To understand why nothing can go faster than the speed of light, you have to have an idea of what energy is and what mass is. In barest essence, energy is a volume of stressed space, and it's usually travelling at c. You can start with a massless +1022keV photon and perform pair production to create an electron and a positron, both of which have mass. They also have spin angular momentum and magnetic dipole moment, and the Einstein-de Haas effect demonstrates that the angular momentum is "of the same nature as the angular momentum of rotating bodies as conceived in classical mechanics". There's something going round and round in there, the rotation is real. But it isn't a simple rotation like a planet, it's a two-component rotation where you "spin the spin axis", hence the Stern-Gerlach effect.
The mass is the result of a symmetry between momentum and inertia. A +1022keV photon has energy/momentum but no inertia. It's massless, and you can't make it travel at anything other than c. But after pair production where conservation of angular momentum applies, it's split into two 511keV photons, each of which is going round and round at c. One's the electron, the other one's the positron. They both have mass because the momentum is no longer moving laterally with respect to you, hence you see it as inertia, because it's like the photon isn't moving any more, because it's going nowhere fast. Because mass is a measure of the amount of energy that is not moving in aggregate with respect to the observer. It's something like the photon in a mirror box which increases the mass of that system, only the electron or positron is a system where a 511keV photon traps itself. Electron/positron annihilation unleashes the 511keV photons, and then there are no "boxes" left.
Of course, one of the problems of mass is that we use the word in many different ways. The accepted definition of mass is rest mass, which is the same thing as invariant mass, intrinsic mass, and proper mass. It's defined as the total energy of a system divided by c². There’s also active gravitational mass which tells you how much gravity the energy causes, and passive gravitational mass, which is a measure of how much an object is attracted by gravity. People also talk of inertial mass, which tells us how much force we need to apply to accelerate or decelerate an object. It doesn't apply for a photon because it travels at c, and you can't make it go faster or slower. Then there’s relativistic mass, which is just a measure of energy, which is why it applies to a photon. When you apply it to a cannonball travelling at 1000m/s, it’s a measure that combines the rest mass energy with the kinetic energy into total energy. It's important to note here that "rest mass" is better thought of as "rest energy", only for something like an electron the energy isn't actually at rest, because it's going round and round at c.
Kinetic energy is droll once you understand this. We use Compton scattering to move an electron, and in simple terms the electron is a photon going round in a circle like this ○. The Compton scattering effects an inverse Compton on the electron’s component photon, bending it like that U-shaped steel bar I mentioned in mass explained. But this photon is tied in a 511keV "knot". The deflection doesn’t break the knot. It stretches it like kicking a rubber ring, it alters the velocity vector and translates into motion. What you see is the same as what you’d see if you moved past the electron. It’s a photon travelling in a circular path, so if it’s side-on you'd see that circular path now looking like a helical path. One full turn round the helix represents the relativistic mass, the total energy. The circular component of this represents the rest mass. The difference represents the kinetic energy. It tells you how fast the energy that's going nowhere fast... is going somewhere!
It’s ridiculously simple, but that’s how it is. The kinetic energy tells you how fast the energy that’s going nowhere fast is going somewhere. Because accelerating an electron is like trying to stretch a spring. Ever seen a split-ring spring? It's like a un-joined circle, like this: Ω. To get the electron moving we have to deform the ring into one turn round that helix. The energy required increases as we attempt to deform it further. As we accelerate more and more, the helix is effectively stretched straighter and straighter. But we can’t stretch it straighter than straight. A photon travels at c, it can’t travel in a straight line at c and still be going round and round at c. It would have to go faster than light to do that. And light doesn’t go faster than light. So matter can’t travel as fast as light. No way no how, and it’s easy when you know how. Matter can't travel at c because it's essentially "made of light", and pair production and annihilation is the scientific evidence that proves it.
) inexperienced in particle physics. You claim that the energy of a photon is 'trapped' in the body of an electron/positron pair and that it is this spinning energy that causes mass - all well and good (and please correct me if my simplification of your theory is in error) - now here's my question.
