Everything pulls everything, apples pull planets, and planets pull apples. From this, Newton was able to relate the force of attraction between two objects to their masses and the distance between them. The picture of the world is more complicated. Einstein's general relativity predicts that accelerated masses should emit gravitational waves and they travel with the speed of light. Space - time is created by rotation of accelerated masses of stars. Accelerations are indistinguishable from gravitational fields. They are equivalent (The Principle of Equivalence). "Masses deform space, with the result that other masses follow curved tracks - as when the sun forces the planets to orbit around it" (Einstein, A., Relativity). The acceleration of Earth's space in the Earth's radius squared area forces any bodies to fall to the earth. The Earth's attraction force is determined by acceleration g. To solve a problem of movement we have to separate the notion of mass from the notion of weight and define when the mass acquires the weight.