<b>Gravity on earth</b><br /><br />As you are just about to jump, you are increasing the force between you in the ground, and they by decreasing the distance between the atoms of your feet and the atoms of the ground. Such distance become smaller than the distance when electromagnetic repulsion and gravity are at equilibrium. The result is an acceleration of your body upwards that is accompanied by a negligible degree of addition gravitational (i.e. accelerated reference frame caused) time dilation. Your angular momentum increases with respect to the earth increases (where your mass*velocity*radius with respect to the earth increases). As you leave the ground, the atoms at and below the surface of the ground begin to return to equilibrium and they regain their original angular momentum with respect to themselves. This must come from some where, which happens to be the lost of your angular momentum, and thus you fall down back to earth.<br /><br /><b>Gravity in the galactic disk</b><br /><br />To explain why galactic rotation curves are flat, all one has to understand that Newton gravity is just a special case of the conservation of angular momentum. To explain a more general theory of gravity, all we need to consider is the conservation of angular momentum. Consider stars of the same mass at some radius R from the galaxy's center of mass traveling at some velocity V. Let's say the R of each star changes. The first star increases its R by x, and the other star decreases its R by x. When the velocities do not change, the angular momentum is still conserved, which can be understood by observing the equation mvr+mvr=2mvr=mv(r+x)+mv(r-x).<br /><br /><b>Gravity in the solar system</b><br /><br />A solar system has fewer orbits than the galaxy and the levels are more discrete and tight than those found in the galaxy. Therefore conservation of angular momentum is largely (though not entirely) confined to individual orbiting particles. A constant angular momentum, mass*velo