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In movie "Interstellar", the wormhole is elaborately depicted as a sphere, complete with an explanation about why it is spherical, and as it is approached, it looks like a sphere containing fabulous galaxies etc.

While it appears to make sense that the spatial manifestation of a wormhole would be spherical, I can't see why a wormhole would "look like" anything at all.

If I have anything approaching a reasonable mental model, a wormhole is simply a region of space that has the property that if you traverse it you arrive at a different place in space than your apparent 3D trajectory would suggest. But it's still "just space". It doesn't have a "surface" or a distinct "entry point" or any particular features at all, does it?


Note: I appreciate that nothing in "Interstellar" should be taken as a representation of actual real world physics - it was simply the thing that triggered the question about real physics!

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  • $\begingroup$ What you're saying makes sense to me. I would also probably expect a wormhole to emit a lot of nasty ionizing radiation, since that's what's normally expected to destroy objects passing through. $\endgroup$
    – user4552
    Nov 21, 2014 at 22:24
  • $\begingroup$ Why would it emit anything? By the same logic in my question it's just a region in space that happens to connect to some other region in space: what would cause ionisation in the region (after the dispersal of unbelievable rending of space-time that cause the topology change in the first place ;) ) $\endgroup$ Nov 21, 2014 at 22:28
  • $\begingroup$ If anyone's interested, I just found a wonderful movie simulation of what it would look like based on the mental model I have of what is going on: spacetimetravel.org/wurmlochflug/wurmlochflug.html From this, it's clear that if the wormhole is near solid things, then it looks like a visual distortion. But I suspect that if the same simulation were done of a region in space, it would look like any other region in space... $\endgroup$ Nov 21, 2014 at 22:38
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    $\begingroup$ Actually, much of Kip Thorne's involvement in the movie was modeling the warping of light near the black hole, and he may have been consulted on the wormhole sequence (at least, approaching it initially). $\endgroup$
    – HDE 226868
    Nov 21, 2014 at 22:40
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    $\begingroup$ Wouldn't a wormhole have gravitational lensing around the opening, due to the warping of space time? In that sense you would see effects of the wormhole, even if you don't see the wormhole itself $\endgroup$
    – Sean
    Nov 21, 2014 at 22:57

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The site you linked to on the modeling of what theoretical wormholes would look like shows two reasons a wormhole could be visible: 1) the scene you see through it might not match the surroundings on your end, and 2) there's a lot of distortion of the image of any objects which from your perspective are near the "edge" of the wormhole.

enter image description here

Both effects seem to be at play in the interstellar wormhole, if you look at the large image here. For 1), the image shows a bunch of nebula and a greater overall density of stars in the space on the other side, so that makes it stand out against the starfield on our side. And for 2), you can see that there's a lot of visual distortion in the shapes of the nebulas and things near the circular edge, not much at the center.

Kip Thorne, the physicist who was the science consultant for the movie, says in Chapter 15 of The Science of Interstellar that there were three main adjustable parameters or "handles" that they could use to find a look for the wormhole that Christopher Nolan and effects supervisor Paul Franklin liked best: the wormhole's radius, its length, and something called the "lensing width" which is determined by the curvature of space outside each "mouth". But for any given values of those parameters, they used the real theoretical predictions of Einstein's theory of general relativity to determine the wormhole's appearance:

Just as I had done for Gargantua (Chapter 8), I used Einstein's relativistic laws to deduce equations for the paths of light rays around and through the wormhole, and I worked out a procedure for manipulating my equations to compute the wormhole's gravitational lensing and thence what a camera sees when it orbits the wormhole or travels through it. After checking that my equations and procedure produced the kinds of images that I expected, I sent them to Oliver and he wrote computer code capable of creating the quality IMAX images needed for the movie. Eugénie von Tunzelmann added background star fields and images of astronomical objects for the wormhole to lens, and then she, Oliver, and Paul began exploring the influence of my handles.

The book also includes some pictures showing how the visual appearance of the wormhole changes when these three "handles" are adjusted in various ways. In particular he shows that the amount of distortion of objects near the visual edge of the wormhole depends on the "lensing width", which measures the sharpness of the transition from the throat to the space outside the wormhole's mouth--if transition is sharper, so the space outside becomes nearly-flat at fairly short distances, then there's a thinner region of distorted shapes at the edge.

Finally, at the end of the chapter Thorne notes that although they modeled the external appearance accurately, for the trip through the wormhole, the visual effects people took some artistic license, creating "an interpretation informed by simulations with my equations, but altered significantly to add artistic freshness."

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  • $\begingroup$ The link to Thorne's web is fascinating, but I found it deeply disappointing in equal measure that I found the movie we've linked fascinating. While Thorne's words describe what he scientifically assessed a wormhole in deep space would look like, the resulting image on his page - the Intersellar image - is a far cry from that. Rather than "lensing" of the local scene (which would be almost imperceptible due to the low density of stars) it has a strang "bubble-like" edge, and within it it shows photos of "galaxies" ... which are hardly going to look like this at this distance... $\endgroup$ Nov 29, 2014 at 0:00
  • $\begingroup$ @GreenAsJade - I think the things you identify as galaxies were meant to be nebulas, added to give a little more visual interest to the other side of the wormhole. Even if you quibble with what they choose to put as background on the other side, I think that the way the background was distorted when seen through the wormhole, including the "bubble like edge", was calculated accurately in terms of the paths of light rays predicted by general relativity. But as he said, they did tailor the parameters describing the curvature of space around the wormhole to create the visuals Nolan liked best. $\endgroup$
    – Hypnosifl
    Nov 29, 2014 at 2:50
  • $\begingroup$ I agree that they added "stary thingies", and (IMHO) the bubble rim to give it visual interest. Maaaybe the "rim effect" is caused by distortions of the nebulae on the other side, but it doesn't appear that way (in the same way you can clearly see that it is the beach being distorted at the edge of the hole in the movie). I think that this all goes to answer my question this way: a wormhole in (deep) space would likely look like almost nothing at all, unless you happened to notice distortion of a few stars in the field, or in the remote change it impinges on something big. $\endgroup$ Nov 29, 2014 at 4:59
  • $\begingroup$ @GreenAsJade - I don't really understand what part of the edge you're looking at that gives you doubt that it's just distorted nebulae and stars, if you look at the white blotches on the bottom and right and left it looks completely obvious to me they're three nebulae, and if you zoom in you can see compressed starfields in the lower edges between them. The whitish upper edge isn't as obvious but it seems to be an extension of the nebula whose center is around 2 o'clock. I really doubt Kip Thorne would lie about the rendering, since he was honest about the inaccuracy of the interior. $\endgroup$
    – Hypnosifl
    Nov 29, 2014 at 13:50
  • $\begingroup$ I guess you're right. So one could say that if the wormhole in question had an exit point that was very close to a dense nebula field, then it might look like this. Otherwise, it's much more likely to look like nothing, or at most a subtle distortion in the star field. :) $\endgroup$ Nov 29, 2014 at 21:44

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