<p>We can't, because the universe isn't curved enough to allow light to travel far enough since the big bang</p>
<p>If the universe was more highly curved, this might be possible. And the objects that appeared &quot;twice&quot; might not be very distant - or only one of the images would be distant.  It was even speculated that it might be possible to see the milky way and Andromeda as a distant pair of galaxies.</p>
<p>There were also searches of the cosmic microwave background to investigate if parts of it could be different views of the same pattern.  These turned up negative.</p>
<p>So while &quot;yes&quot; if the universe had sufficient positive curvature, it might be possible to see the same object twice, it turns out that the curvature of the universe is very close to zero, so we don't.</p>

CC BY-SA 4.0
2022-09-19T06:39:15.463Z
Could you add some references for the papers you mention? I'd like to have a look at them
Prallax
CC BY-SA 4.0
2022-09-19T07:20:43.437Z
The cosmic microwave pattern was a colloquium lecture I attended at university... long ago.
James K
CC BY-SA 4.0
2022-09-19T09:58:31.467Z
You say "the universe isn't curved enough", implying the universe has some curvature. But that's not true: the universe has *zero* curvature despite the intense desire of many astrophysicists to prove we live in some kind of bubble.
White Prime
CC BY-SA 4.0
2022-09-19T10:00:31.713Z
It might have zero curvature, its not known for sure is the curvature is zero, positive or negative....
James K
CC BY-SA 4.0
2022-09-21T17:17:52.930Z
Wishing I had someone nearby that knows this well enough to discuss some ideas I have on the subject of a "closed" flat universe.
Zenzizenzizenzic
CC BY-SA 4.0
2022-09-19T06:24:47.847Z
2022-09-19T06:24:47.847Z
James K
<p>Assuming the universe is curved and that is it possible to travel in a straight line and return to your starting point, it would make sense that at a younger age when the universe was smaller that light from an object sent in opposite directions would eventually reach the opposite &quot;pole&quot;.  Do we see any possibilities of this?  Seeing the same object from opposite sides in opposite sides of the sky?  Such object would have to be very old, I know.</p>

CC BY-SA 4.0
2022-09-16T15:02:11.100Z
The problem is that the early universe was opaque which essentially serves as a wall we can't see through.  So you could see the photons emitted in one direction, but not both.
Greg Miller
CC BY-SA 4.0
2022-09-16T20:15:18.327Z
Even if the curvature is positive the curvature is so small that light hasn't had time to circumnavigate the universe yet. I have some info about that [here](https://astronomy.stackexchange.com/a/31795/16685). And expansion makes that even worse. But people attempting to show that the curvature is positive *have* looked for such patterns.
PM 2Ring
CC BY-SA 4.0
2022-09-16T20:30:54.443Z
OTOH, we often see multiple images due to gravitational lensing. Eg, with the [Twin Quasar](https://en.wikipedia.org/wiki/Twin_Quasar), the first identified gravitationally lensed object, there's a 417 ± 3-day time lag between the two images.
PM 2Ring
<early-universe>
Can we observe the same very old object more than once?
Zenzizenzizenzic
# Can we observe the same very old object more than once?

(Asked by: username_0 on 2022-09-16)

Assuming the universe is curved and that is it possible to travel in a straight line and return to your starting point, it would make sense that at a younger age when the universe was smaller that light from an object sent in opposite directions would eventually reach the opposite "pole". Do we see any possibilities of this? Seeing the same object from opposite sides in opposite sides of the sky? Such object would have to be very old, I know.

**Tags:** early-universe
> **Comments:**
> **username_1**: The problem is that the early universe was opaque which essentially serves as a wall we can't see through.  So you could see the photons emitted in one direction, but not both.  
> **username_2**: Even if the curvature is positive the curvature is so small that light hasn't had time to circumnavigate the universe yet. I have some info about that [here](https://astronomy.stackexchange.com/a/31795/16685). And expansion makes that even worse. But people attempting to show that the curvature is positive *have* looked for such patterns.  
> **username_2**: OTOH, we often see multiple images due to gravitational lensing. Eg, with the [Twin Quasar](https://en.wikipedia.org/wiki/Twin_Quasar), the first identified gravitationally lensed object, there's a 417 ± 3-day time lag between the two images.  

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## 1 answers

### Answer by username_3 on 2022-09-19. Score: 6 | Accepted answer

We can't, because the universe isn't curved enough to allow light to travel far enough since the big bang

If the universe was more highly curved, this might be possible. And the objects that appeared "twice" might not be very distant - or only one of the images would be distant. It was even speculated that it might be possible to see the milky way and Andromeda as a distant pair of galaxies.

There were also searches of the cosmic microwave background to investigate if parts of it could be different views of the same pattern. These turned up negative.

So while "yes" if the universe had sufficient positive curvature, it might be possible to see the same object twice, it turns out that the curvature of the universe is very close to zero, so we don't.

> **Comments:**
> **username_4**: Could you add some references for the papers you mention? I'd like to have a look at them  
> **username_3**: The cosmic microwave pattern was a colloquium lecture I attended at university... long ago.  
> **username_5**: You say "the universe isn't curved enough", implying the universe has some curvature. But that's not true: the universe has *zero* curvature despite the intense desire of many astrophysicists to prove we live in some kind of bubble.  
> **username_3**: It might have zero curvature, its not known for sure is the curvature is zero, positive or negative....  
> **username_0**: Wishing I had someone nearby that knows this well enough to discuss some ideas I have on the subject of a "closed" flat universe.  

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