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Why is 100% efficient thermal insulator impossible?

  1. Jan 4, 2007 #1
    Somebody told me this and I have yet to figure out even if the statement is true or not.
  2. jcsd
  3. Jan 4, 2007 #2


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    Because if it could be done, you could stop entropy. Which you can't.

    Even if you could stop conduction of heat, how would you stop a body from radiating heat?
  4. Jan 4, 2007 #3
    If u can stop entropy its lik saying u cud stop time.SO i guess its not possible
  5. Jan 5, 2007 #4


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    Translation: If you can stop entropy it's like saying you could stop time, so I guess it's not possible.
  6. Jan 5, 2007 #5


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    Stop entropy? What does that mean?
    If the question was, is there such a thing as a perfect insulator (i.e., has zero thermal conductivity), then the answer is "yes, a vacuum". Of course, you can't make a true vacuum, nor does a vacuum prevent radiation.
  7. Jan 5, 2007 #6


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    I like to look at such questions backwards: how could you make a perfect insulator? There are 3 types of heat transfer: conduction, convection, and radiation...

    As Gokul said, a vacuum will stop conduction and convection completely, but we can't make a perfect vacuum and even if you could, you'd have to support the structure with something. So you can't completely eliminate either conduction or convection in a device (though you can eliminate conduction between objects that aren't touching. But you can get either well above 99%.

    Stopping radiation is much more difficult than stopping either conduction or convection because it requires a perfect mirror that is perfect at all frequencies of radiation. And though you can get mirrors at in exess of 99% reflectance, the frequency range is limited.
  8. Jan 6, 2007 #7


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    Since a vacuum doesn't prevent radiation, how does that make it a perfect insulator?
  9. Jan 6, 2007 #8


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    It doesn't because it does not prevent readiation as gokul said.

    But this perfect vacuum must exist a place farther away than light has reached since bing bang? Because if no radiation or mass have reached the point, nothing can be there.
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