light year

[ehsanshekari]

what does "light" mean when we say "light year" ?
(I think it means "happy" am I right ?)

 

[BobK]

what does "light" mean when we say "light year" ?
(I think it means "happy" am I right ?)

:down: It means the distance traveled by light in a year. So it's an extent of space rather than an extent of time (although if you accept the view that spacetime is a single dimension, that sentence doesn't make a lot of sense - although trying to align theoretical physics with 'common sense' tends not to make much sense anyway;-))

Modern astronomers usually prefer to use the expression "parsec" ("parallax of one second of arc") - Parsec - Wikipedia, the free encyclopedia. As that article says,

Articles aimed at a wider audience, such as in newspapers and popular science magazines, often use a more intuitive unit, the light-year (ly).

b

 

[ehsanshekari]

I always thought I'm a clever boy , but your answer taught me that my IQ is under average .
(I understood the meaning of light year but I couldn't understand the other sentences.My English is too weak.)
Thanks
Ehsan Shekari