What I understood so far is that whole universe was born from a single point at which there was no time (or all the time was at single point - no present, no future) and then a big bang happened (may be), creating time, energy, mass etc. I want to learn physics at much deeper levels. So, I started with trying to know what is energy exactly. Right now I am at fundamentals. I am confused between light and heat energy. How is matter formed i.e, electrons and nucleus etc? How can we distinguish them with photons? Lots of questions to ask!!! But can some one answer the first question I have asked? Well the question is broad. But I am just looking for some comments or little ideas to start with. For Example: Potential energy of any atom is formed against the attraction i.e, Zero when the atom is not attracted by any other atom or at infinitesimal distance and is negative when it is bounded to other atom, positive when it is given some continuous force to overcome the attraction (or else positive p.e is unstable) And kinetic energy is formed by virtue of motion. Mass is property of and can be measured by energy of all the atoms combined together. Now I am struck with what is heat energy and light energy? I think thermal energy is nothing but the K.E. of atoms. And Light energy is when the atoms loose some energy or mass, it converts into light energy i.e, electrons drop to lower energy levels by loosing P.E. Or to say, light energy is energy of a wave that propagates the previous form of energy. And similarly the sound energy. At this point, I am confused of black body radiation concept. Every object absorbs and emits radiation continuously. So the radiations we are talking about is nothing but light energy right? So from this, I understood that Light energy is a wave for propagation of it's previous form or energy and heat energy is the kinetic energy of the atoms, right? And what is thermal energy? And somewhere I read that the maximum speed that a thermal energy can travel is the speed of sound. What does it mean? Is the thermal energy a wave or a kind of light energy or it is the other name for heat energy? Please understand my main intention. I am just trying to properly differentiate different forms of energies and the reason they are existed.