Combustion, Fission, and Fusion Explained

Typically, when we refer to something "burning," we are discussing a process known as combustion. This is a chemical reaction where a fuel interacts with an oxidant, creating new compounds and releasing energy. When enough heat is applied, the weak bonds of the oxidant break, forming stronger bonds with the fuel, thus generating energy.

This process can become self-sustaining as long as all components—fuel, oxidant, and heat—are present. Remove any one of these, and the fire will extinguish.

Another method of energy release is fission, which happens when a large atom splits apart. A well-known example is the fission of uranium, which was pivotal in the development of atomic bombs. Large atoms like uranium and plutonium are unstable; when struck by a small particle, they break apart, releasing energy and potentially causing a chain reaction.

The third method is fusion. This is the process of merging smaller atoms to form a larger atom, which also releases energy. For example, when two hydrogen atoms combine, they create one helium atom. As the atoms combine into heavier elements, the process becomes increasingly difficult, but the energy released is significant.

In summary, we have three distinct methods of producing energy:

• Combustion: Energy release through breaking atomic bonds.
• Fission: Energy release from splitting heavy atoms.
• Fusion: Energy release from combining small atoms into a larger atom.

The Sun: A Fusion Reactor for Billions of Years

So, which of these processes explains the Sun's energy generation? The answer is fusion! The Sun began as a vast sphere of hydrogen, formed when the universe was still young. As gravity acted on this hydrogen, the atoms drew closer together, eventually fusing and releasing energy into space.

Fusion does not require oxygen; it merely needs enough energy to push the atoms together. The incredible heat and pressure at the Sun's core act as the catalyst for this ongoing fusion process.

While the Sun doesn’t depend on oxygen, it does need fuel—hydrogen. The Sun continuously converts approximately 600 million tons of hydrogen into helium every second, producing immense amounts of energy that warms the planets and sustains life on Earth.

What Happens When the Sun Exhausts Its Fuel?

Fortunately for us, fusion can also occur with elements other than hydrogen. As the Sun’s hydrogen supply diminishes, it will begin to fuse helium. This transition will cause the Sun to shrink while increasing its temperature, generating even more energy.

However, in about 4.8 billion years, the growing intensity of the Sun's energy output is likely to lead to catastrophic changes on Earth. As the Sun continues to convert hydrogen into helium, helium will accumulate at its core, producing even more energy as it compresses. Eventually, fusion will occur with heavier elements like carbon, while the outer layers of the Sun expand dramatically.

In the end, the outer shell will shed, leaving behind a dense core that has lost a significant portion of its mass. It’s a sobering thought that this process will ultimately lead to the Sun's destruction—but fortunately, that is billions of years away.

In conclusion, when we speak of the Sun “burning,” we refer to energy-releasing reactions that differ significantly from combustion on Earth. The Sun is a colossal fusion reactor, continuously fusing hydrogen into helium to produce energy. While we rely on combustion for our energy needs, the hope remains that one day we may harness fusion energy for our use.

How Does the Sun Burn in Space Without Oxygen?

To further explore this fascinating topic, check out the video below that discusses how the Sun burns in the vacuum of space.