Worm holes, ftl and time travel:

Physicist suggests some types of wormholes may stay open long enough to send a photon through:

University of Cambridge physicist Luke Butcher has uploaded a paper to the arXiv preprint server suggesting that there might exist some type of wormhole that is capable of staying open long enough for a photon to pass through—which of course suggests the possibility of sending messages backwards or forwards in time.

Read more at: http://phys.org/news/2014-05-physicist-wormholes-photon.html#jCp

EXTRACT:
He suggested that wormholes might be kept open though the use of negative energy, aka Casimir energy. While the idea seemed promising no one was able to think of a way to cause the creation of Casimir energy to occur inside a wormhole, while a human vehicle passed through. In his paper, Butcher suggests that there might be another way—by taking advantage of Casimir energy that exists naturally in some wormholes. He did a lot of calculating and found that if a wormhole was a lot longer than it is wide, the amount of Casimir energy present inside of it would be enough to cause it to stay open longer than normal. Just long enough, Butcher suggests, to send a photon through.

Read more at: http://phys.org/news/2014-05-physicist-wormholes-photon.html#jCp

 

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http://arxiv.org/abs/1405.1283v1

Abstract:
We calculate the Casimir energy-momentum tensor induced in a scalar field by a macroscopic ultrastatic spherically-symmetric long-throated traversable wormhole, and examine whether this exotic matter is sufficient to stabilise the wormhole itself. The Casimir energy-momentum tensor is obtained (within the R×S2 throat) by a mode sum approach, using a sharp energy cut-off and the Abel-Plana formula; Lorentz invariance is then restored by use of a Pauli-Villars regulator. The massless conformally-coupled case is found to have a logarithmic divergence (which we renormalise) and a conformal anomaly, the thermodynamic relevance of which is discussed. Provided the throat radius is above some fixed length, the renormalised Casimir energy-density is seen to be negative by all timelike observers, and almost all null rays; furthermore, it has sufficient magnitude to stabilise a long-throated wormhole far larger than the Planck scale, at least in principle. Unfortunately, the renormalised Casimir energy-density is zero for null rays directed exactly parallel to the throat, and this shortfall prevents us from stabilising the ultrastatic spherically-symmetric wormhole considered here. Nonetheless, the negative Casimir energy does allow the wormhole to collapse extremely slowly, its lifetime growing without bound as the throat-length is increased. We find that the throat closes slowly enough that its central region can be safely traversed by a pulse of light.
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Please accept my apologies for my sensationalistic style title.

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But like any scientific discovery, this could have potential for a future advanced civilisation.
Plus in a way it aligns with some speculative ideas that I have about Worm Holes, BH's WH's and ERB's.

 

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This is woo, paddoboy. Don't think it isn't just because it's from a Cambridge physicist. Time travel is science fiction. Read what I said and understand why it's science fiction. Then you will understand that a wormhole which "suggests the possibility of sending messages backwards or forwards in time" is science fiction too. But cringe. I know what you'll say. You'll find some specious reason to dismiss the hard scientific facts and the evidential physics I give you because you love your woo so much. What was it you said? Oh yes:

Paddoboy believes in woo and dismisses physics. Sigh. Oh the irony. Oh the ignorance. No wonder he's talking to himself.

 

paddoboy, below is the whole article that you quoted except the extract - which you already Posted. I highlighted a few words in the Quote that should not be overlooked in the article!

- ^^above quoted^^ from : http://phys.org/news/2014-05-physicist-wormholes-photon.html#jCp


paddoboy, at best this article possibly could be called "speculative fiction", and honestly should not be Posted in the "Astronomy, Exobiology, & Cosmology" Forum.

paddoboy, I have to agree with Farsight on this one, you should "practice what you preach" and Post all speculative "WOO" in the appropriate Forum!!

 

Really interesting work. They chose a wormhole geometry but I think they can probably apply the same analysis for warp geometry. When the energy density goes to 0 the geometry will collapse. It's really interesting when they tell you how long that will take. Thanks for posting .

 

Firstly Farsight, my "woo" as opposed to your own woo, is not disallowed by GR and the laws of physics.
And no, time travel is not THEORETICALLY Impossible...but I wont go into the why's and wherefors about that now.

Your own nonsensical thoughts are in my opinion, highlighted by the fact that you Imagine time is seen to stop at the EH of a BH. That really is crazy talk.
Time in the local frame, for someone crossing the EH, proceeds as per normal.....The time factor in that frame, from the PoV of an outside FoR, is just seen to slow down and gradually red shifted, further and further along the spectrum, until disappearing, but never quite stopping, and never actually seen to cross the EH.
You got picture.

 

Like I said, my "woo"is not disallowed by GR and the laws of physics.
The article is in the appropriate section due to that fact.
If you have any troublesome qualms about that, you know what you need to do. :shrug:

Bye bye dmoe

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No probs brucep....Nice to discuss relevant cosmological matters with someone with some knowledge.
Although wormholes are allowed by the laws of physics and GR, one must ask the question, why have we not ever seen any.
Perhaps their rarity?? Maybe they are only in existence inside BH EH's at the Singularities....I'm alluding to ERB's of course.

Kip Thorne discusses them in detail in his book, "Black Holes and Time Warps"

And of course wormholes if they do exist, could very well be a vehicle to facilitate time travel.........
Obvious problems though do exist before that can be achieved.

 

Supplementary Article:
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http://phys.org/news192818490.html#nRlv

Seventy-five years ago, Albert Einstein and his collaborator, Nathan Rosen, submitted a paper to the Physical Review with the goal of unifying gravity and electromagnetism. Although they failed to discover a theory of everything, they did something arguably more much important: By creating the first theoretical model of a wormhole, Einstein and Rosen allowed science-fiction writers -- including Arthur C. Clarke, Madeleine L'Engle and the writers of "Babylon 5" and "Doctor Who" -- to explore vast stretches of space and time in the blink of an eye.
From the outside, an Einstein-Rosen bridge, as wormholes were originally known, looks a lot like its cousin, the black hole. And I risk having my official Physics Badge revoked if I don't tell you, ideally in a spooky voice, that "nothing can escape from a black hole -- not even light."
Einstein and Rosen made a very bold supposition: What if a traveler fell into the mouth of something that looked like a black hole, but rather than being crushed by a singularity at the center of a black hole, instead emerged from another mouth, potentially many light-years from where he or she started? This isn't as crazy as it sounds. Einstein's theory of general relativity -- our current working model for how gravity and space work -- has been confirmed with countless experiments. And, as ad hoc as it sounds, an Einstein-Rosen bridge is a perfectly valid solution to the equations of general relativity.


Read more at: http://phys.org/news192818490.html#jCp
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Naturally, ideas re wormholes, and time travel are many and varied, but unlike the real "woo" and misinterpretations of remarks of giants of the past, and the fairy tale conclusions realized from such misinterpretations, wormholes and subsequent time travel of sorts are not forbidden by GR and the laws of physics.

That makes them legitimate discussion material in the cosmology thread, for legitimate physicists/cosmologists and interested lay people.

 

@ paddoboy

Unicorns, Fairies, Worm Holes, Time Travel...et al - none of them are "forbidden by GR and the laws of physics"!

Just because something is NOT "forbidden by GR and the laws of physics" means that they can or ever will be manifest in Reality!

Hence, just because something is NOT "forbidden by GR and the laws of physics" does not make it any less "Speculative Fiction" than the existence of Unicorns, Fairies...etc.
Ergo, "Woo" is "Woo" - no matter how much "Lipstick you put on that Pig"!!!

 

EPR...and interpretations.

It's a very intriguing topic! I wonder what Albert would make of "modern" QM theory?

It's very nice to have calculus around...it sure makes things a lot easier to explain!

I hope that someday I too will understand enough to be able to "figure" everything out!

For right now...I'm pretty much hopeless...can anyone post a "link" for me where there is a "wormhole?" Or a photo of a "black-hole?" I cannot find any...there must be a

location somewhere!


(Thanks for reading!) p.s. hi Lunny.

 

You are entitled to believe in your Unicorns, Fairies as much as you like...no skin off my nose, but you need to actually stick to science for science's sake, and not let "personalities" get in and cloud your thinking.

GR concerns itself with space/time manipulation and warping, curving, twisting etc.
That obviously also takes in wormholes and BH's, as well as other aspects like WH's that I have discussed in the cosmology section before.

But if you think you have a case, go for it my friend!

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BH's, and wormholes by their very nature, cannot be seen...They are inferred by their effects on space/time and matter/energy in their vicinity.

Of course if you doubt BH's exist, then you need to come up with an hypothesis that can describe the effects we do see.
Wormholes of course have not as yet been found. But they are a prediction of GR and the phenomenal success of that theory, would consequently see wormholes as a distinct possibility.

 

Therein lies the rub, paddoboy I prefer NOT to "believe in Unicorns, Fairies, Worm Holes, Time Travel...et al"!!

paddoboy, this "twisting" you refer to...is it similar to the "twisting" of Reality, Science, Logic, Intelligence and just plain Common Sense that seems to Persistently Permeate the Preponderance of paddoboy's Puerile Posts?

Just asking?

P.S. since you mentioned your "nose" and "personalities"!
Question : Do you know the difference between a "Butt Kisser" and a "Brown Noser"?
Answer : Depth Perception!

 

Is that right?
But you still havn't validated your original claim, nor invalidated GR.
I'm sure the mods here would move this thread, if it was needed, just as they moved others when it was needed.
But its not needed....Therein lies the rub.
A few things you must realise dmoe, [1] speculation and Imagination are part of science...[2]Don't though, put them as facts [as some are apt to do]...[3]Common sense and logic says the same Imagination and speculation, must at least be allowed or permitted by the laws of physics and GR....[4] wormholes and time travel of sorts are not forbidden.



Getting back on track...
Here's another Interesting article.
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Wormhole Is Best Bet for Time Machine, Astrophysicist Says:

Traveling forward in time is an uncontroversial possibility, according to Einstein's theory. In fact, physicists have been able to send tiny particles called muons, which are similar to electrons, forward in time by manipulating the gravity around them. That's not to say the technology for sending humans 100 years into the future will be available anytime soon, though.

Time travel to the past, however, is even less understood. Still, astrophysicist Eric W. Davis, of the EarthTech International Institute for Advanced Studies at Austin, argues that it's possible. All you need, he says, is a wormhole, which is a theoretical passageway through space-time that is predicted by relativity. [Wacky Physics: The Coolest Little Particles in Nature]

more at...
http://www.livescience.com/39159-time-travel-with-wormhole.html
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Finally, paddoboy, you Post an "Honest to God" truthful statement : that I, dmoe, "still havn't invalidated" my "original claim".

Not only have I not "invalidated" that "original claim", no one else, including yourself, paddoboy, has "invalidated" that "original claim" either.

So... paddoboy, my "original claim", as you put it, is still Valid, and will remain Valid.

 

My mistake....
That should have been of course "YOU HAVE NOT VALIDATED YOUR SILLY ORIGINAL CLAIM" mea culpa, mea culpa, mea maxima culpa.
Or the fact that GR does not disallow wormholes and/or time travel.

Now are you going to try and invalidate my claim and the claim of GR?

 

If that was true, this thread would be moved, would it not?
Or are you now going to claim conspiracy???

 

Now that's better...
Again dmoe, mea culpa for inferring you were anything other then wrong....mea culpa.