Can we pinpoint location of a star after its light curved through space?

[mooeypoo]

Hi again guys,

 

I have a question that's been bothering me for a while. I can't seem to find a definitive answer - a lot of sites explain about the fact that we are aware light is being twisted and curved on its way through the universe and towards our eyes, but none really explains how we manage to - despite that fact - figure out WHERE exactly the original object really is.

 

I know that the color spectrum of a star visible to us tells us the curvature of its lightwave -- so that we can "uncurve" it.. or, at least this is what I could understand. What happens, however, if something goes through a few curvings? Light curves when it approaches space objects (other stars / black holes obviously) -- how do we know what was the original position of this star?

 

I'm really confused about this, so just in case my question is confused like me, I add a little drawing. This is done in windows paint so it's quite not artistic

 

 

You can see what I mean (I hope): The original Star emmits light towards us. This light SHOULD have gone on a straight line, and we would've been able to pinpoint it. However, two large bodies in space (just to show my point) curved the light twice, causing it to "travel" through space on the light-green curved line. We look at the light, and see the star where the blue spaced-line is, and pinpoint a wrong position.

 

I would imagine that since the color of the curved light is different than white, we might be able to curve it back to approximately where the real star is, but -- are we? How can we know the ammount of times the light is curved? I gave a "simple" example, where the light is only twice curved and not too much curving.. but when the star is billions of light years away --- can we really pinpoint it's EXACT location, or are can we just be wrong..?

 

Thanks in advance for any help with this.. quite baffling to me

 

~moo

[Sisyphus]

My guess is you could uncurve it just the way you describe, because you know how much it curves and the objects doing the curving. I don't actually think it would be any (or at least not much) harder if the object is far away, since you don't really have to calculate the effect of every single object in the way (e.g. millions of stars), because you can treat large groups of them as single objects, as far as gravitational effects are concerned. As in, the whole galaxy could be one object with such and such varying density, instead of millions of individual point sources. Thus there would be a limit to the complexity of the calculations that would be within managable limits. I guess it wouldn't be EXACT, but I wouldn't be surprised if the margin of error was negligible.

 

Of course, this is all just uninformed speculation....

[mooeypoo]

I wouldn't be surprised if the margin of error was negligible.

I hope you're right but I'm not all that sure.. what if my drawing would be an entirely curvy snake-like line? In such vast distances, it's possible.. would we really been able to pinpoint it?

 

And concidering the fact a lot of our hypothesis on space and its behaviour has to do with those stars, and their location/movement/distance, i wonder if perhaps the possibility that we may be wrong in pinpointing some of them wouldn't change our basic assumptions and conclusions about other things about space...

 

~moo

[SkepticLance]

It is a moot point as to whether the effects you are talking about actually matter in any current practical sense. The effect is enormously tiny, if that makes sense. Of course, if you actually travelled a few hundred light years to another star, the error would add up. However, I cannot see myself undergoing such a journey in the near future...

[bogie]

It is a moot point as to whether the effects you are talking about actually matter in any current practical sense. The effect is enormously tiny, if that makes sense. Of course, if you actually travelled a few hundred light years to another star, the error would add up. However, I cannot see myself undergoing such a journey in the near future...

Gravity lensing makes it possible to see multiple images of the same object.

 

It also can magnify the object. This graphic is exagerated to show the magnifying affect; the link describes it.

 

[Sisyphus]

The objects in those pictures are distant galaxies, so it does demonstrate just how much mass is needed to make any noticable difference, and also how those differences can obviously be compensated for.

[jgmaynard]

My thought would be that you could extrapolate the curve that the object would have to lie on, and that there would only be certain places along that curve where it could lie to cause the effect.

Now: multiple bendings? My SWAG is that it would get more and more difficult to calculate with each object the light passes by, creating a "three-billiard-ball" type of problem.

 

JM