Why is 100% efficient thermal insulator impossible?

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Somebody told me this and I have yet to figure out even if the statement is true or not.
 

DaveC426913

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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?
 
If u can stop entropy its lik saying u cud stop time.SO i guess its not possible
 

DaveC426913

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If u can stop entropy its lik saying u cud stop time.SO i guess its not possible
Translation: If you can stop entropy it's like saying you could stop time, so I guess it's not possible.
 

Gokul43201

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Stop entropy? What does that mean?
Why is 100% efficient thermal insulator impossible?

Somebody told me this and I have yet to figure out even if the statement is true or not.
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.
 

russ_watters

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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.
 

DaveC426913

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then the answer is "yes, a vacuum". Of course, you can't make a true vacuum, nor does a vacuum prevent radiation.
Since a vacuum doesn't prevent radiation, how does that make it a perfect insulator?
 

disregardthat

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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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