Question

a light year is the distance light travels in one year. if the speed of light is about 3*10^5km/s, how long is light year in kilometers? (use 365 days for the length of a year)

Answer 1

Determine the number of seconds in a year of 365 days.

`\begin{gathered} 365\text{ days=365}*24*60*60\text{ sec} \\ =31536000\text{ sec} \end{gathered}`

Determine the light year in terms of kilometer.

`\begin{gathered} 1\text{ light year=3}*10^5*31536000\text{ km} \\ =94608000*10^5\text{ km} \\ =94608*10^8\text{ km} \end{gathered}`

So 1 light year is equal to 94608*10^8 km.