The statement "energy can't be created or destroyed" is a fundamental principle known as the law of conservation of energy, which is a cornerstone of physics. According to this law, the total energy in a closed system remains constant over time.
When we say matter is being converted into energy, it is not implying that energy is created or destroyed. Instead, it means that matter undergoes a transformation where its potential energy (stored energy within matter) is released or converted into different forms of energy, such as thermal energy, kinetic energy, electromagnetic energy, or nuclear energy.
Two well-known examples of matter being converted into energy are:
Nuclear reactions: In nuclear processes like nuclear fission or fusion, the nucleus of an atom is altered, releasing a tremendous amount of energy. This energy is a result of the conversion of a small amount of mass into energy, as described by Einstein's famous equation E=mc², where E represents energy, m represents mass, and c is the speed of light.
Matter-antimatter annihilation: When particles of matter collide with their corresponding antiparticles (particles with opposite charges), they can annihilate each other, resulting in the complete conversion of their mass into energy.
In both cases, the principle of conservation of energy is upheld because the total energy before and after the conversion remains the same. Energy is merely transformed from one form to another, while the total amount remains constant.