ok here is my idea, imagine your traveling in a space craft, with an acurate clock, one on earth as well and they start at the same time.
in order to reach our nearest start which is 4 light years away u have to get thar* gasp*.
now as you go faster time slows down for you.
so if you go at 1/2 the speed of light for example time will slow down by half, therefore you would on board the spacecraft think you are traveling at light speed. (this is an imaginary example to prove a point)
so it will take 8 years to get there but you will only feel 4 years of travel.
time ( i think) slows down more as you speed up and approch the speed of light, (correct me if i'm wrong).
now as you speed up MOAR to for example 75% the speed of light, time is going just 25% speed, so if "feels" as if you are going 2 times light speed. it will take 6 years (reall time) to get there but only 2 years in the spacecraft.
now this is why u can't reach light speed, as you get nearer to light speed, not only will u need MOAR fuel, but you will accellerate slower, as the engine is going slower, for example at 50% light speed, time will be going 50% slower and therefore so will the engines so thats 50% slower accelleration, therefore as we approch light speed, 99.99% of the spped of light, the engine that was ridiculously overpowerd now pales in comparrision to a 1 millivolt battery in realtime, it still accellerates the craft but it gets exponentionally slower as it speeds up, not only that but time will contine to seem to be speeding up outside the fraft from your persective, to you it will seem that you are accellerating at the same pace, but in real time you are not getting much faster, therefore time onboard the spacecraft will start to allmost stand still as you reach nearly the spped of klight, which is impossible beacuse it is a supertask.
because of this it will seem to you that as you reach the speed of light that the universe is speeding up exponentionaly, and becore you know it a "googleplex" years in real time has passed in 1 second (look up a googleplex if youi need to) and the universe along with your craft is destroyed via heat death/ dimensional collapse or whatever.
i think the only reasion particles that travel faster that light can do so is because they may have negative mass (somehow
), and perhaps light is as a particle zero or almost zero mass, which would make light able to travel at almost the top speed making light speed almost the limit in which case light speed is possible but time travel is not.