At another level the theories are radically different. In Newtonian physics Mass is an intrinsic property that does not vary. every particle has a set mass and that's it.
In Relativistic theory Mass varies with speed (they increase together). Hence you end up with ideas like rest mass (the mass something has if it is standing still). I believe that this is why only photons can travel at the speed of light (they have a zero rest mass) anything else ends up having infinite mass if accelerated to this speed, which takes infinite energy and is hence impossible.
These two concepts of mass are radically different from each other from a philosophical standpoint. That the maths of one can be derived from the maths of the other is somewhat deceptive.
This is a great breakthrough. This means that we can now wear full face tinfoil hats for even more protection without risking to bump into something anymore. Thanks that tinfoil hats are actually made of aluminum nowadays !
for an estimated 40 femtoseconds. Their is also the whole nearly invisible to extreme ultra violet radiation, which is not exactly in the visible spectrum.
Disclaimer: "These opinions are my own, though for a small fee they be yours too." -- Dave Haynie