Light Year

[ccyy1993]

What is a light year?

[SteveD]

The distance that light travels in one Earth year.

[Clanad]

At a speed of approximately 186,000 miles per second...

[Thunderchild]

light travels at 300'000 KMs a second (186'000 miles). a light year is equivalent to the distance tyhat light travels in one year 300'000 * 60 (seconds) * 60 (min) * 24 (hrs) * 365.26 (days) = the length of a light year. so if the closest star from us is 4 light years away (proximus centauri) then we see it as it was four years agobecause we see it as the light it emmits. this is valid for every celestial object for as light is the esence of all image we can actually see into the past because we see the most distant stars as they were thousand, millions, or billions of years ago !

[Gef]

Just under 6 miliion million miles.

[Clanad]

Actually, 669,600,000 miles...(1,080,000,000 KMs)

[bernardo]

Clanad - you seem to think that there are 3600 seconds in a year...

[Clanad]

Hmmm.... bernardo, obviously I relied on a calculator that was faulty (good as excuse as any).  How about 1.4093098 x 10 to the 14?

Thanks for the correction notice!

[Clanad]

So... Ok... once more...

5.8697136 � 10 to the 12th

Or roughly 6 trillion miles

[landie]

Further to your question regarding Light-years, I've an arrangement with Scottish Power to pay mine monthly.

[Gef]

Which is what I said!

[jake-the-peg]

Light years caught popular imagination and sound good in episodes of star trek.

The use of Parsec tends to be preferred in professional astronomy.

A parsec is the distance that a star has to be from the earth for it to appear to move by 1 second of arc over 6 months due to the earths orbit.

We know the earth's distance from the sun so we can work out this distance quite accurately (it's about 3.26 light years).

If you've used a method to determine a stellar distance based on the above - converting to light-years only adds another level of inaccuracy