question_answer 58)

                  The distance of a galaxy is of the order of \[{{10}^{25}}\,m\]. Calculate the order of magnitude of time taken by light to reach us from the galaxy.                

Answer:

                  \[t=\frac{\text{Distance}}{\text{speed}}=\frac{{{10}^{25}}m}{3\times {{10}_{8}}m{{s}^{-1}}}=3\times {{10}^{16}}s\]