The Sun is the most important source of heat for our planet. However, its heat does not come from combustion reactions. Instead, it is produced in nuclear reactions. This is true to all stars, of which our Sun is one. The Sun's nuclear reactions are known as fusion reactions.

In fusion reactions, light hydrogen atoms join together, forming heavier helium atoms. At the same time, the reaction also produces energy. Fusion reactions transform chemical energy into heat energy. 


Fusion reactions take place in the Sun.

Humans can also make use of nuclear reactions. This is done in specially constructed nuclear power plants. These power plants produce large amounts of heat from small amounts of raw materials. This heat is then transformed into electricity. 

However, the nuclear reactions that take place in a nuclear power plant are actually the opposite of the Sun's fusion reactions. They are called fission reactions. In fission reactions, a chain reaction splits heavy uranium atoms into lighter barium and kryptom atoms. At the same time, the reaction releases heat energy. In fission reactions, chemical energy is transformed into heat energy. 


Fission reactions take place in nuclear power plants.

The raw material of fission reactions is uranium. Uranium is a metal that can be mined from the planet's bedrock.


Uranium is mined from the bedrock of planet Earth.