The remainder of the article will follow the convention of setting both α α = 1 and c = 1 , so units for X and x will be 1 unit = c 2 / α α = 1 . Be mindful that setting α α = 1 light-second/second is very different from setting α α = 1 light-year/year. Even if we pick units where c = 1 , the magnitude of the proper acceleration α α will depend on our choice of units: for example, if we use units of light-years for distance, ( X or x ) and years for time, ( T or t ), this would mean α α = 1 light year/year, equal to about 9.5 meters/second, while if we use units of light-seconds for distance, ( X or x ), and seconds for time, ( T or t ), this would mean α α = 1 light-second/second, or 299 792 458 meters/second).