Is matter really convertible into energy and if so then how?

Answer 1

The usual example of the conversion of matter to energy is a nuclear explosion, or the nuclear fusion that takes place in the sun and is the source of the sun's energy. When hydrogen nuclei fuse into helium nuclei, there is a certain amount of mass that is lost; the weight of the helium nuclei is less than that of the hydrogen nuclei (or protons) which produced them. This extra weight is not stored in the form of particles, but in the form of (invisible) binding energy. It exists because there is no binding energy in a hydrogen nucleus, which consists of only one particle, whereas the helium nucleus with two protons and two neutrons has binding energy between all four of those particles (as a result of the strong nuclear force). This can be compared to the energy which results from a falling object. Height is a form of stored gravitational energy, and falling releases that energy. Similarly, when nucleons bind together, that releases potential energy. The quantity of energy is large enough to be easily measured in terms of mass. In reality, all energy is equivalent to some quantity of mass, so an object held high above the ground, which has gravitational potential energy, weighs slightly more than the same object after it falls to the ground and has given up its gravitational potential energy, however, that difference in weight is too small to detect. But all energy has mass, in accordance with Einstein's famous equation for mass-energy equivalence.