What Is the Source of the Sun's Energy?

The sun gets its energy from the many nuclear reactions that occur within it. The sun is essentially a very large ball of gas-light energy in the sky, composed mostly of hydrogen and helium that are constantly reacting with one another. Over the years, various scientists have created theories on just how the sun gets its energy. It was not until the twentieth century that this problem was solved.

Gravitational Energy

In 1850, German physicist Hermann von Helmholtz theorized that the sun got its energy from gravity. Just like a falling object has kinetic energy before reaching the ground, so energy was thought to be created by the gravitational pull of atoms toward the center of the sun. According this theory, Helmholtz thought the age of the sun was around 20 million years old. Although this concept has been disregarded, the sun may have at least started out with its energy coming from gravity.

Nuclear Energy

Due to an understanding of the theory of relativity, among other advancements, it is thought that the sun is about 4.6 billion years old. This marked increase in age estimates resulted from an understanding of nuclear energy. The reactions taking place in the sun start with basically with four hydrogen atoms in the form of four protons and four electrons. After the reaction, a helium atom is formed containing two protons and two neutrons. However, the mass of the particles created is less than the mass of the particles before the reaction occurred. Therefore, the mass that was lost is turned into energy in the form of energy of motion and gamma rays, which are electromagnetic waves of energy.

Significance

Mass being converted into energy accounts for the fact that the sun has continued to shine for eons and is calculated to continue to exist for billions of years into the future.

Gravitational Energy revisited

As stated by scientists at City University of New York-Brooklyn, the sun may have started out as a cloud of hydrogen that began to fall into itself due to the gravitational pull of its own atoms. After this collapse, the gas was at high temperatures and thus turned to plasma. The hydrogen divided into protons and electrons ultimately starting the proton-proton cycle reaction. These particles moving at high speeds helped to create an environment in which nuclear reactions can occur since high speeds are needed for such reactions. After a period of time, the temperature became very high within the sun, and the force of the sun's outward gravitational pull inward equaled the force of the fast-moving particles in the interior. Through continued nuclear fusion reactions we get the continuous energy output of the sun.

Considerations

Although hydrogen is considered to be the most abundant element in the universe, it is theorized that the sun will run out of its supply in about five billion years.