How is lightyears the speed of light put into distance?

Answer 1

A light-year is the distance travelled by light in a year. It is simply used as a convenience, since the official SI unit - meters - results in very large numbers (for example, approximately 4 x 1016 meters to the nearest star).

Distances between planets in our Solar System are NOT usually measured in light-years, since a light-year is much more than those distances. Instead, the distances are expressed either in millions or billions of kilometers, or in astronomical units. One astronomical unit (AU) is the average distance from Earth to Sun (150 million kilometers).

Answer 2

It's really not so mysterious. Forget about light for a second ... just think about cars.

Imagine that every car in the world traveled at the same speed ... 5,280 feet per minute, let's say.

Never faster, never slower. Just a law of nature ... cars travel at 5,280 feet per minute.

Now let's say your grandmother lives 316,800 feet away from you. That's a big number, because

she lives so far away. In order to describe the distance to grandma's house, you want to invent a

bigger unit, so you don't have to say "three hundred sixteen thousand eight hundred feet" every time

you talk about the trip. You could invent a unit that's 5,280 feet long, and give it a name like "one mile".

Then the trip to visit her is easier to say ... it's still the same distance, but you only have to say "sixty miles".

Or you could make the numbers even more convenient. Invent a really big unit, to talk about

really long distances. How about the distance a car travels in one hour. That right there is

316,800 feet .. perfect ! Now, when you're planning a trip to visit grandma, you're talking about

a distance of . . . . . one car-hour ! That's a distance. It's the distance a car goes in one hour.

That explanation ran longer than I meant it to, but I think the details of the analogy are OK.

A "light-year" is a distance. It's the distance light travels in one year. It's a gigantic distance,

but you really need it in order to talk about the distances between stars.

The nearest star to us ... past the sun, that is ... is about 25,866,280,000,000 miles away.

I'm not even sure how to say that number, and even if I knew how, you'd be tired of listening

before I got to the end of it. So we don't use miles to talk about the distance to stars. We use

the distance light can travel in a year. That nearest star past the sun is ... 4.4 light years away.

Answer 3

Lightyears are not the speed of light. Lightyears are there to measure distance. One lightyear is the distance that light travels in one year.