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Is it possible for us to see our own galaxy from different perspective, as path of light emitted from our galaxy is curved by any possible ways and travelled back to our eyes even if it take much time?

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    $\begingroup$ The simple answer is no, we can't see ourselves. The universe is, as far as we can tell, flat, which means that everything we are looking at is, except for minor gravitational lensing, "in a straight line" from us. Since we can see all the way back to the cosmic microwave background, i.e. way before there were even galaxies, we are pretty much looking at a cross section of the (almost) entire history of the universe, it's just not our history but that of ever more distant places. $\endgroup$
    – CuriousOne
    Commented Feb 16, 2016 at 11:23
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    $\begingroup$ @CuriousOne Isn't it possible for light to take an U-turn around a black-hole? $\endgroup$ Commented Feb 16, 2016 at 11:31
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    $\begingroup$ No. Light doesn't behave like ray optics suggests and it can't be bent backwards like that. $\endgroup$
    – CuriousOne
    Commented Feb 16, 2016 at 11:34
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    $\begingroup$ @CuriousOne Can bending backward happen by means of collective gravitational lensing, one after the other? $\endgroup$ Commented Feb 16, 2016 at 11:44
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    $\begingroup$ @ACuriousMind By coherence I meant or wanted to say same as what CuriousOne said above. $\endgroup$ Commented Feb 16, 2016 at 11:51

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I think the answer is 'yes, in theory, but no in practice'.

First of all, bear in mind that a black hole can deflect light through an arbitrarily large angle: if you've seen the images of the black hole in Interstallar then it has these strange patterns around it which are because light can circle it many times before escaping. (Formally, this is pretty much an argument from continuity, although I think it was a surprising effect!)

So, in particular, a black hole can deflect light back the way it came.

So all you need is a quiescent black hole (no accretion disk or other stuff to confuse the issue) and some light from any source will be deflected back the way it came. Well, let's assume there is at least one such black hole 'visible' to us, then at least some light from the galaxy is going to be deflected back to it.

So in that sense, some light from the galaxy will clearly be visible to us having been deflected around such an object.

However:

  • this will be a ludicrously tiny amount of light;
  • I suspect strongly that there will be no useful image of the galaxy visible;
  • knowing where to look would be extremely hard, since the BH needs to be quiescent and there would therefore not be any interesting EM (or, now, gravitational) radiation reaching us from it to tell us where it is.

So: yes in theory but no in practice.

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Most of light emitted either reach other galaxies or escape to cosmological horizon. Our galaxies gravitational force is no enough to deflect it back.

Also, if it is deflected by some other black holes in a pattern, To get a complete veiw of galaxy we need light rays to simultaneously deflect back to us. Such possibility of a limited no. of such rays to to get to us is nill.

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    $\begingroup$ "escape to event horizon", "we need infinite no. of photons to simultaneously deflect back to us in coherence"..I'm afraid I have no idea what those phrases are supposed to mean. $\endgroup$
    – ACuriousMind
    Commented Feb 16, 2016 at 11:04
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    $\begingroup$ @ACuriousMind What do we say to brink of universe? $\endgroup$ Commented Feb 16, 2016 at 11:21
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    $\begingroup$ There is no "brink of universe" - for all we know, the universe is infinite and boundaryless. Are you talking about the horizon of the observable universe (that's called the particle or cosmological horizon, not the event horizon, which is the horizon of a black hole)? $\endgroup$
    – ACuriousMind
    Commented Feb 16, 2016 at 15:59
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I know the context is bending of space by heavy bodies, but that is lensing effect and we know lenses do not reflect, however small their focal length is.

Even if it was possible to reflect/turn back good amount of light somehow, it would be next to impossible to see a meaningful image.

When moon reflects sunlight, we see moon, not the sun!

We can see sun's image in water, so, it would be only possible if there was a mirror type of object in universe and happen to be positioned just right for us. Which we know is not there.

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    $\begingroup$ Its not about reflection, its about deflection by means of gravitational force. $\endgroup$ Commented Feb 17, 2016 at 6:28
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    $\begingroup$ I clarified that in my first line. $\endgroup$
    – kpv
    Commented Feb 17, 2016 at 8:16
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    $\begingroup$ But all optical lenses do reflect some light... $\endgroup$ Commented Feb 18, 2016 at 14:16

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