In 2014, NASA measured that the universe has a Euclidean shape. This discovery suggests that the curvature of space is merely a mathematical description of some more basic physical property of space. By extending the principle of equality of mass and energy to the space occupied by dark energy, a model of gravity was developed, where the gravitational force is due to the variable energy density of dark energy. The more curved the space, the lower the energy density of dark energy. A black hole, like any other stellar object, reduces the energy density of dark energy at its center in proportion to its mass and energy. In the centre of a black hole, the gravitational force is zero, as it is in all stellar objects. There are no wormholes in space, and there is no gravitational singularity at the center of a black hole. Gravity inside black holes follows Newton's physics.