Explain the relation between Astronomical Unit and light year

Question

What’s the relationship between astronoMicah unit and light years

Answer 1

Hi Erica from Dunseith, ND...hope you had a great weekend.

I just wanted to add a tiny bit to what Arturo offered, as simple reference which I used to explain the difference to some of my middle school students. Yes, Arturo is correct...but my I add...it trying to understand the difference between an astronomical unit and a light year.

Think of it this way...(here is the definition scientists/educators will give: an Astronomical Unit is a scalar quantity, a specific value, the mean or average distance from our Sun to the Earth. Our Earth isn't an exact perfect circle...there are points in its orbit around the Sun is slightly closer and slightly further...LIKE a couple MILLION miles...that is why we say Average)...so basically, its like if you want to go to Bismarck from Dunseith. It is a specific distance...we'll say 99 miles...but you probably know the exact distance.

Now a light year, though it implies distance, it is not scalar, but a ratio, a measure of a distance in relation to a specific amount of time. In this case it is the distance light, a proton travels in one year. Yes it measures distance, but the difference is, is that it is related to the quantity of time. So, in essence it is a measure of not only distance, but time.

Like our example before...from Dunseith to Bismarck. if everyone traveled that route at a certain constant speed...it is distance related to time. Whereas if you only stay from Dunseith to Bismarck is 99 miles.

Hope this helps...I know Arturo made it perhaps easier, but I know this helped my students understand it better. Again...he is correct as well.

Have a great week at school

Answer 2

They are totally different distances.  An Astronomical Unit (AU) is the mean distance between the sun and the earth.  A light year (LY) is the distance that light travels in a year.