Temperature is a thermodynamic quantity that determines the degree of body heat. According to the second law of thermodynamics, spontaneous heat transfer is possible only from bodies with a higher temperature to bodies whose temperature is lower. In a state of thermal equilibrium, the temperature is equalized in all parts of an arbitrarily complex system. A change in the temperature of a body can be a change in some property that depends on it, for example, volume, electrical resistance, etc.

Temperature is a thermodynamic quantity that determines the degree of body heat

Most often, the temperature is measured when the volume changes. This is the basis for the construction of thermometers. The first thermometer was invented by Galileo around 1600. As a thermometric substance, that is, a body expanding with heating, it used water.

To measure temperature for practical purposes, thermometers are graded by melting or boiling points or some other way, so long as the process takes place at a constant temperature. The most common is the centigrade temperature scale (or the Celsius scale, named after the Swedish physicist who proposed it). On this scale, ice melts at 0 degrees Celsius, and water boils at 100 degrees Celsius, and the distance between them is divided into 100 parts, each of which is considered a degree. Since it is difficult to accurately reproduce the conditions for the melting of ice and the boiling of water, there are other reference points in the international practical temperature scale adopted in 1968 that can be more easily and accurately measured. As a result, the accuracy of temperature measurements in conventional laboratories is as high as a tenth of a percent, and in the standard laboratories, a thousandth.

In England and the USA, the Fahrenheit scale is sometimes used, in which the melting point of the ice is 32 degrees, and the boiling point of water is 212 degrees; in France - the scale of Reaumur: 0 degrees and 80 degrees, respectively. On the Kelvin scale, ice melts at a temperature of 273,15 K, that is, 0 degrees Celsius corresponds to 273,15 K.

The energy emitted by the body is proportional to the fourth power of its temperature. Thus, at 300 K from a square meter of the surface emits up to 450 watts. This explains, for example, the night cooling of the earth's surface below the temperature of the surrounding air.

The highest temperature created by man, 10 trillion K (which is comparable with the temperature Universe in the first seconds of her life) was achieved in 2010 when the lead ions collided accelerated to near-light speeds. The experiment was carried out at the Large Hadron Collider.