Temperature changes cause substances to change shape. But what is temperature anyway?
What is heat and what is cold?
Heat is created when atoms and molecules move. The faster the particles move, the more often they collide and transfer kinetic energy to each other. This makes a fabric warmer.
As the temperature rises, the state of substances changes, from solid to plasma.
The four temperature-dependent phases of substances are:
Fixed, the coldest condition. The atoms of, for example, metals and the molecules of, for example, ice are arranged in a lattice.
Liquid. In water, for example, the molecules are stuck together, but not for a long time.
Gas. The molecules of, for example, water vapor move completely free and collide more often than with a liquid.
Plasma. The atomic nuclei are separated from the electrons and move freely. Plasma is electrically charged because it consists of positive atomic nuclei and negative electrons.
What is the absolute zero point?
The lowest possible temperature is called the absolute zero point. At the absolute zero point, all atoms stand still and have no kinetic energy.
The atoms still have some quantum mechanical energy: the atomic nuclei and the electrons rotate within the atoms. Physicists therefore define absolute zero as the minimum energy state, where the atoms simply cannot cool any further.
The absolute zero point is -273.15 degrees Celsius, which equals zero Kelvin.
What is the difference between the temperature scales?
The Kelvin scale starts with absolute zero, and the degrees rise with the same interval as with the Celsius scale.
The Celsius scale is used in most of the world. It was developed in 1742 by the Swede Anders Celsius. Celsius based the dish on the melting and boiling point of water. Originally the boiling point of water was defined as 0 ° C, but in 1744 the scale was turned around and 0 ° C became the melting point and 100 ° C the boiling point of water. It made more sense to raise the scale as the temperature rises.
In the US the Fahrenheit scale is still used, which was developed by the German Daniel Gabriel Fahrenheit.
In the original version of the Fahrenheit scale, 0 ° F was the lowest temperature to which he could cool saline, and 100 ° F was the human body temperature. In the current scale, the freezing point of water is 32 ° F and the boiling point is 212 ° F.
How is the temperature of the earth measured?
The global temperature measurements started with measuring stations on land and on ships. In 1880 the coverage was sufficient to be able to determine the average temperature on earth every year.
Today there is a network of weather stations on all continents and on the oceans. The measuring stations are not evenly distributed throughout the world. For example, there are many more in Europe than in the Sahara.
For that reason, meteorologists divide the world into a grid with fields of five by five degrees. The average temperature measured by the local weather stations is calculated for each field. Then the average of all fields is calculated and the average world temperature is known.