What exactly is a light-year. Light-year simply explained!
A light-year, is a unit of distance often used in astronomy, to measure vast distances in space. It represents the distance that light travels, in a space entirely devoid of matter, otherwise known as a vacuum, in one year.
Since light moves at a speed of around 299,792 kilometres per second, the distance the light travels , in one single year, is 9.46 trillion kilometers.
Therefore, this vast distance is refered to as, one light-year.[delay: 1.3s]
Since even the speed of light has a limited speed, when we look at objects in space, we are actually observing them as they appeared in the past.
For example, if a star is located 10 light-years away from us, the light we see from that star today, actually started its journey 10 years ago. Thus, we are observing the star as it was 10 years ago.
Have a great day
Craig