperature ##0## and all chemical potentials ##0##.
 
ChloeYip said:
Thank you fo your answer.
What if technology get more advanced in the future and block all EM wave? Would there be still temperature?

p.s. I am just a high school student, can you please answer in a more simple way? Thanks.
Are you familiar with the concepts of heat conduction, convection, and radiation?
 
"Observation indicates that in our universe the grand total vacuum energy is extremely small and quite possibly exactly zero. Many theorists suspect that the total vacuum energy is exactly zero."

http://www.scientificamerican.com/article/follow-up-what-is-the-zer/

ChloeYip said:
What if technology get more advanced in the future and block all EM wave? Would there be still temperature?

Probably not quite, but really really,really close...there would still be gravitational waves which are many,many times weaker [and which I think have never actually been detected they are so weak...really difficult to measure so far] ...
 
Last edited by a moderator:
ChloeYip said:
I have learned that temperature is defined as the vibration of particles.
It is not.
The precise definition of temperature is complicated. A vacuum still has a temperature, in the absence of an radiation the temperature is zero. Without matter but with a bit of radiation, like we have it in space far away from stars, the temperature is about 3 K, close to zero but not zero (and we can reach much lower temperatures on Earth).
 

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