What is the relationship between Matter and Energy?
Energy does not contain mass as such. The purest form of energy is light, photons. Those particles have zero mass, but since something that moves at the speed of light is supposed to have infinite mass, then the interesting product of 0 times infinity gives a value that is a function of the frequency of the photon. As such, a photon could be converted to a particle and its anti-particle (a process called pair creation), so it does convert energy into mass (of course, if the particle and its anti-particle are allowed to merge a few picosecond later, they will annihilate and convert their mass into energy, restoring a photon). As for what lies beyond the universe, where it expands into, not only we don't know, but there is no way of observing what could be beyond, as our observation capability will always be limited to our universe itself. But that the universe expands does not contradict the non creation of matter and energy. Space is just that: empty space. It is just like a number. You create a huge number, and call it a gadzillion. Do you have to have a gadzillion things being created just because you came up with the concept of the number? As for atoms to stop vibrating, as such, that is the absolute zero temperature. Theoretically, at that point, there is zero energy, hence matter would not exist either. But here is why this cannot occur. If you take away energy from an atom, you do so by lowering the energy level of its electrons, which emits a photon corresponding to the energy gab between the electron bands. Keep doing that until the electron is absorbed by the nucleus, and converts a proton to a neutron. Now you need to extract energy from the nucleus. How are you going to do that? How are you going to shield the resulting neutron from the influence of the rest of the universe, including radio waves, that penetrate everything?