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Summer.Haze

Light Years

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So I was jammin' in my apartment in the hoods of NYC, and I just thought to myself 'what does a light year really mean?'

 

I always actually wondered about this, and I'm trying to really understand it. I have no idea what people mean when they say things like 'you're actually looking into the past.' :huh: If I'm looking at a star for example, I'm looking at it now, not in the 'past.'

 

So if someone can explain the concept of light years in layman's terms, and help me reallyyy understand this, kudos to you. :thumbup:

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a light year is the distance light travels in a year. even though it has the word 'year' in it, it is a measure of distance, not of time.

the sun is 8 light minutes away. so the light we see in the sky from the sun is actually 8 minutes old, so you're looking 8 minutes into the past. if the sun shut off right now, we'd still see light for 8 minutes.

 

if a star is millions of light years away, it means the light you see is millions of year old, so you're looking millions of years in the past. you are not looking at the star as it is right now.

 

in fact you can't look at anything as it is 'right now' because it takes time for the light to reach your eye and for your brain to process it.

 

and r-z could totally already have answered this instead of making his comment about we non-scientific folks. <_<

 

Anyway I'm sure he'll find something wrong with my answer, then he'll correct it, then you'll get your real answer.

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Ahhh I think I kind of get it now. So the stars we see in the sky, are they presently non existent? We're just seeing the 'leftover' light? That 'leftover' light sure hangs around for a while, lol.

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Ahhh I think I kind of get it now. So the stars we see in the sky, are they presently non existent? We're just seeing the 'leftover' light? That 'leftover' light sure hangs around for a while, lol.

 

potentially. the star could already have died but we wouldn't know until millions of years later. or it could just be a really old star, so the light we see took millions of years to reach us but in the mean time the star still exists.

 

it's not leftover light. it's just light that came from really far away. if that star was 2 inches away from you there would be no 'leftover' light because the light from the star would reach you almost instantly.

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Also, just to add to the OP, why do we always call it the 'past'?

 

... what's wrong with 'the past'? that's just the word we use to indicate something that's already happened. :mellow:

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"...so you're looking millions of years in the past. "

Oh I see, I get the first part. But the 'past' thing, I'll understand it....eventuallyyyyyy. I keep relating it to time relative to earth. lol.

 

Thanks for the explanation oxy. :D

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"...so you're looking millions of years in the past. "

 

Oh I see, I get the first part. But the 'past' thing, I'll understand it....eventuallyyyyyy. I keep relating it to time relative to earth. lol.

 

Thanks for the explanation oxy. :D

 

Suppose you are recieving a letter from a friend far far away and it takes 2 years to reach you. When the letter reaches you and you read what the friend wrote to you, e.g., "I am well, I fell in love with a van today", you are percieving the status of the friend 2 years in the past. She might be actually dead by the time you read the letter.

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Suppose you are recieving a letter from a friend far far away and it takes 2 years to reach you. When the letter reaches you and you read what the friend wrote to you, e.g., "I am well, I fell in love with a van today", you are percieving the status of the friend 2 years in the past. She might be actually dead by the time you read the letter.

 

Ahhhh I seeeeee. Well, I'm glad I don't have friends in outer space.

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a light year is the distance light travels in a year. even though it has the word 'year' in it, it is a measure of distance, not of time.

the sun is 8 light minutes away. so the light we see in the sky from the sun is actually 8 minutes old, so you're looking 8 minutes into the past. if the sun shut off right now, we'd still see light for 8 minutes.

 

if a star is millions of light years away, it means the light you see is millions of year old, so you're looking millions of years in the past. you are not looking at the star as it is right now.

 

in fact you can't look at anything as it is 'right now' because it takes time for the light to reach your eye and for your brain to process it.

 

and r-z could totally already have answered this instead of making his comment about we non-scientific folks. <_<

 

Anyway I'm sure he'll find something wrong with my answer, then he'll correct it, then you'll get your real answer.

 

So if I'm star-gazing, the light that I see took a million years to reach me? Where has it been for those million years? What about the moon? Sometiimes it's really bright and sometimes it's not; so for example on the night of the full moon, when we say 'Oh wow the light tonight is so bright blah blah', in reality that light isn't really from the full moon? It's from an older moon? :blink: I'm confusing myself....

 

 

potentially. the star could already have died but we wouldn't know until millions of years later. or it could just be a really old star, so the light we see took millions of years to reach us but in the mean time the star still exists.

 

it's not leftover light. it's just light that came from really far away. if that star was 2 inches away from you there would be no 'leftover' light because the light from the star would reach you almost instantly.

But that would probably blind us, right?

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