A light year is the total distance travelled by a beam of light in one year. A beam of light can travel at up to 300,000 km/sec and the approximate distance covered in a year works out to be 9,470,000,000,000 km (1 light year = 9.47 x1012 km).

So why did scientists create this new unit of measure?

Well as you can imagine the universe is so vast that talking about the distances between stars and planets was just unmanageable with miles and kilometers. For this reason a standardized unit of measure which we call the light year was created.

another reason to measure in lightyears is that we are reminded that what we are veiwing happened quite some time ago. what we see is not necessarily what is.

More appropriately, what we see is most definitely NOT what is. Many of the pictures we have are of things no longer in existence. Most notably, anything outside of our galaxy is doubtless in a different location/stage of development than what we see. After all, we're talking anywhere from tens of thousands to several billion light years.

Another unit of measure, though seemingly less common in use, is the parsec.

Hey, I saw star wars, and I'm going to go with the "Han Solo" definition. Sorry guys.

Han Solo: Han Solo. I'm captain of the Millennium Falcon. Chewie here tells me you're lookin' for passage to the Alderaan system?

Obi-Wan: Yes indeed, if it's a fast ship.

Han Solo: Fast ship? You've never heard of the Millennium Falcon?

Obi-Wan: Should I have?

Han Solo: It's the ship that made the Kessel Run in less than twelve parsecs. I've outrun Imperial starships. Not the local bulk cruisers mind you, I'm talking about the big Corellian ships now. She's fast enough for you old man. What's the cargo?

Family Guy style:

Chris(Luke): "Is it a fast ship?"

Peter(Han Solo): "Are you kidding, it's the ship that made the Kessel Run in less than 12 parsecs." Chris

(Luke): "Isn't a parsec is a unit of distance, not time."


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And yes, I'm aware of the 'minimal travelling path' rationalization for this quote - I just think its BS. I think its a creative 'explanation' for what amounts to poor editing.

Less than 12 parsecs? Sheesh that is nothing!

Mine the Millenium Stellar Warhawk goes under 9 parsecs!

I remember being annoyed hearing that when the movie first hit the box office.