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Let's say that there is a galaxy on the edge of the observable universe. Let's say also that in the near future we create a specific camera feature that turns everything we see on screen to a mirror. The question: Can we use Stars of that Galaxy to see past the observable universe?

Mohamed Safi
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    How would the magic mirror feature help? – Jeff Apr 26 '16 at 19:41
  • if the mirrors of those Stars are angled in such a way , to see other reflections of other galaxies past the observable universe – Mohamed Safi Apr 26 '16 at 19:45
  • this question is somewhere between unclear and ill-posed – anon01 Apr 26 '16 at 22:26
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    If the light could reach the distant stars, bounce off of them and come to us... why couldn't it just come straight to us without a mirror? – Asher Apr 27 '16 at 03:03
  • @Asher How would the light bounce of them though without a mirror or a reflective substance ? – Mohamed Safi Apr 27 '16 at 09:03
  • The point @Asher is making is that the light wouldn't need to bounce off a mirror. If enough time has passed for us to be able to see something reflected in a mirror, then enough time has passed for us to see it directly. No need for a mirror. – NeutronStar Apr 27 '16 at 15:43

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The observable universe is defined by how far light has been able to travel since the Universe began.

If a distant star were to be turned into a mirror, we would only be able to see that portion of the universe that has had time for its light to reach the star, reflect off the mirror, then travel to us. Take an imaginary star right on the edge of the observable universe (I say imaginary because stars didn't form until some time after the universe started, so there exists no stars at the edge of the observable universe). Light from this star, whether emitted from the star or reflected off the star as a mirror, will take the age of the universe to reach us. Since it will take even more time for the light that is reflecting off that mirror to reach the mirror from its original source, light from objects more distant than that star will not have had time to reach us. In fact, the reflected light from such objects will not be able to reach us any sooner than the light from the objects themselves, not reflected.

NeutronStar
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  • Looking at it from a different point of view, if we can see that star at the edge of the universe and the lights it reflects, can't we in principle figure out what the things that lie beyond it look like? (we're not waiting for new light to travel) – Mohamed Safi Apr 26 '16 at 20:06
  • But you are waiting for light to travel from you magic mirror. And there are no magic mirrors. – Jon Custer Apr 26 '16 at 20:17
  • @MohamedSafi, it takes time for light from the stars beyond the edge of the observable universe to reach the mirror in the first place, before it can be reflected. The star with the mirror, we are seeing how it looked like right as the universe began, and at that point light has had no time to travel anywhere, so the mirror on the star isn't reflecting anything yet. – NeutronStar Apr 26 '16 at 20:24