Picture of galaxy idea...

Discussion in 'Astronomy, Exobiology, & Cosmology' started by LorencOfAlbania, Apr 13, 2005.

  1. LorencOfAlbania Registered Member

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    3
    Ok so a few days ago i had this thought about how every picture we have of a galaxy is wrong because of the time it takes light to get to earth. Now dont attack me cuz i know everyone knows the universe as we view it now is really as it was a long time ago because of the time it takes the light to reach us. My idea, or question really, was that since the galaxy itself is a few hundred thousand light years across, and one side of the galaxy is closer to earth then the other, wouldnt a picture of that galaxy show the galaxy as it was 200 million years ago on the side closest to the earth, and the other side of the galaxy would be shown as it was 200 million and 100 thousand years ago?

    BASICALLY... since it would take 100 000 years for the light at the far end of the galaxy to meet up with the light at the front of the galaxy and when the light reaches the earth together it gives the illusion of a whole galaxy from one time period when its really not.

    Anyways...any feedback? Am I wrong? Is this a widely known thing?
     
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  3. blobrana Registered Senior Member

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    Hum,
    well observed…

    However 100 000 years, to a distant galaxy, say a few <b>billion</b> light years away, is so small a length of time that nothing much would have happened…
     
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  5. LorencOfAlbania Registered Member

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    Yea thats what i thought cuz galaxies spin hella slow and stars come and go pretty slowly too for 100 000 years to make a difference. Its still a cool observation tho that i have never heard anyone talk about before.
     
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  7. Maddad Time is a Weighty Problem Registered Senior Member

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    You're correct Lorenc. We see the nearest edge of the galaxy as it was 25,000 years ago, and the furthest edge as it was 75,000 years ago. In the intervening 50,000 years the galaxy will have rotated one part in 5,000 (250 million years divided by 50 thousand years) of a full circle, or about 4 minutes of arc. It's not much, and indeed we cannot see the far side because it is obscured by dust, but many of the distant stars that we can see could be off by as much as two or even three arcminutes from where we see the nearby ones.
     

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