Why do astronomers use light-years to measure distance in space?

Answer 1

Actually novangelis grazed it but didn't quite take it home. . . Astronomers DON'T use light years to measure distances. They use the parsec. Which is a parallax of one second of arc. The thing is that we seldom read scholarly works and scientific papers, what we get is the diluted versions that use the more accessible 'light year'. There are different units for different things, 'astronomical unit' is more comonly used for things within our solar system.

Answer 2

What would you rather they use? Yards or feet? That's like asking,"Why is the distance to grandma's house referred to as 3 1/2 hours. A: Because it is easier to understand how long it would take to get there traveling a certain average speed than to say," Grandma's house is 166,320,000 millimeters away." The distance light travels in a year is quite a long way and since distances in space are so vast, they have to use an astronomically huge distance as the unit of measure.

Answer 3

Why are you asking us? And, surely, 'Earth units' relates to any unit of measurement in comman usage on the planet Earth, and so would include light years. And astronomical units (approximately the mean distance between the Earth and the Sun). I am impressed with your grammar, though. You've even got your apostrophes in the right places. I mean, apart from the minor fact that you should end list items with a semi-colon, it's almost spot on. It's a shock to find a correctly spelt word around here.

Answer 4

Adding to Aleqkabo's answer:
imagine a straight line going away from you. Now imagine another straight line, overlaying the first - two lines starting from the same point, going exactly the same way.
Leaving the first one where it lay, imagine rotating the second line. The first end of both lines remaines the same; while the other end of the first line stay motionless, like a clock hand, the second line moves around the common point.
A circle is divided into 360 degrees. Each degree is divided into 60 minute divisions. An even smaller division of the circle, is the arc second, which is 1/60th of an arc minute, which is 1/60th of a degree, which is 1/360th of a circle. Imagine only rotating the second line one arc second from the first line.
Now, imagine beginning to walk between these two lines, from the origin where they meet and walking within the space between them. As you continue to walk, the distance between them increases, slowly, but uniformly.
When the distance between the two lines has grown to be the exact distance traveled by light in one year, then you are one parsec from the origin of the two lines.

Answer 5

Actually, astronomers use cgs units - which means we measure distances in centimeters. Frankly, light years would make a hell of a lot more sense.

Answer 6

In space the speed of light is little more than a snail's pace but 186,000 per second is a big number, the distance travelled in a year is truly impressive. Our sun is 8.5 light minutes from Earth.

Answer 7

To keep the numbers manageable. Try an internet search on "astronomical measure," "light year," "astronomical unit," and "parsec."

Have fun.

Answer 8

Actually, they don't use light-years, they use astronomical units (AU), which is the distance between the Earth and the sun. As this varies throughout the year, the current accepted value of 1 AU, regardless of the time of year, is 93 million miles.

Answer 9

Because distances are so vast it is a simple way for people who know very little about Space to get a general idea of how far something is.

Answer 10

Mainly because using miles or kilometers would result in huge numbers that are very difficult for the mind to grasp (all those zeros or "illions" get confusing).
Plus its helpful to have the distance to an object also tell us how long light takes to travel from it.