Comparative Studies of Laws of Conservation of Energy, Momentum and Angular Momentum —No.2 of Comparative Physics Series Papers

As No.2 of comparative physics series papers, this paper discusses the same and different points of law of conservation of energy, law of conservation of momentum, and law of conservation of angular momentum in the traditional viewpoints. The same points: they belong to the three fundamental conservation laws in modern physics; and they are all widely used in physics. The different points: the law of conservation of energy is derived by the time translation-invariant, the law of conservation of momentum is derived by the space translation-invariant, and the law of conservation of angular momentum is derived by the space rotation-invariant; and in the fields of natural sciences, the law of conservation of energy is the most important and the most widely used law, while the other two laws are not so important and far-reaching. With the comparative method, the above traditional viewpoints are re-discussed. According to the principle of uniqueness of truth, the law of conservation of energy should be considered as the unique truth, and establish the science of conservation of energy; accordingly, within the whole physics range, the law of conservation of momentum and the law of conservation of angular momentum are not forever right, namely these two laws are correct only in some conditions (for instance, we can give the examples that these two laws are not correct as considering the actions of the friction and the like), therefore these two laws cannot be taken as the fundamental conservation laws in the field of physics; furthermore, in the case of no external force, the law of conservation of momentum may not be correct, and in the case of no external moment, the law of conservation of angular momentum may be not correct too. Finally, the improvements of the laws of conservation of momentum and angular momentum are discussed.