I have a quick question, if an object is moving straight towards say Earth, isn't the gravitational field of Earth going to accelerate that object giving it extra energy? Where does that energy come from? Similar question, you have a hydrogen cloud in space, isn't the mass(energy) of that cloud less than the mass(energy) of that same cloud when it collapses into a star due to gravity? Again where does the extra energy come from? It may be a stupid question but I have to ask!