Not gravitational lensing...but...

[EvilEye]

Is there such a thing as mirroring on a universal scale?

What I mean is... imagine looking into space with your telescope, and you end up seeing light that appears to be coming from the direction that you are looking, but somehow, it is actually just as far away and BEHIND you?

Let's say I look into the sky, and I see a light that appears to be 20 light years away, but in reality, it IS 20 light years away, but in the wrong direction, reflected back at me by some cosmic mirror effect, and the light is now 3 times as old (for me) as it would have been had I looked the other way... but now it is 60 years too late to locate it.

[Peter Wilson]

You mean like a Quark Mirror?

[EvilEye]

You mean like a Quark Mirror?

I tried to click your link.. but it doesn't appear to be a link...

I'll go look it up.

(edit) Ok... I looked it up

I don't get all the physics of it as a baby ... but I did see the number 3 alot.

[mugaliens]

Here's a better link: Quark mirror

Only $285, huh? I think I'll pass...

Back to the actual question, it's unlikely, for when such "mirrors" between us and distant galaxies moved, they'd cause all kinds of funny optic effects that we'd notice, including galaxies and stars moving rapidly or winking in and out of existance, half-galaxies, serious warps, etc.

Since we don't see that, we conclude that the fabric of space-time is fairly flat, interrupted only by the occasional star.

It's also fairly empty, with about 5 atoms per cubic meter, at least in the observable universe.

[EvilEye]

That wasn't link I found.. mine had real physics in it, but really had nothing to do with my thought.

Thank you mugaliens... but I'm not so sure we would notice it fast enough.

If the light coming at us for 20 light years gives us information we believe to be true, and and then moves a little... the only thing we MIGHT notice... is that it is moving in the wrong direction... no? (Like trying to comb the back of your own hair in 2 mirrors and your hand goes the "wrong" way)

[mugaliens]

For distant objects, it's really not feasible to compare photographic plates over 20 years to detect relative motion. For nearby ones, however, it's easy, and the relative motions match predictions for a relatively flat space. We largely extrapolate this for more distant objects and compare what we can, such as red-shifting.

[EvilEye]

well... that's pretty much exactly what I'm saying.

At a relatively close distance it is easy and we use that to judge large distances. But could we be fooled if we think we are looking one way when really what we are seeing is somewhere else?

Hopefully this isn't ATM.. because it is only a question.

I've heard many physicists say that in every direction is the universe...

..and that If I left in a straight line and traveled far enough, I would end up back where I began.

Well this question is sort of like that. As if you were inside a gazing ball, and no matter where you looked, anything at the far edge was where you looked from and behind you.


Ugh.. it is so hard to put it into a 3D term.

Maybe I should just give up before I even start.

[Peter Wilson]

Einstein played around with some model universes that curved back on themselves. You might be thinking of those. It has been well established for a long time, however, that the "real" universe is flat, i.e. does not curl back on itself.

[EvilEye]

O.K... now I am learning.

Flat in relation to what?

3D flat? or 4D flat?

[Argos]

I have entertained myself with this question for a while.

Light orbits a black hole at the event horizon. A ray of light can be bent to some degree in other trajectories.

So, there could be an intermediate trajectory very close to the event horizon in which light would do a u-turn and head backwards in the direction of the source. It would be a gravitational mirror. In that case, we would be seeing objects where they are not, and even see duplicated objects in different regions of space. We could even see our milky way reflected back. That would have serious implications. That reflected light could be distorted, but the spectral signature would remain the same.

I posted something about it a while ago.

Gravitational Mirrors

[EvilEye]

That was a great read Argos! Thanks.

I'm glad that at least it is being thought about.

Perfect conditions for strange things are not that rare, especially when there is enough room for everything to happen.

[Argos]

I'm glad that at least it is being thought about.

Yeah, it would be like taking the spacetime warp to the ultimate consequences. It would be cool if somebody knowledgeable could expand on it.

[EvilEye]

Imagine for a second if our own planet's light went out and bounced back.

We could view our dinos walking around! (Hypothetically of course)

[Argos]

Yeah, I think such reflection would be mangled beyond recognition. But weŽd still have the spectral signature.

[John Mendenhall]

O.K... now I am learning.

Flat in relation to what?

3D flat? or 4D flat?

Yes, and yes, keeping in mind that there are local distortions surrounding massive objects.

You might try the WIKI article on manifolds. It's not as daunting as it seems at first. Just read through it, with delving into the math. The concepts of space (and spaces) will be much clearer.

[publius]

John,

Clean out your PM mailbox! Sorry to post here, but I'm hoping you see this. I've been trying to send a reply to you for several days......

-Richard

[mugaliens]

I have entertained myself with this question for a while.

Light orbits a black hole at the event horizon. A ray of light can be bent to some degree in other trajectories.

So, there could be an intermediate trajectory very close to the event horizon in which light would do a u-turn and head backwards in the direction of the source. It would be a gravitational mirror. In that case, we would be seeing objects where they are not, and even see duplicated objects in different regions of space. We could even see our milky way reflected back. That would have serious implications. That reflected light could be distorted, but the spectral signature would remain the same.

I posted something about it a while ago.

Gravitational Mirrors

The giveaway, however, is that no matter from what position this was observed, it would always appear as a thin, bright halo surrounding the black hole.

So we're not going to see any particularly strange mirroring effects other than from very certain points in space.

[Michael Noonan]

I have put the picture of the dark matter ring as my computer background an when you discount a few galaxies and a large bright event near the top of the picture it seems that if various spirals were constructed from out to in there appears to be a mirroring effect.

Has there been any talk on that?

[Argos]

The giveaway, however, is that no matter from what position this was observed, it would always appear as a thin, bright halo surrounding the black hole.

Yeah, but not all gravitational warpings produce rings or halos. You can also have point sources in deflected trajectories [as in the famous 1919 eclipse].

[mugaliens]

Yeah, but not all gravitational warpings produce rings or halos. You can also have point sources in deflected trajectories [as in the famous 1919 eclipse].

This was specific to inbound light coming infinately close to the event horizon of a black hole. Obviously at a distance it would merely appear as normal gravitational lensing.

[mugaliens]

What's the greatest change in trajectory in degrees of light around a black hole without falling into the event horizon?

Hint, if it spirals in more than 180 degrees, something's wrong.

Another hint - light trajectories around black holes remain parabolas (not eclipses).

Third hint - where would the apex of the parabola be?

Another question: If light is eminating from a distant object towards a black hole, how far around can it go before it impacts the event horizon?

[Argos]

What's the greatest change in trajectory in degrees of light around a black hole without falling into the event horizon?

Indeed, this is the very core of the argument in the OP [and in my idea of G mirrors]. And the fact that trajectories are parabolic or hyperbolic rule out mirrors.

Another question: If light is eminating from a distant object towards a black hole, how far around can it go before it impacts the event horizon?

A good one.

[EvilEye]

Well... even if we could only define the spectral signatures, we could still mistake our own planet shining back at us for another Earthlike world.

It would be a whole new and interesting form of ancient geology.

[mugaliens]

Well... even if we could only define the spectral signatures, we could still mistake our own planet shining back at us for another Earthlike world.

It would be a whole new and interesting form of ancient geology.

Yes, that would be interesting...

Unlikely, though, as we can probably discount all such emanating from the viscinity of a black hole.