Why can't a particle accelerate to light speed in its own frame?

[Shark 774]

Hey, I understand why if you watch someone they can never accelerate to the speed of light: their mass approaches infinity so the necessary impulse reaches infinity. But what about in the frame of reference of the person approaching the speed of light. They notice nothing unusual about their mass/time/length so clearly the previous explanation doesn't fit. Maybe my first explanation isn't the best way to explain it? Need some help please!

Cheers -

 

[HallsofIvy]

?? In "the frame of reference of the person approaching the speed of light", nothing changes because their speed in that frame of reference is 0. The speed of any person or object in is own frame of reference is 0- nowhere near the speed of light!

You can only "approach the speed of light" (or be moving at all) in the frame of reference of some other person.

 

[Shark 774]

?? In "the frame of reference of the approaching the speed of light", nothing changes because their speed in that frame of reference is 0!

You can only "approach the speed of light" (or be moving at all) in the frame of reference of some other person.

Ah ok, so my question was a totally moot point! Thanks for that.

 

[Naty1]

But your question does point out an important aspect of special relativity: everybody's frame of reference is in general different and that is something that was not clearly understood before Einstein. Not only do different observers see different speeds, but time passes at different rates for each and each may measure different lengths as well...

The underlying principle is that it is NOT space and time that are fixed as we all might think from everyday [low speed] observations, these in fact vary with observer speed, but it is the speed of light that IS fixed, that is, the same for all observers.