Lets see if I can muddy the waters a little further
Firstly, I think I should go back and discuss Relativity and Quantum Physics a bit more.
Relativity deals with the mechanics of objects that are moving at a significant fraction of the speed of light. If you are dealing with masses that
are moving very slowly, the maths is then the same as the Newtonian description.
Quantum mechanics cares about the very small, and how its behaviour is different from the normal scale of the Universe that we are used to.
If you talk about car/person sized objects then it is not relevent to think of QM effects as they are infinitessimally small.
This is similar to the way we don't worry about Special Relativity when dealing with objects that move at "every day" speeds, such as cars, trains, etc...
So it is possible to study the Quantum mechanics of a system involving a very small mass that is not moving close to the speed of light.
This would then be pure Quantum Mechanics and Relativity would not play any part.
It is then possible to extend QM to include the treatment of very small masses moving at close to the speed of light,
and you get Relativistic Quantum Mechanics.
So, firstly Slasher, while your maths may indeed be correct (I haven't checked it, we Particle Physicists are lazy and use a
system of coordinates in which c and h/2pi are both 1!) it does not apply to the car at speed of light question.
The car is very much a macro object and so any QM effects will be practically zero.
Relativity states that you would require an inifinite amount of energy to accelerate the car to the speed of light which is
why I say that the car will never reach the speed of light exactly.
Now, Look_Up:
There are three basic symmetries that apply in the interactions of
the fundamental particles:
C - Charge Conjugation
P - Parity Conjugation
T - Time Conjugation
If a process conserves one of these symmetries then it means that if you take an interaction, look at it, and then take the same interaction
after applying the symmetry you should get the same outcome.
As an example, C means changing the charge, in other words turning matter into anti matter. So if I have an interaction involving matter
particles it should behave exactly the same as an interaction involving the anti-matter particles.
The Parity symmetry involves flipping all 3 axes, that is X -> -X, Y -> -Y, Z -> -Z
So far I've mentioned interactions, without defining what I mean.
There are 3 fundamental forces that apply to subatomic particles (and then the fourth force is of course gravity).
The Electromagnetic force is what makes an electron repel another electron, it is also responsible for the forces that we experience everyday,
as well as for electromagnetic fields, light...
The Weak force results in nuclear decay, allows processes such as the fusion that goes on in the Sun and causes the decay of the muons that I refered to earlier.
The Strong force is what holds the quarks together into what we know as protons, neutrons, etc... It is the residual of this force that holds
the protons and neutrons together in the nucleus of an atom.
OK, so the point is that it was discovered that Weak interactions do not conserve P or C.
It is still believed that the combination CPT (that is change matter to antimatter, reverse all coordinates AND reverse the flow of time!) is
conserved in all interactions, which leads people to wonder if the combination CP is.
On first looking, it appeared that CP was conserved but on closer inspection it has been discovered that in the interactions of certain particles,
CP is violated at a VERY small level.
Now, why do we care about this?
The reason is that the Big Bang theory says that the Universe was produced in a "Bang" of energy, the Universe expanded, cooled and matter was produced.
The matter was produced through the production of matter/anti-matter pairs from the photons that constituted the original energy.
In the same way that if you take a proton and an anti-proton they will annhiliate and give you energy (ie photons), the reverse process is also possible (under certain circumstances).
So, the theory says that the energy was turned into matter/anti-matter in equal amounts.
But of course, we are in a matter universe, at least locally, so what happened to all the anti-matter?
A consequence of CP violation is that it results in matter behaving ever so slightly differently to anti-matter and so what we see as the Universe today is the tiny excess of matter that was left over after the matter and anti-matter in the early universe was formed, interacted and annihilated!
The goal now is to try to measure enough CP violation to explain the observed excess of matter over anti-matter in the early universe, and so far we come up WELL short.