Primary sources of energy

So where does the energy we use actually come from?

Radiation

In stars, hydrogen atoms undergo fusion producing helium. A very small part of the mass of these atoms is converted into energy which emanates from the sun as radiation. This is one of the two basic energy sources.

Fissionable elements

The other primary energy source is also formed in stars, but in a different way. When a star substantially bigger than our sun runs out of fuel, its core collapses and the star explodes in a process called a supernova. During this process, very heavy elements can be formed that release energy when they are split. These are called fissionables, and they are the second primary energy source. One should realize that nuclear fission happens naturally in every fissile material. This is known as nuclear decay. Without this process we could not exist, since it is this process that is largely responsible for the fact that the earth's core is still liquid, which helps to keep us warm and generates a magnetic field that protects us from cosmic radiation. The heat flow from nuclear decay inside the earth is around 30 [tera][]watt. (30 000 000 000 000 Watt!)