Dinosaurs extinction

I believe that dinosaurs extinction is closely connected to the gravitation pull of earth. The gravitational pull of earth should be much less during the dinosaurs time, compared to present time. Because of the less gravitational pull, the dinosaurs were able to grow much bigger. During this time, some thing caused the gravitational pull of the earth to increase, which could be due to collision with another celestial body or due to meteors shower. With that increased gravitational pull of earth, bigger dinosaurs were unable to move swiftly, that caused their demise. The smaller sized carnivores (such as raptors) died to lack of food over period of time. This lead to the growth of smaller sized mammals.