Tun, te tum, please read these thoughts I've written and commment. Consider two hydrogen atoms. As they are electrically neutral they shouldn`t be any electro-magnetic attraction. But! They do do that co-valent boding thing which fills up their electron energy states. So isn`t there an attraction there? Consider a free electron and an atom. Despite the atom being electrically neutral, shouldn`t the free electron slightly prefer to move along one of the atom very high energy states? I mean, usually, for the sake of practicallity, we tend to ignore the fact that electron-in-atom states extend infinately into space because usually once they get past the first few, the nucleus has such little influence on the distant electron that it becomes negliable with respect to all the other quantum disturbances going on. Theorectically , with absolutly no disturbances, an electron could be in an energy state with such a radius as to make it's atom the size of the Earth, but in practice the electron always gets bumped off course. Never the less, theorectically this attraction still has a tiny effect on the electron. Now for the mega crux. Consider two hydrogen atoms. The electron in one atom is still sensitive to other atoms electron-energy states. We know this due to covalent bonding. Now even if the atoms are a large distance apart, this should still be true. The reason why you don`t get covalent bonding at higher energy state ( larger distances ) is because an atom is so much heavier than an electron. There's no way the electron in a high energy state with respect to one nucleus can drag a second, much closer, nucleus along it's high energy state path. Instead, usually the influence of this factor will only alter the paths of the atoms slightly from that of a straight line. However it would theorectically be possible to slow down the atoms so that high-energy-state convalent bonding could occur. The limiting factor comes in the form of the uncerntainty principle, which says that you can only go so far become background uncertainty energy will always knock any high-energy state covalent bonding atoms out of bonding. So in the real world we only see high-energy covalent bonding as having tiny effects on atoms. However, start summing the effects of however many atoms there are in a planet and the effects of high-energy state covalent bondings become considerable. This is gravity! Ahhh, there's nothing like pondering how gravity might arise from QM. It's my favorite physics thought. Recently I realized I'm not educated enough to know why this most intutive idea for gravity fails. So maybe someone could say why.