Question

The distance of a galaxy from the earth is 5.6 $\times$ 10${}^{25}$ m. Assuming the speed of light to be 3 $\times$ 10${}^8$ m S${}^{-1}$ find the time taken by light to travel this distance.

Answer 1

Step 1, Given data

Distance of galaxy = 5.6 × 10²⁵ m
Speed of light = 3 × 10⁸ m/s

Step 2, Finding time taken

Time taken by light =$\frac{Distancetraveled}{Speed}$

Putting all the values

$Time=\frac{5.6\times {10}^{25}}{3\times {10}^8}=1.87\times {10}^{17}$ s
Hence time taken by light to travel is $1.87\times {10}^{17}$ seconds