The speed of light
In this article we read about what is a light year and how do we measure the distance of celestial objects.
In vacuum light travels at 299792458 meters per second. Wait ! That number is not even readable, to put it in a better perspective it is 299792 kilometres per second
So one can say light travels @ 2.99 lakh kilometres per second
(186k miles per second)
Now we multiply distance traveled by light for a minute and then into hours, days, months and finally for an entire year.The total distance traveled by the light in a year will be a number which you won’t bother to read.
Just know that its a very very huge number close to 9.5 trillion kilometres also called as One Light Year
Why do we need it
We cannot measure the distance between two stars in kilometres. That will be ridiculous.
The closest star to our Sun is Proxima Centauri which is 4.5 light years away. You got it right it will take 4.5 years to reach this star if we ever travel at the speed of light. In general, Light Year helps us to measure the distance in space at ease
Fun Fact: If this Proxima Centauri star explodes right now, it will take another 4.5 years for us to see it in action in our telescopes from earth! Because only then its light would have reached earth to witness the explosion.