Four laws of thermodynamics are unavoidable, despite all mystical hopes.

0th Law: When two systems are in thermodynamic equilibrium with a third one, they must be in equilibrium with each other. As Maxwell expressed it: “All heat is of the same kind”.

1st Law: Energy is conserved. The internal energy of a system changes as heat flows into it or out of it. In other terms: producing work without energy input is impossible.

2nd Law: The entropy of an isolated system never decreases. At equilibrium such system is at its maximal entropy. In other terms: the disorder of an isolated system can only grow. Or: the available energy (to be converted e.g. to produce work) of an isolated system is less than its internal energy. Or: the maximal efficiency of a heat engine is η = 1-TC/TH , where TC is the absolute temperature of the cold reservoir and TH of the hot one (in K). Or in vulgar terms: a lot of stones thrown into the air has no chance to fall back as a cathedral.

3rd Law: The entropy of a pure substance is nil at T= 0 K. In vulgar terms: maximal order is achieved when nothing goes on.

Sensible heat, heat content or latent heat: this quantity depends on the mass and on the specific heat capacity of the material. Heat involved in a change of its temperature is calculated as:

Where

- Q is the total heat implied in the change [J]

- m is the mass of the material [kg]

- C_P is the specific heat capacity at constant pressure [kJ kg^-1 K^-1]

Ice at 0 °C                   2.05

Water at 15 °C            4.186

Air at -50 to +40 °C     1.005

- T₁ and T₀ are the temperatures after and before the change [K]

Melting - Crystallisation, Evaporation – Condensation: heat is involved by the change of the physical state of the material.

For climate considerations, water is the vehicle of such processes:

Latent heat of fusion of water at 0 °C: 334 [ kJ kg^-1 ]
Latent heat of vaporisation of water at 100 °C and normal pressure: 2257 [ kJ kg^-1 ]
Latent heat of vaporisation of water at 14 °C and normal pressure: 2467 [ kJ kg^-1 ]

Planck’s Law

Planck’s law defines the radiance, the quantity of radiation that passes through or is emitted from a surface when in thermal equilibrium at a definite temperature.

At a given wavelength the radiance will be calculated as:

   [W m^-2 sr-1 Hz^-1 = W m^-2 sr^-1 s]

where:

- h is Planck’s constant [6.6260693×10⁻³⁴ W s²]

- c is the speed of light [2.99792458×10⁸ m s⁻¹]

- k is Boltzmann’s constant [1.380658×10⁻²³ J K⁻¹]

- λ/c [s^-1], where λ is the wave length [m].

Solving this over a range of wavelengths for a temperature of 5’776 K gives the following figure:

Radiance of a black body at 5776 K, the so-called effective temperature of the sun.

The wavelength at which there is a maximum is calculated by the Wien’s law:
In the case of the sun at 5776 K, λ_max = 0.002898/T = 0.502 µm; this is within the visible range of light (0.38-0.75 µm).

At the surface temperature of the Earth of 288 K (15 °C) the radiance spectra will be:

Radiance spectra at T =288 K

In this case the peak is at λ_max = 10.06 µm, in the non-visible infrared range.

Stefan Boltzman Law

This laws integrates Plank’s law and defines the electromagnetic power that is emitted by the surface of a lump of matter in relation with its temperature.

Where

- E is the flux of energy [W m^-2]

- ε is the emissivity of the black body (1 if perfect) [-]

- σ is the Stefan Boltzman constant 5.670·10^-8 [W· m^-2· K^-4]

- T is the temperature [K]

Thus at 5’776 K the sun emits 63.11 MW m^-2.

And the Earth, at its hypothetical 288 K and if a perfect black body,which it is not, emits 390 W m^-2.

Far away from us, at the temperature of the cosmic microwave background radiation of 2.7 K,
the radiation is a mere 3 µW·m^-2.

The emissivity factor of 1 applies only for a hypothetical perfect black body. Reality of matter is other:

Material	Emissivity
Aluminium (anodized)	0.77
Aluminium (polished)	0.039 - 0.057
Asphalt	0.93
Carbon (graphite)	0.98
Clay (baked)	0.91
Concrete	0.92
Cotton (fabric)	0.77
Glass	0.92
Glass (polished)	0.94
Gold (polished)	0.018 - 0.035
Grass	0.76 - 0.74
Human skin	0.98
Ice	0.97
Marble, white<	0.95
Sand	0.76
Silver (polished)	0.02 - 0.03
Snow	0.99
Stainless steel (polished)	0.075
Stainless steel 301	0.54 - 0.63
Teflon (coating)	0.38
Tile	0.97
Water	0.95 - 0.963
Wood (untreated)	0.90 - 0.95

Emissivity of various materials, Source: Wikipedia

Thus a thin aluminized sheet prevents heat loss of an injured person.