Ok i'm a physics layperson, who has a question about relativity which i was hopging someone could answer in a way that i could understand. Ie without using mathematics hopefully as i failed high school maths(well quit but heh). I did pass physics so i'm not completely unfamiliar with some of the basics but a maths free or maths lite answer to my query would be much appreciated. Ok so question is. I get that you can't accelerate faster then the speed of light from you inertial frame of reference. To do so requires an infiniate amount of energy to cause your infinite amount of mass to accelerate once you get too 99.999999% (etc) of light speed. I think i get inertial frames of reference as well. However. i'm thinking that i don't cause i don't see how this leads to not being able to travel faster then light. Ie (and i reliase i'm very very likely missing something very obvious here hence why i'm asking for some assistance) lets say you build a spaceship which is capable of travelling at .25% of light speed ie .25c Thats very quick, but well within the laws of physics. Now let say you leave earth accelerating to .25c you then dock at a space station which is orbiting a planet some distance away from earth. And the speed that that station moves at (including the speed of the star the planet and the stations various velocities, ie rotational) is .25c faster then the speed the earth moves at. IE you don't have to change speeds to dock at this station, (though you could say +- a few%). YOu are now at rest in your new inertial frame of reference? aren't you? You can leave the ship, walk around the space station, etc etc. Then you leave, and you accelerate again .25c upon leaving this station and then ytou arrive at another station and you do the same thing, rinse repeat say 5 times. Aren't you then travelling at 1.25c? Now you've never accelerated to 1.25c you've only ever accelerated to .25c but relative to earth you are now travelling at 1.25c. Aren't you? So yeah basically if someone could in (hopefully) non mathematical terms explain why this doesn't work to me, twould be much appreciated. I think it's a problem with my understanding of inertial reference frames... but if it's all relative as soon as you stop accelerating aren't you then in a new reference frame? Ie once the airplane stops accelerating you can move freely around the cabin. anyways any and all answers/replies much appreciated.