Altemative gravity theories

The gravitational field can not only generate gravitational force but also repulsive force. Besides universal gravitation, there exists universal repulsion between objects. Universal repulsion is dark energy. Whether an object experiences gravitational or repulsive force is determined by the velocity difference in the same or opposite direction between the object and the gravitational field. The velocity of the gravitational field is the speed of light. Other objects can only be affected by the acceleration of the gravitational field when it passes through them. The gravitational field is a kind of wave. The universe was born in the Big Bang and will end in the Big Collision. Light travels more slowly in regions with stronger gravitational fields.