What is nuclear fusion?

The process of atomic nuclei combination, or nuclear fusion, is a bit like a dance between two partners that become one. It involves two or more atomic nuclei coming so close together that they merge to form a new, heavier nucleus. Imagine two soap bubbles joining to become a single, bigger bubble.

Nuclear fusion happens under extreme conditions, with temperature and pressure so intense that atoms are stripped of their electrons, creating an environment of naked nuclei, known as a plasma. These nuclei are positively charged, and since like charges repel each other, it requires a considerable amount of energy to bring them close enough to combine. This is why such conditions are typically only found in the cores of stars—nature's own fusion reactors.

When nuclei fuse, they release some of the mass they contained as energy. This is what makes fusion a potential source of near-limitless power if we can learn to control it on Earth. Nuclear fusion is the same process that powers our sun and provides the warmth and light that sustain life on our planet.

The mass-energy equivalence is a revolutionary concept introduced by Albert Einstein, encapsulated by the famous equation \( E = mc^2 \)—where \( E \) is energy, \( m \) is mass, and \( c \) is the speed of light in a vacuum. This equation signifies a fundamental principle: mass can be turned into energy, and vice versa.

The speed of light, a staggering 299,792,458 meters per second, is squared in this equation, indicating that a tiny amount of mass can be converted into a massive amount of energy. In nuclear fusion, when atomic nuclei merge, a small portion of the mass is not part of the newly formed nucleus. This 'lost' mass is turned into energy, causing a release potentially far greater than chemical reactions like burning coal or natural gas.

When it comes to fusion's potential for power generation on Earth, this principle is what inspires the pursuit of fusion reactors. Such technologies aim to replicate the power at the heart of stars safely and cleanly - an energy solution that could last for millennia.

At the very heart of a star, including our own Sun, lies a process of incredible power: core fusion. This is the place where the magic of nuclear fusion naturally occurs. In these stellar crucibles, the gravitational force is so strong that it creates the necessary high temperatures and pressures for fusion to happen.

Imagine the core of a star like a crowded city center during rush hour, with atomic nuclei moving at incredible speeds, colliding, and sometimes sticking together to form new elements. This is the process that generates the energy of the star, eventually radiating out as the heat and light we can see from Earth. However, not every nuclear fusion reaction in stars is the same. They vary depending on the size and life stage of the star, with larger stars capable of fusing heavier elements in their cores.

Moreover, core fusion in stars is responsible for creating virtually all the elements on the periodic table, building them up from simpler elements like hydrogen and helium. This makes nuclear fusion not only the source of a star's power but also the creator of the basic building blocks that make up the world around us.