
A Magnetic Wormhole (2015) - jotux
http://www.nature.com/articles/srep12488
======
civilian
If my memory from last year serves me, this is less a wormhole and more of a
"magnetically-shielded tunnel". Cool and potentially useful, but I wish they
didn't use the word wormhole.

~~~
gaur
> I wish they didn't use the word wormhole.

Taking a hot physics buzz-phrase (wormhole, black hole, Hawking radiation,
etc.) and applying it to a mathematically analogous (but physically unrelated)
system is currently fashionable in physics. Personally I find it kind of
dishonest, but it seems to be a popular strategy for focusing attention on
research that is otherwise only marginally interesting.

~~~
abdullahkhalids
You stated the valid reason why physicists do this naming. The mathematics is
analogous. This means that by studying the different system (eg. the wormhole
in the lab), the physicists are probing the mathematical structure of the
theory of the original system- except that studying the different system is
easier than the original system. Actual wormhole physicists then might learn
from this research to understand how wormholes might behave.

Why this is a recent trend is because only in the past few decades have
experiment technologies improved to the point where exotic systems can be
physically simulated in the lab using simple systems. My own research is
partly of this sort and so we have fancy names too, but I assure you that, at
least in my group, no one cares one bit about our research being published in
pop-sci magazines

~~~
gaur
> This means that by studying the different system (eg. the wormhole in the
> lab), the physicists are probing the mathematical structure of the theory of
> the original system

I just don't buy that argument, because it is essentially the same argument
that was used to support the ether hypothesis. Both sound and light are
governed by a wave equation. Since sound is observed to have a preferred frame
(the rest frame of the medium), the above argument asserts that light should
also have a preferred frame, since the mathematics is the same. But that line
of reasoning is obviously wrong, as we know now.

I don't think that observing some wormhole-like feature in a metamaterial
provides any information about how wormholes may or may not behave in GR. The
entire endeavor of analogue gravity seems specious to me.

~~~
abdullahkhalids
Science going wrong (ether) is not a bad thing. In fact, if scientists were
not routinely wrong, we would suspect there was something wrong with our
scientific method.

Let me challenge your argument more directly. Postulating ether after
observing that sound and light have similar properties (wave behaviour) is not
stupid. It is the logical thing to do. It was also a hypothesis. Scientists
did well-designed experiments and eventually realized that light does not a
need a medium to travel. The scientific process correctly identified
falsehood. Outcome: we are clear on which properties light and sound share
(wave equation) and which they don't (medium or lack thereof)

I haven't read the paper, but let me make a statement about metamaterial
wormholes. Metamaterial experiments in the lab might be able to simulate a
type of wormholes. If they can then we know that within another theory that
shares enough math with EM will also have wormholes of that type. The question
then is if GR has and EM share enough of that mathematical structure. If they
do then these types of wormholes will also exist in GR. This is a different
way of investigating GR wormholes then directly looking at the theory of GR.
The differences between EM theory and GR might make it easier to discover
wormholes in the former than in the latter.

TLDR; Let scientists get creative.

~~~
semi-extrinsic
> The question then is if GR has and EM share enough of that mathematical
> structure.

And how do we answer that question, other than directly looking at GR theory?
Moreover, even if we do find EM evidence in favor of wormholes, how do we know
quantum gravity doesn't prevent their formation?

~~~
abdullahkhalids
Yes. We will have to directly look at GR to verify. But as I said before, it
might be easier to do the investigation first with EM and then compare to GR
rather than look at GR directly.

We don't know what quantum gravity says. The job of the theorist to form self-
consistent theories and find the strongest predictions of these theories. When
we get experimental data we will find out which theories are falsified.

------
wyager
The interesting part of wormholes is that they introduce topologies that
connect two extrinsically "distant" points, yes? This research doesn't appear
to do that; it seems like it just "hides" the magnetic field for a distance.
The field still moves slower than light.

~~~
ars
The other interesting thing about wormholes is they don't exist, and can't
exist without basically rewriting every law of physics we have. They violate
almost every conservation law there is.

They are a mathematical curiosity, not a thing that could actually exist.

If you could rewrite the laws of physics there are lots of cool things you
could do, wormholes would just be the start......

~~~
derefr
It's the _creation_ of wormholes that would violate physics, though, right?
AFAIK our current model of physics would work just fine to describe a universe
that came into existence with permanent, stable wormholes already in it;
that'd just be part of its topology.

~~~
ars
No. Using them is the problem.

Say you are in a gravity well with one side of the wormhole, and the other
side is outside the well.

You could "lift" matter outside the gravity well without spending energy.

There are other problems as well: Gravity has no discontinuities, as objects
move, the gravitational field moves with it. You never have a situation where
gravity just suddenly shows up. (The same is true for an electrical field BTW
- you can never create one, you can only move an existing one (i.e. split up
the positive and negative parts). A magnetic field can be created, but that's
because you always create a north and south at the same time. If magnetic
monopoles existed you could not create just one, you could only separate the
two halves.)

Anyway, a wormhole would allow you to have a gravitational discontinuity and
that's impossible, it would create a gravitational wave with an infinite
frequency. As you know a true square wave is physically impossible - the
fourier transform requires an infinite frequency - but that's what you are
doing by moving matter via a wormhole.

~~~
derefr
> You could "lift" matter outside the gravity well without spending energy.

How is that? Wouldn't the gravitational force just propagate across the
wormhole, making for a continuous gravitational gradient?

Maybe we're talking about separate conceptions of what a "wormhole" is here.
For one example of what I'm picturing, you could have a one-wormhole universe
as a three-dimensional hologram along the surface of a 4D hypertorus. You can
go "through the doughnut hole" to get somewhere quicker than you could by
going "around the doughnut", but that doesn't mean that there's a
discontinuity anywhere on the surface of the hypertorus. Gravitational waves
from one point-source would be propagating both "into" the wormhole (along the
inside of the doughnut) and "through regular space" (along the outside of the
doughnut) and eventually encountering themselves at the destination and maybe
constructively or destructively interfering, but they wouldn't be forced into
a square wave at any point.

~~~
ars
> How is that? Wouldn't the gravitational force just propagate across the
> wormhole, making for a continuous gravitational gradient?

That would be even worse. Let a strong gravitational force go through the
wormhole and drop something near it (not through it).

Then move the wormhole (and the gravitational force) elsewhere, lift the
object, and bring the wormhole back.

Normally the thing that generates gravity has inertial mass, so it costs
energy to move. Not with a wormhole. If you speculate that it should have
inertial mass, then how much?

~~~
wyager
The solution to this is almost certainly "moving the wormhole takes energy and
solves this 'paradox'". The mass-energy of the wormhole could be from
gravitational field energy, for example.

~~~
ars
How much energy? The wormhole doesn't have an inherent mass, so how much
energy does it take? After all you can put an arbitrary amount of mass through
it.

~~~
wyager
You're looking at it the wrong way. If you can extract energy from dropping
the rock through the wormhole, it takes energy to pull the rock away from the
wormhole (and, by symmetry, it takes that much energy to move the wormhole
away from the rock).

------
exabrial
Reminds me of a sci-fi movie I can't think of the name of... they end up on a
ship and it's haunted or something

~~~
ugh123
Event Horizon
[https://en.wikipedia.org/wiki/Event_Horizon_(film)](https://en.wikipedia.org/wiki/Event_Horizon_\(film\))

~~~
exabrial
Yes! That's it. Well I got down voted so many times the movie must really not
be a crowd favorite :D

~~~
ConceptJunkie
Maybe because the movie took a potentially awesome premise and totally whizzed
it by turning it into a lame remake of Star Trek episode.

