Fusion:
* Repelling forces: Fusion involves combining light nuclei (like hydrogen isotopes) to form heavier ones. These nuclei are positively charged (protons), and therefore repel each other due to electrostatic forces.
* Overcoming the barrier: To overcome this electrostatic repulsion and bring the nuclei close enough for the strong nuclear force to bind them, they need to be moving extremely fast. This requires incredibly high temperatures (millions of degrees Celsius), providing the kinetic energy needed to overcome the repulsion.
* Quantum tunneling: At these high temperatures, some nuclei can also "tunnel" through the electrostatic barrier, even though they don't have enough energy to overcome it classically. This is a quantum mechanical effect.
Fission:
* Unstable nuclei: Fission involves splitting a heavy nucleus (like uranium) into lighter nuclei. These heavy nuclei are inherently unstable due to the strong nuclear force being weaker than the electrostatic repulsion between the protons.
* Triggering fission: A neutron striking a heavy nucleus can disrupt its stability, triggering fission.
* No high temperature requirement: While high temperatures can increase the probability of fission, they are not required for the reaction to occur. The instability of the heavy nucleus is the primary factor driving fission.
In summary: Fusion requires high temperatures to overcome the electrostatic repulsion between positively charged nuclei, while fission is driven by the inherent instability of heavy nuclei, making high temperatures not a necessity.
