Why does fusion require extremely high temperatures?

Fusion requires extremely high temperatures to overcome the electrostatic repulsion between atomic nuclei.

Fusion is a process where two light atomic nuclei combine to form a heavier nucleus. This process releases a tremendous amount of energy, which is why it is the primary source of energy in stars, including our Sun. However, for fusion to occur, the conditions must be extreme, specifically in terms of temperature.

The reason for this lies in the nature of atomic nuclei. Nuclei are positively charged, and like charges repel each other due to the electrostatic force. This is known as electrostatic repulsion. In order for two nuclei to come close enough to fuse, they must overcome this repulsion. This is where temperature comes into play.

Temperature is a measure of the average kinetic energy of particles in a system. In other words, it's a measure of how much the particles are moving. The higher the temperature, the faster the particles move. When the temperature is high enough, the particles move so fast that they can overcome the electrostatic repulsion and collide with enough force to fuse. This is why fusion requires extremely high temperatures.

In the Sun, for example, the core temperature is estimated to be around 15 million degrees Celsius. At these temperatures, hydrogen nuclei (protons) have enough kinetic energy to overcome their mutual electrostatic repulsion and collide with enough force to fuse into helium, releasing energy in the process.

In attempts to achieve controlled fusion on Earth, even higher temperatures are required. This is because the density of the fuel in a fusion reactor is much lower than in the core of a star, so the fuel particles need to have even more kinetic energy to collide and fuse. This is why temperatures in fusion reactors need to be in the range of hundreds of millions of degrees Celsius.

In summary, fusion requires extremely high temperatures to provide the atomic nuclei with enough kinetic energy to overcome their mutual electrostatic repulsion and collide with enough force to fuse, thereby releasing energy.