At the outset, it is important to understand that not all physical parameters are relativisatically variant. A number of parameters are invariant too. Charge is one of the examples. Rest mass is another example. The value of these parameters remains same in all frames of reference.
Certain formulae help in understanding relativity better. They are discussed as follows:-
E = ϒ m0c2 = m0c2 + K.E. (m0 is rest mass, E is total energy)
E2 = (m0c2)2 + p2c2 (p is momentum)
p = ϒ m0 v
m = ϒ m0
A cursory look at the above mentioned equations would suggest that mass and energy are not independent entities. The separates principles of conservation of mass and energy are essentially two dimensions of same principle of conservation of mass energy. The equations further reveal that mass can be created or destroyed by conversion of or to energy respectively.
The equations also suggest that a massless particle (a particle with rest mass zero) can occur provided its speed is equal to that of light. Such particle, though without rest mass, shall still display the properties of particle such as energy and momentum. This is also experimentally supported by the existence of photons.
A deep reflection on these issues opens a new dimension to the infinite universe before us. Does it not become clear that this universe of matter before us is a mere illusion?
With this, this discussion on Quantum Physics is closed. The motive towards discussing this is to understand this infinite universe of matter, space and time. It appears that Quantum Physics helps little in understanding that. It deals with matter, field, waves etc which exist IN space. So far, Physics has not questioned space as such. The issue of origin of space is not questioned. Such a major constituent of atom and therefore entire universe has been left as such by Physics. Some physicist do talk of quantization of space and time. It makes little sense to me as of now. The day one understands space as such, its origin and therefore the entity into which it dissolves, one will understand the universe in a much more practical sense.
As I have discussed in my post The Infinite Universe and Time and Space, it is essentially mind which creates both the concepts of space and time. This infinite universe, with its notions of space, time, motion, energy etc is nothing but a product of mind. Saying it a product appears wrong too. It is rather an apparent perception of a potential happening in an unchanged entity. To understand it theoretically is one thing, to realize it is quite another.