Why does the mass of an object increase when its speed approaches that of light?
A charged particle that is accelerated through a particle accelerator like CERN undergoes this phenomenon: the particle gains more mass as it gets pushed to higher and higher speeds.
So Einstein's (most famous) equation is E=MC^2. If we're assuming the speed of light (or any EM wave) is constant, and the mass we put into this device is known at the time, the only thing that can change is energy input.
If more energy is put into the machine (with the effect of moving the particles within it at faster speeds), than the mass MUST increase right, since the speed of light is the absolute limit, a known quantity? The "C^2" part remains unchanged, and cannot be changed.
My question is, why is an increase in velocity of a particle the same as E, energy? So velocity is the same as energy is the same as mass? Is that right? We can consider all 3 of these things as equivalent: mass, energy, velocity?