The Sun is the star at the centre of our solar system. The temperature and density of material at its core produces nuclear fusion which results in it radiating a significant amount of electromagnetic energy. The Earth orbits the Sun at an average distance of about 149.6 million kilometres (92.96 million miles) and therefore receives some small fraction of this radiation on its surface. However, the resulting incident solar radiation is the most important source of energy for most biological and meteorological processes here on Earth. Thus it is important to have some understanding of how the Sun produces radiation and how that radiation impacts the Earth.