text: dont forces come only into existance only when a mass is applied into another mass? rather than a force being aplied to a single mass? i think the question you are asking is can something with no mass produce a force on an object. the answer is yes. a photon has no mass but it has energy. it's energy is equal to a constant times the frequency. this might seem a bit odd at first but if you have ever been into a science store they will probably have a light bulb with a vacume inside with a pinwheel going round and round. what is actually pushing the pinwheel is light because light it turns out will cause pressure on an object which we call radation pressure.   you are probably confused at this point since force = mass*acceleration, but mass is equal to energy -- remember e=mc^2, which we sometimes write as e=m by setting the speed of light equal to one. this means that you can actually create a massive particle from light -- this is called pair creation. it happens when a high energy photon becomes an electron and positron. also, when fission occur the opposite happens -- part of the mass becomes energy in the form of light.