question_answer

If the velocity of light is taken as the unit of velocity and one year as the unit of time, what must be the unit of length? What is it called?

Answer:

                  Unit of length \[=\] unit of velocity \[\times \] unit of time \[=3\times {{10}^{8}}m{{s}^{-1}}\times 1year\] \[=3\times {{10}^{8}}m{{s}^{-1}}\times 365\times 24\times 60\times 60s\] \[=9.45\times {{10}^{15}}m{{s}^{-1}}\] \[=1\,\text{light year}\]