What does relativity say about wormholes?

[Gear300]

I would like to think this is a legitimate question in the fold of Relativity theory. It originally started with the idea that

"If someone were to wormhole themselves 2000 or so light years away and turn their sights back on the Earth, they could possibly get a glimpse of the Crucifixion?"

On a similar note without the wormhole, if we somehow manage to expand ourselves to 2000 light-years away in the next 2000 or so years, then we might be able to glimpse back at today.
What I know of Relativity is that as interesting as it does make of space-time, it does not defy notions of causality any more than Newtonian space-time. So returning to the question of wormholes, I figured it was something of an "analysis-synthesis" sort of thing. In other words, there are no known processes in the observable universe that can churn a wormhole, but they can exist as solutions a priori in Relativistic space-time. But I find their existence confounding either way, since if the 2000 light-year wormhole existed, then (1) either the time upon exiting the wormhole will be consistent with 2000 light-years away, so that wayfarers actually time traveled into the future through the wormhole, or (2) the above scenario in quotation marks. So my question is, without having studied Relativity, what do supposed wormhole solutions actually make of space-time?

 

[Vanadium 50]

There are no stable traversable wormhole solutions involving ordinary matter. Does that answer your question?

 

[phinds]

"If someone were to wormhole themselves 2000 or so light years away and turn their sights back on the Earth, they could possibly get a glimpse of the Crucifixion?"

if we somehow manage to expand ourselves to 2000 light-years away in the next 2000 or so years, then we might be able to glimpse back at today

They would have to have one hell of an optical system since 2000 light years away means that the optical signal would be few photons at best and that's assuming they even made it past the atmosphere. This is a pipe dream.

 

[Gear300]

They would have to have one hell of an optical system since 2000 light years away means that the optical signal would be few photons at best and that's assuming they even made it past the atmosphere. This is a pipe dream.

True. Although I figured maybe even something non-optical, since with the discovery of gravity waves, wikipedia now includes gravity waves as a form of radiant energy.

There are no stable traversable wormhole solutions involving ordinary matter. Does that answer your question?

Not that I'm trying to be presumptuous, but what do the unstable solutions say of the supposed paradox?, or is that besides the point?
You could say that the grounds for me asking is that a lot of sci-fi makes use of the warp drive. So if we were to shun warp drives from sci-fi on account of science, we would be shunning a good deal of Star Trek and Star Wars.

 

[malawi_glenn]

supposed paradox?

https://www.physicsforums.com/insights/how-to-avoid-breaking-physics-with-your-what-if-question/

 

[Vanadium 50]

You asked what GR said. GR says the setup you described is impossible.

 

[Ibix]

You could say that the grounds for me asking is that a lot of sci-fi makes use of the warp drive. So if we were to shun warp drives from sci-fi on account of science, we would be shunning a good deal of what is originally American sci-fi.

The idea of this forum is to discuss real science - warp drive solutions and wormholes are kind of borderline because they are seriously discussed, but there are a lot of issues with them.

As far as I'm aware, if wormholes that are traversable could be created there's no particular reason why the exit has to be at the same "time" as the entrance. In fact, there's no clear global definition of time in that sense in relativity. Furthermore, there certainly are spacetimes that include "closed timelike curves", paths that close back on themselves so that their past is their future. So being able to see yourself in the past is certainly something allowed by relativity. Whether such spacetimes are realistic or not is debatable, but GR doesn't appear to fprbid them.

 

[Gear300]

https://www.physicsforums.com/insights/how-to-avoid-breaking-physics-with-your-what-if-question/

Lol, I'll bear this in mind.

You asked what GR said. GR says the setup you described is impossible.

The idea of this forum is to discuss real science - warp drive solutions and wormholes are kind of borderline because they are seriously discussed, but there are a lot of issues with them.

As far as I'm aware, if wormholes that are traversable could be created there's no particular reason why the exit has to be at the same "time" as the entrance. In fact, there's no clear global definition of time in that sense in relativity. Furthermore, there certainly are spacetimes that include "closed timelike curves", paths that close back on themselves so that their past is their future. So being able to see yourself in the past is certainly something allowed by relativity. Whether such spacetimes are realistic or not is debatable, but GR doesn't appear to fprbid them.

So I guess they are mostly just a fancy, or a stretch of the maths.
At the very least, we can be sure Relativity has its limits and that quantum descriptions have to pitch in at characteristic limits.

 

[Vanadium 50]

I don't know what this means.

 

[Ibix]

So I guess they are mostly just a fancy, or a stretch of the maths.

There are known solutions with wormholes, but I don't think they are in realistic spacetimes. And there's a very strong element of "can't get there from here" in many solutions of Einstein's equations - you can write down spacetimes with all sorts of properties, but you can't make our spacetime look like that. So in a sense, yes, they're just mathematical games that physicists play. But interesting and useful stuff sometimes comes put of such games.

At the very least, we can be sure Relativity has its limits and that quantum descriptions have to pitch in at characteristic limits.

I don't really understand what you mean here. Certainly GR is not a complete theory of our universe, and we expect a quantum theory of gravity to work in a wider range of circumstances and possibly eliminate some of the problems GR has with singularities. This isn't related to wormholes as far as I am aware.

 

[collinsmark]

Certainly GR is not a complete theory of our universe, and we expect a quantum theory of gravity to work in a wider range of circumstances and possibly eliminate some of the problems GR has with singularities. This isn't related to wormholes as far as I am aware.

They might be related! Well, maybe. According to Leonard Susskind, who, together with collaborators who have been contemplating and studying the idea for the last several years, thinks they might be.

The concept is called "ER = EPR" (spoken as "ER is EPR"), and is a conjecture that entangled particles (Einstein-Podolsky-Rosen pairs) are connected by a wormhole (Einstein-Rosen bridge).

Of course, these wormholes are microscopic; not the kind of thing that will allow you to transport your entire self 2000 ly away. But the theory might, maybe, one day help form a basis for a theory of quantum gravity.

Doing a google search on "ER = EPR" is enough to get you several Susskind (among others) lectures on the subject.

 

[john.phillip]

There are no stable traversable wormhole solutions involving ordinary matter. Does that answer your question?

The stability problem is only applicable to static wormholes. Rotating wormholes are self-stable and do not require any sort of magic to keep the throat open.