# Is perfect thermal insulation possible?

Supposing someone says they have a sample of insulanium with the following properties:

• If you make a thermos out of insulanium, it will keep a drink hot or cold forever.

• If you put your hand on a sheet of insulanium, it won't feel hot or cold, because no heat is exchanged with your hand.

• A sheet of insulanium looks like a mirror at all frequencies, because it neither absorbs nor emits radiation.

Is such a material possible? Could you use the above properties of insulanium to design an experiment that would break the laws of physics?

• Such a material is not possible because it violates the third law of thermodynamics. See the humor section of en.wikiquote.org/wiki/Thermodynamics. :-) – CuriousOne Jul 21 '16 at 18:26
• @sammygerbil I think that it is not possible because it is not possible to manufacture a material that cannot release energy (in order for its bonds to form). – Owen Jul 24 '16 at 22:04
• @sammygerbil: I was thinking along the lines that such a material would have to have vanishing heat capacity, which, I believe, is only possible at T=0. I admit that I am not completely sure about the second part of the argument. – CuriousOne Jul 25 '16 at 20:23

I don't see how the existence of insulanium violates any of the laws of thermodynamics :

The 1st Law is a statement that energy is conserved. But there is no suggestion that energy is being created or destroyed here.

The 2nd Law states that the entropy of an isolated system only increases, never decreases. This is not saying that the entropy cannot stay the same for a very long time. When "forever" is reached, the insulanium will be at the same temperature as the contents of the flask - and/or its surroundings. The entropy will then have increased. The fact that it takes "forever" to reach thermal equilibrium is not a violation. Neither is it being claimed that the insulanium will get colder while the contents get hotter. That would violate the 2nd Law.

The 3rd Law states that any isothermal reversible process always increases entropy, except at absolute zero when $\Delta S=0$. No reversible process is being performed here. So I don't see how this Law applies.

The only thing I can find "wrong" with the description of insulanium is that its properties are not well defined. How long is "forever"? In physics - well, in engineering and technology! - unlike maths, we do not deal with infinities, and we have to be careful about zeros also. "Forever" could mean 10 years, which is far longer than any domestic thermos flask could keep something warm. It could mean 1000 years. That would be incredible, but it is not physically impossible.

Likewise, the tolerance for 100% reflectivity is undefined. Is this >95% or >99.5% or >99.995% or what? Even within a stated tolerance, "perfect" reflectivity at all wavelengths might be unrealistic but it is not physically impossible. We define a blackbody as an ideal absorber/emitter at all wavelengths. Although no real material with this property exists, it would not violate the laws of physics if it did.

Insulanium might have unrealistic properties. It might be highly unlikely that it could ever exist. But as far as I can see it does not violate any laws of physics.

I dont think it is possible to make anything 100% reflective although we can get arbitrarily close. The reason may be explained by tunneling by photons. Also,the entropy of an isolated piece of insulanium must increase with time. I think you can see now why such a thing is very very unlikely.

No, any material with a finite temperature will release thermal radiation, including mirrors, and it's not possible to make a mirror that's perfectly reflective.

Generally speaking, the best you can do is limit an object to only radiative heat exchange (i.e. no conductive or convective heating) which is why nice thermoses are vacuum-insulated.

No, it is not possible. Any material has black body emission which is a distribution of wavelengths across the electromagnetic spectrum. All materials have specific absorption frequencies at which they will absorb a photon. This will result in a transfer of energy from the hotter material to the colder one.

According to the three laws of thermodynamics, insulanium cannot make a drink hot or cold forever.

I guarantee you will feel the heat and that it will look almost like a mirror at almost all frequencies.

James Clerk Maxwell, the eminent Scottish physicist, came up with something called Maxwell's Demon (still being studied) that may debunk the second law of thermodynamics and make your proposition come true.

Some scientists have tried bombarding the electrons in matter with lasers to reduce their energy to very close to zero and create absolute zero (0 Kelvin) temperature but they have only been able to get very close to 0 K.