Why the explanation of wormholes using paper grinds my gears

[Alex Petrosyan]

Hey, This is more of a discussion rather than a question.

A lot of movies (e.g. interstellar, Event Horizon), have a go at trying to explain how the Warp/Alcubierre drive could work, and usually, the argument goes like this:

They take a point A and a point B, connect them with a line on the sheet of paper, and say " that's going from A to B conventionally". Then they fold the paper in two, make the two points right on top of each other, punch a hole, and say "That's how a wormhole works".

My problem is, that's not how any of this works! Folding a sheet of paper and punching a hole through it requires an extra spatial dimension, and implies you can fold the ENTIRE universe in that fashion. The Alcubierre drive as well as the wormholes work completely differently: a wormhole works in 4D space-time, by changing said space-time's intrinsic curvature. Am I incorrect, or is it really an oversimplification?

 

[jbriggs444]

Am I incorrect, or is it really an oversimplification?

If one is trying to explain a non-trivial topology to a lay audience, it is far easier to talk about a scaled down two dimensional space embedded in a three dimensional Euclidean space than to talk about a four dimensional pseudo-Riemannian manifold without an embedding.

 

[Ryan_m_b]

Good science communication conveys concepts as accurately as possible. A lay audience would not understand a lecture on wormhole theory based on 4D space-time curvature, hell most scientists wouldn't understand beyond the physicists. Therefore whilst you might have upped the correctness of an explanation you have actually performed worse at communication by not making it comprehensible.

The folded paper analogy works absolutely fine for conveying everything about a wormhole that a layperson needs to understand to follow the story: that it's an object in space that connects two distant places together that the protagonists can travel through.

 

[Alex Petrosyan]

Yeah, but there's a better way: take a piece of modelling clay and make it slightly flat. Then mark two points and squeeze them together. That would describe a wormhole/Warp drive. What they do is something different: they describe a hyperspace engine that uses an extra spatial dimension. It's basically, as bad as calling lightsabers "laser swords".

 

[Ryan_m_b]

Yeah, but there's a better way: take a piece of modelling clay and make it slightly flat. Then mark two points and squeeze them together. That would describe a wormhole/Warp drive. What they do is something different: they describe a hyperspace engine that uses an extra spatial dimension. It's basically, as bad as calling lightsabers "laser swords".

Aside from how weird it would be for scientists/soldiers on a spaceship to have some modelling clay to hand that explanation is going to give the wrong impression in a practical sense, even if it is more technically correct. Pushing two areas of modelling clay together will make the viewer think that the wormhole is pulling another location closer, so they might expect that if the wormhole drive is activated from Earth to Neptune that the latter will be pulled to the former.

The practical details are far more relevant to the audience than technical details. If you don't have a way that can convey both clearly go for the former, not the latter. Or you end up with bad fiction. But this also applies beyond fiction as well to any branch of science communication to people outside the field.

 

[Alex Petrosyan]

Yeah, modelling clay, may be a problem, but rubber wafers and bread - not so much.

Secondly, if the writers want something that works like folding paper, they should call it what it is: a hyperspace drive, rather than what it isn't - a wormhole.

An FTL technology, if it's named after something that is kinda real (i.e. a warp drive, an Einstein Rosen Bridge), should give you the right intuition about the real deal. I'm supervising students in GR and trying to get them to understand that this description is a complete misnomer, is a tough sell. They quote however many people worked as scientific advisors for interstellar, and say that I'm wrong. And that's a problem!

 

[essenmein]

I thought the warp/Alcubierre drive was different conceptually to einstein rosen bridges?

I thought the Alcubierre in laymans terms depressed space time infront of it pulling it along inside a little bubble of its own space time leading to linear FTL, vs the rosen bridge which is the worm hole "jump drive" idea?

I thought in warp a ship could still "crash" into stuff on the way, where a einstein rosen bridge would not do that?

 

[Alex Petrosyan]

They are. The way I understand it, is as follows:

1) A Warp/Alcubierre drive is a bubble which isn't moving through ST, but Warping it. If something is on the path from A to B, it might get deformed. You should be fine, though.
2) A wormhole (ER-bridge) is like a tunnel from A to B. That is, both A and B are at the same point in that space-time. So you basically teleport from A to B, But this is more like a StarGate, rather than a jump drive. It's also a 3surface, which Interstellar did actually get right.
3) A hyperspace drive means going into extra dimension(s) and without deforming space-time intrinsically, rather by folding it like paper reaching your destination.

So my biggest issue is that those 3 are confused. My students think that it's impossible to have 1 and 2 without extra spatial dimensions, and confuse extrinsic curvature with the extrinsic curvature from the embedding hyperspace.

I realize that this is basically just venting, but maybe one of the scientific advisors to one of those movies should have said "let's keep this technology a mystery".