The sun is one of the numerous stars in the sky. It is the closest star to the earth and lies at the center of the solar system. One rotation of the sun takes 27 days. It is 4.5 billion years old, which is thought to be its mid age. This means it shall keep shining for about five billion more years to come.

The surface of the sun is called photosphere. The temperature of the photosphere is 5,778 K. It is, however, much hotter at the core of the sun, being 15.7 million K. The energy is produced via a process known as nuclear fusion. This involves 2 hydrogen nuclei joining to form 1 helium nucleus, releasing energy.

The distance from the Earth to the sun is 149.6 million kilometers. The diameter of the sun is 1.392 million kilometers. It has an equatorial circumference of 4.379 million kilometers. These measurements represent 109 times the corresponding measurements of the earth. The sun has a surface area of 6.0877 trillion kilometer squared, about 11,990 times that of the earth. It has a volume 1.3 million times that of earth.

The heat from the sun reaches the earth through radiation. This energy is known as solar energy. Note that the planet absorbs only a small portion of this energy, the rest is reflected back to space. The absorbed heat is responsible for life on earth. It is also the source of the earth's climate, wind trends and water cycle.

Plants make their own food through photosynthesis, a process that is dependent on solar energy. Take note that all living organisms get their food directly or indirectly from plants. In addition, the sun is the cause of energy available in fossils. Examples of such energy sources are petroleum and coal.

Providing unlimited light and heat, the sun is the main source of energy to the earth. Extra applications of solar energy include lighting, generating electricity and in enhancing growth of plants in green houses. Considering all these factors, it is true to say that there can be no life on earth without the sun.