Question

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 1

Formula used: $\text{T}ime=\frac{\text{d}istance}{\text{s}peed}$
Given distance of a galaxy $\left(d\right)={10}^{25}m$
Speed of light $\left(c\right)=3\times {10}^{8}m/s$
Therefore, the time (t) taken by light to reach us from galaxy is-
$t=\frac{\text{d}istance}{\text{s}peed}=\frac{{10}^{25}}{3\times {10}^8}=\frac{1}{3}\times {10}^{17}$

$t=3.33\times {10}^{16}s$

Final Answer: $3.33\times {10}^{16}s$