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So finally you possess that most valuable of commodities, a traversable wormhole – and somehow or other you grab one end of it and accelerate it to a very rapid velocity.
This might only take you a couple of weeks since you accelerate to the same velocity as your end of the wormhole. But for a friend who has sat waiting at the first entrance to the wormhole, time dilation means that ten years might have passed while you have mucked about at close-to-light-speed-velocities with the other end of the wormhole.
So when you decide to travel back through the wormhole to see your friend, you naturally maintain your own frame of reference and hence your own proper time, as is indicated by observing the watch on your wrist. So when you emerge at the other end of the wormhole, you can surprise your ageing partner with a newspaper you grabbed from 2011 – since he now lives in 2021.
You encourage your friend to come back with you through the wormhole – and traveling ten years back in time to 2011, he spends an enjoyable few days following his ten year younger self around, sending cryptic text messages that encourages his younger self to invent transparent aluminum. However, your friend is disappointed to find that when you both travel back through the wormhole to 2021, his bank account remains depressing low, because the wormhole is connected to what has become an alternate universe – where the time travel event that you just experienced, never happened.
You also realize that your wormhole time machine has other limits. You can further accelerate your end of the wormhole to 100 or even 1000 years of time dilation, but it still remains the case that you can only travel back in time as far as 2011, when you first decided to accelerate your end of the wormhole.
But anyway, wouldn’t it be great if any of this was actually possible? If you looked out into the universe to try and observe a traversable wormhole – you might start by looking for an Einstein ring. A light source from another universe (or a light source from a different time in an analogue of this universe) should be ‘lensed’ by the warped space-time of the wormhole – if the wormhole and the light source are in your direct line of sight. If all of that is plausible, then the light source should appear as a bright ring of light.
In fact there’s lots of these Einstein rings out there , but a more mundane cause for their existence is generally attributed to gravitational lensing by a massive object (like a galactic cluster) situated between you and a bright light source – all of which are still in our universe.
A recent theoretical letter has proposed that a ringhole rather than a wormhole structure might arise from an unlikely set of circumstances (i.e. this is pure theory – best just to go with it). So rather than a straight tube you could have a toroidal ‘donut’ connection with an alternate universe – which should then create a double Einstein ring – being two concentric circles of light.
This is a much rarer phenomenon and the authors suggest that the one well known instance (SDSSJ0946+1006) needs to be explained by the fortuitous alignment of three massive galactic clusters – which is starting to stretch belief a little… maybe?
Whether or not you find that a convincing argument, the authors then propose that if a Klein bottle wormhole existed – it would create such an unlikely visual phenomenon (two concentric truncated spirals of light) that surely then we might concede that such exotic structures exist?
And OK, if we ever do observe two concentric truncated spirals in the sky that could be pause for thought. Watch this space.
Further reading: González-Díaz and Alonso-Serrano Observing other universes through ringholes and Klein-bottle holes.
Of course this is a good way of testing whether or not the universe makes sense or not. If wormholes exist it means the universe has an intrinsically nonsensical structure. The Israel-Lansocz junction condition at the wormhole opening requires a quantum field that has not bounded quantum field eigenstates. This is due to the violation of the T^{00} >= 0 energy condition for these types of solutions. If the universe does ultimately make sense this way, the theoretical work would be a far greater difficulty.
The Klein bottle idea is somewhat interesting, for if in the 10-11 dimensional superspace there are wormholes of this type it might be that on compactification these become orientifold structures. In the very early moments these may have existed as quantum fluctuations or off-shell “gadgets,” which correspond to nonoriented wrapping of D-branes at lower energy.
LC
A most interesting object discovered !
With 3 different Redshifts to its 3 components, perhaps a reexamination of what causes Redshift is in order, rather than a speculation that makes my postings look normal.
“The main lens lies at redshift z=0.222 , with the inner ring at z=0.609 with an Einstein radius RE=1.43±0.01 and magnitude m=19.784±0.006 , the outer ring is at z?6.9 with RE=2.07±0.02 and magnitude m=23.68 ± 0.09.”
Um. Anything that suggest fairies instead of physics doesn’t look “normal”. Anything that suggest that tearing down already predictive and accepted physics would mean alternatives are somehow tested and useful doesn’t look “normal”.
I think you have to deal with that, as well as being horrendously wrong on physics (besides being horrendously wrong on science process as per the two counts above), see comments below.
There are three objects at different redshifts in the same line of sight. SDSSJ0946+1006 appears as one object, but it consists of three.
This is a compound gravitational lens. The different redshift values to the three components is a good indicator of that.
LC
That is optimally nicely put, I think. Physically wormholes have the makings of fairy tales; yes, they would work, but we have ordinary physics explaining what we see. (Re the usual analogy of fairies pushing around electrons in television sets.)
That said, we can say more on wormholes than fairies.
First, on the unraveling to nonsense. We can see from Aaronson’s work (“NP-complete Problems and Physical Reality”, Scott Aaronson) that time travel is very much forbidding for “sensical structure” [sic!]. The post explains rather well how we have to remove wormholes surgically from physics, at least from on-shell as LBC notes, to heal the patient; no time travel means no wormholes.
Interestingly time travel is so forbidding that a classical mechanics paradox is enough to see that general relativity isn’t self-consistent with it:
“Acceleration of one of the wormhole mouths can introduce a time delay which transforms the wormhole into a time machine.
In this case we have to address the “Polchinski paradox”[12]. Consider that a billiard ball falls through a wormhole, travels back in time, and collides with its younger self, preventing it to fall in the wormhole in the first place. Similar paradoxes have been obtained by Rama and Sen[13] when they considered collisions of objects of different mass.
There is only one way to avoid those paradoxes: eliminate the initial conditions that can lead to them[13].”
Second, on the acceptance of intrinsically nonsensical structure. We can see from environmental principles that without paradoxes like the Polchinski paradox, which may or may not be finetuned, that environmental principles could save volumes with structures that makes physical sense.
But outside of causality of spacetime volumes we retain ordering by time alone as a powerful concept. I don’t see how we can reject that meaningfully, or retain it without running up against paradoxes like Polchinski’s.
So after saying more on wormholes than fairies we have to return to our ordinary supervised tour of the universe anyway. Good thing the universe isn’t anything like mundane with complex, sensible structure in it!
Added after revising:
“complex, sensible structure”. I mean, look at those bootyful Einstein rings!
Wormholes can be accelerated in various ways to generate time machines, or spacetime regions with closed timelike curves. There have been some complicated arguments given for why causality violations are avoided. However, these arguments are much more complicated than saying wormholes do not exist. Why they do not exist is potentially an important puzzle piece in the problem of quantum gravity. These issues have some relationship with nonlocality in quantum mechanics along time reversed directions, and in more completeness the Hardy problem in quantum measurement.
LC
It would be interesting to find a way to deconvolute the image somehow and actually see that farthest object!
I looked very carefully at this image and blew it up several hundred times and swear I distinctly saw a little kid waving out a window.
@Aqua:
“It would be interesting to find a way to deconvolute the image somehow and actually see that farthest object!”
A reconstruction of the galaxy appearing as the bright inner ring at z=0.609 (Ring 1) can be found here: http://arxiv.org/PS_cache/arxiv/pdf/0910/0910.0760v2.pdf
The efforts to ‘fit’ the lensed galaxy were made difficult in part by the presence of the second distant source (‘outer’ Ring 2 with z around 6.9).
Reconstruction of Ring 2 is also problematic. In the 2008 study by Gavazzi et al no measurable emission lines in its’ spectrum could be detected, despite a heroic 9 hour integration using Keck. The photometric redshift of Ring 2 is only an upper limit based on previous Hubble imagery.
(2008 Gavazzi paper: htp://arxiv.org/PS_cache/arxiv/pdf/0801/0801.1555v1.pdf )
Excellent! + Thanks!
I don’t understand why there is such a fascination about time travel. If it were true, as often and commonly quoted in various forms, then where are all the time travellers?
IMO time travel fails only in the understanding in how time manifests itself. Concerns for me are not in the macro world (in relativity, for example) but in how time is working on a quantum level.
The main story here focuses on the function of time in a wormhole in the macro sense, and while it is mathematically fascinating, the practicality of actually doing it (or even surviving it) is next to impossible. Again, many of these theories fail (IMO) because we do not yet comprehend even how quantum mechanics actually works inside wormholes. (There is a possibility violation of time travel is prevented by probability functions under these extreme conditions. I.e Where possible time generation by some process in the quantum mechanical world just does not work.)
In honesty, I don’t quite understand the essential nuances of the problems here, both mathematically and the theoreticians working on such subjects, but it seems there remain interesting issues in comprehending how time is actually manifested. It is probably the ultimate barrier left before achieving the ‘Theory of Everything.’
Wormholes are an interesting thought experiment, but they still remain observationally elusively and unproven in nature. I fear they will remain as such.
There are some deep issues. The one thing is the Einstein field equations permit spacetimes with closed timelike curves. There is nothing about general relativity which precludes these things. This may be analogous to the anomalous solutions of the Abram-Lorentz equations in electromagnetism, which lead to runaway solutions. Look up the Wheeler delayed choice experiment, where the establishment of an experimental choice at a time t can determine the quantum configuration at a time t’ < t. This is not a time loop though, for no actual information is communicated. The Hardy paradox between pre and post selected states of measurement illustrate some similar oddities. Somehow these quantum physics results provide blockers to the actual communication to information backwards in time. So the issue of time travel is not so much interesting from an HG Wells perspective, but in framing issues with the foundations of the universe.
LC
Would it be possible to detect a nearby low mass black holes via a similar method? That is to say to look for stellar objects with circular distortions against the b/g sky?
(s)
Do Neutron stars or Magnetars create ‘micro’ Einstein lens around them? What resolution would be req’d to see that?
Look up microlensing. It is used to find small local gravity sources, even brown dwarfs.
LC