In Chapter 6 you will learn more about variations in the Earth’s rotational orbit and its relationship to climate change.
All energy can be put into two major categories; kinetic and potential. Kinetic energy is the energy possessed by moving objects, such as electrical energy and motion energy. Potential energy is energy that is stored and poised to be used. Forms of potential energy include gravitational energy and nuclear energy.
Most of the energy that fuels the Earth’s processes comes from four primary sources: solar radiation, gravity, radioactive decay, and the rotation of the Earth. The heat from solar radiation drives many Earth surface processes such as evaporation, winds, and the climate system. Gravity makes rivers and other materials flow downhill and creates tides (from the Moon's gravitational pull). Radioactive decay creates heat in the Earth's interior magma (see Figure 1), while Earth's rotational forces influence currents of air and oceanic water.
Of these four primary sources of energy, much of the energy that fuels life on Earth originates from the sun’s solar power (i.e. solar radiation), which is a type of nuclear power called nuclear fusion. Read more about nuclear fusion in this document.
The sun is truly a glorious entity that has long been revered both scientifically and spiritually by humans for its incredibly powerful energy. The amount of energy produced by the sun in a two-week period is equal to the combined amount of all of the Earth’s stored energy, which is found in coal, oil, and natural gas reserves. In fact, one hour’s worth of the sun’s emitted energy exceeds what all 7 billion people on the planet consume in an entire year.
Coming up in the Energy and Spirituality section, you will learn how the sun has been a source of sacred power for many world religions.
Currently, fossil fuels such as coal, oil, and natural gas are the primary energy sources used by humans. These fuels were also originated by solar radiation, many millions of years ago: solar radiation made plants grow through photosynthesis, and it is the remnants of these plants, subject to extreme pressure and temperature, that became fossil fuels. Fossil fuels, with their very high energy density, were among the major drivers of the extensive development of human societies in the XIX and XX centuries. Unfortunately, the rate at which humans use fossil fuels is contributing greatly to changes in the climate that threaten the Earth and all of its inhabitants, including humans. Burning fossil fuels releases carbon dioxide, the major contributor to climate change. However, there are other alternatives based on solar radiation, such as wind or photovoltaic energy, that do not emit carbon dioxide. It is crucial that we continue to develop these and other technologies that can more efficiently capture solar radiation energy and distribute it to homes, buildings, and industry. Solar radiation power efficiently harnessed has the capacity to completely replace fossil fuels. We saw this in the El Hierro case study that opened this chapter. The challenge for the future is to build a world economy that is based on clean renewable energy.