4th Dimension We happen to be at the perfect distance away from the sun for our mass, meaning that the earth just moves round in nice little circles. There is no proof that the earth isnt moving closer or further away from the sun, it could be 1 micrometer every year or something and we wouldnt notice. The last point is all to do with protons and electrons. If you look at a material's atomic structure (for arguements sake lets say Oxygen which is in group 6 and Hydrogen which is in group 1) you will see that the group it is in dictates the amount of outer shell electrons. Now, atoms like to be stable and have nice full outer shells so they will try to bond with other materials (in this case, to create water). So if you look at it group 1-3 atoms all have too many outershell electons (which are negatively charged) and group 5-7 all have too little. So quite obviously if you have too many outer shell electrons the atom is going to be negatively charged, if you have to little its going to to be positively charged and if you have 8 outer shell electrons then its going to be neutral. As you know + and - attract and thats how I understand it works (from GCSE Science). Wikipedia covalent and the other type of bonding you should have learnt about at GCSE