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Are we seeing duplicate copies of galaxies?

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posted on Mar, 24 2012 @ 08:05 AM
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Googled this question with no results, so I'll post it here to see if anyone can clear it up for me.

Let's say that 4 billion years ago a distant galaxy was in the position on the following image, and the light from this galaxy would take 4 billion years to reach where an X is marked:



After a million years or so, this galaxy has moved a good distance from its previous position. In its new position it will take 4 billion years for its light to reach the X.



While the light is traveling through space, the Earth has already formed and has become the planet we all know and love today.



Now, the question is, why wouldn't the light from that distant galaxy be shining down on us right now from both positions. Also, the light from that galaxy has been shining from every point along its path, so why aren't we seeing streaks of light?


edit on 3/24/2012 by jiggerj because: (no reason given)




posted on Mar, 24 2012 @ 08:11 AM
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a) in your model you state it took a million years for the galaxy to change positions. I would think that is why the light is not arriving at earth simultaneously. Unless I misunderstood the question

b) I would think it's because at that distance, the speed of the galaxy's movement is not sufficient to create the apperance of a streak to an observer here on earth


edit on 24-3-2012 by syrinx high priest because: (no reason given)



posted on Mar, 24 2012 @ 08:15 AM
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I think we wouldnt see streaks because we would only see it as it was at that particular point in time 4 million years ago



posted on Mar, 24 2012 @ 08:30 AM
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reply to post by jiggerj
 

When you look up at the Moon, should you see a streak?

No, because the light you see reflected from the Moon is light that is falling upon you at that moment, not the light that fell upon the spot on which you're standing minutes, or hours – or millions of years – ago.

Light reflected from the Moon earlier fell upon the spot earlier, when you weren't looking. And if you 'look' at the Moon with a long-exposure camera, you will see a streak.

The same goes for light emitted from a star or galaxy, however distant, as long as it is moving at less than the speed of light relative to us.

Galaxies moving faster than light do exist (due to metric expansion) but they lie beyond the edges of the visible universe and their light will never reach us.

So no, we aren't seeing duplicates of galaxies.

Good question, though. Flag and star.



posted on Mar, 24 2012 @ 08:31 AM
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delete
edit on 3/24/2012 by jiggerj because: (no reason given)



posted on Mar, 24 2012 @ 08:43 AM
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Think about light and time as pond ripples caused by events (stones) being thrown in, only instead of seeing one splash wave its more of a constant and never ending splash waves for the time the object emits EM radiation.

The photons that have taken their light speed life dodging other matter and particles through space to get to us, they are a tiny tiny pin point of the total wave that has been growing out from the galaxy origin for those 4 billion years.

The fact that ripples been going out for that long may indeed hide the fact the galaxy might be in a completely different place now, or exploded or perhaps combined with another galaxy. But now lets say that in one billion years after the waves we are seeing now arrive, new waves spanning out, carrying that new information that the galaxy has changed - We would still need to wait a billion years to see it, even though it might in fact not even exist at all and hasn't for 3 billion years. I dont know if that was a good enough explanation.

Short answer, no, we only would see current information. If it moved faster than the speed of light and could overtake its own light waves to change position, thats the only possible way to see a duplicate at the same time.



posted on Mar, 24 2012 @ 08:49 AM
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Originally posted by Astyanax
reply to post by jiggerj
 

No, because the light you see reflected from the Moon is light that is falling upon you at that moment, not the light that fell upon the spot on which you're standing minutes, or hours – or millions of years – ago.

Good question, though. Flag and star.


Thnx for the flag.

Don't ask me how, but I'm thinking that distance would somehow make a difference. Here's a far out scenario: Instead of photons coming at us from that galaxy, how about a huge meteor? A meteor is coming at earth from the galaxy's first position. A million years later, another meteor comes at us from the galaxy in its new position in the night sky. If we had the technology why couldn't we detect BOTH meteors coming at us? And, why would photons be any different?




posted on Mar, 24 2012 @ 09:31 AM
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reply to post by jiggerj
 


Instead of photons coming at us from that galaxy, how about a huge meteor? A meteor is coming at earth from the galaxy's first position. A million years later, another meteor comes at us from the galaxy in its new position in the night sky. If we had the technology why couldn't we detect BOTH meteors coming at us? And, why would photons be any different?

Photons always travel at the same speed, that's the big difference.

Your example doesn't really capture the situation. If you're comparing meteors and photons, then it's not detection but collision we should be talking about. And yes, two objects starting at different distances from Earth could both crash into it at the same time (this is what you are visualizing in the case of photons), but only if they were travelling at different speeds.

To be clear, it is the case of just one meteor that we should consider. It constantly emits or reflects photons, some of which collide with Earth. But these photons do not strike Earth at the same time. They arrive in a stream. When that stream is observed it shows an image of the meteor at the instant the photons left it, not any earlier or later image. Only if photons travelled at different speeds in vacuum could we see simultaneous images of the same object, all arriving in our telescope viewfinder at the same time! But changing velocity is something photons in vacuum never do.

Intelligently objected, though. As we see, the answer to your question brings to the table the whole business of relativity and the constant speed of light in vacuum. Another star for you; I hope we have both learned something today.



posted on Mar, 24 2012 @ 09:46 AM
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reply to post by jiggerj
 


When the galaxy has reached its new position, it's no longer "emitting" light from from its previous location. Therefore it's impossible to observe it in two different locations at the same time, unless it's moving faster than light - which it probably isn't. Just think of it like watching a recording of past events. You're just observing the galaxy as it was 4 billion years ago.

The asteroid analogy is flawed because there are two different objects that you're observing - two different asteroids, which are both reflecting light at the same time independent of the location of each other.



posted on Mar, 24 2012 @ 10:10 AM
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Originally posted by Astyanax
Intelligently objected, though. As we see, the answer to your question brings to the table the whole business of relativity and the constant speed of light in vacuum. Another star for you; I hope we have both learned something today.


Thanks. Of course, all I have to do is look up at the night sky to see how my premise is incorrect. Damn night sky! lol



posted on Mar, 26 2012 @ 05:59 AM
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Light is effected by electro-magnetism and gravity. So something on the far side of a black hole could show up on both sides of the object.
edit on 3/26/2012 by reitze because: cut the "possibly", it is effected by gravity.



posted on Mar, 29 2012 @ 01:00 AM
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Originally posted by reitze
Light is effected by electro-magnetism and gravity. So something on the far side of a black hole could show up on both sides of the object.
edit on 3/26/2012 by reitze because: cut the "possibly", it is effected by gravity.


Yep, this happens. And on some occasions we actually do see multiple copies of galaxies.

www.nasa.gov...




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