Heat transfer in nature is realized through the thermal conductivity, convection and radiation (lucaogou and radiation).

The mechanism of thermal conductivity is actually explained in the previous paragraph. Here is another example. When heated the end of a metal rod, its molecules begin to move faster, t. e. the internal energy at this end increases. Because on the other end of the rod molecules are moving slower, the inside of the rod with the help of chaotic motion of atoms and electrons there is a transfer of internal energy from the hot to the cold end. The transfer of internal energy from one part of the substance to other, due to the random motion of molecules and other particles of matter, is called the thermal conductivity.

 Among the different types of substances possess the best thermal conductivity metals. This is due to the, that they contain free electrons. It, that the thermal conductivity of the substance in the solid state more, than liquid, in liquid and more, than gaseous.

Consider the nature of convection. To show poor thermal conductivity of water, usually a container of water heated from above. While at the top the water may boil, and at the bottom will remain cold. However, if the vessel be heated from below, the water is heated evenly throughout the volume. The reason is, water when heated expands and its density decreases. If the heated water is at the bottom, the top, more dense layers of water under the action of gravity descend and displace warmer water up. This agitation of the water will occur until then, until all the water boils. Heat transfer, which takes place when mixing of non-uniformly heated layer of liquid or gas under gravity, called convection. It's simple to understand, in a spaceship in zero gravity convection no. (Think, why is the freezer in the refrigerator is strengthened at the top, instead of the bottom.)

It may seem, that convection cannot be attributed to heat transfer, as it relates to the work of gravity. However, with convection the increase of internal energy of liquid or gas occurs only at the expense of externally supplied heat, and the effect of gravity is reduced only to accelerate uniform heating of liquid or gas. Additional contribution to the internal energy of liquid or gas the action of gravity when convection does not. Therefore, convection refers to heat transfer.

The heat exchange between the Sun and the Earth is carried out by means of electromagnetic radiation. Electromagnetic radiation is created by the movement of electric charges and increases dramatically with increasing temperature. Radiation body, which is determined only by its temperature, is called thermal radiation.

The process of radiation occurs due to the internal energy of the body. When radiation is absorbed by some other body, the internal energy of a body is increased by energy of the absorbed radiation. Thus, by radiation, energy is transferred from hotter bodies to cooler substance. This type of heat transfer occurs in the absence of matter between bodies.