In this paper we resolve the grandfather paradox in non-quantum and quantum gravitation theories for time travelling in a time wormhole. For macroscopic bodies, the main solution is alignment of the thermodynamic time arrows, resulting in the time traveller destroying. For microscopic bodies and for small probability cases of macroscopic bodies, the main solution is fracture of the time wormhole. As a result, multi-world system appears. These explanations are similar in non-quantum and quantum gravity. On the contrary, we can clarify some problems of quantum gravity by this consideration. “Indestructible finite gravitation interaction of an observer with an observable system (resulting in the time arrows alignment)” and “instability with respect to even infinitesimally small interaction in the gravitation theory” can resolve the wave function reduction paradox of quantum mechanics.