# What Is A Light Year

**Light is the fastest-moving stuff in our universe.**

**What is a light year**.
A perspective on how fast light travels is given followed by an introduction to the light-year which is a basic unit of astronomical distances.
Without light years discussing the distance between two stars would require the use of large unruly numbers.
It is the distance that light can travel in one year.

Light zips through interstellar space at 186000 miles 300000 kilometers per second and 588 trillion miles 946 trillion kilometers per year. One light-year is about 6 trillion miles 9 trillion km. Light Year is the distance that light can travel in one year.

Light moves at a velocity of about 300000 kilometers km each second. So this distance is 1 light-year. Specifically the International Astronomical Union defines a light-year as the distance light travels in 36525 days.

A light-year is the distance a beam of light travels in a single Earth year or 6 trillion miles 97 trillion kilometers. A light-year is a unit of distance. A light-year ly is the distance that light can travel in one year.

Our Milky Way Galaxy. Denoted by ly the value of one light-year is constant. For example the nearest star to us is about 43 light-years away.

A light-year is a measurement of distance and not time as the name might suggest. Distances in space are enormous - so big that our standard units of measurement kilometres and miles are just too small to be usefulSo scientists use some. So in one year it can travel about 10 trillion km.