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Comment by imglorp | Hacker News Reader

If there are any naturally occurring wormholes, would they have different external properties as compared to black holes?

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The original Ellis drainhole [1] has an attractive end and a repulsive end. They are both spherically symmetric and asymptotically flat, i.e. their gravitational effects fall off with distance like you'd expect, and it wouldn't be immediately obvious from gravity alone that there's anything unusual about the attractive end.

There is a limit case [2] of the drainhole which doesn't gravitate, in the sense that the "attractive" end has vanishing attraction and the "repulsive" end has vanishing repulsion. The wormhole in "Interstellar" was based on that solution [3].

[1] https://en.wikipedia.org/wiki/Ellis_drainhole

[2] https://en.wikipedia.org/wiki/Ellis_wormhole

[3] https://arxiv.org/abs/1302.7170

At the least light should escape a wormhole, and we should "see" what is on the other side. Otherwise I'm not sure how it'd be possible to detect any difference between a wormhole and a blackhole.

Thats the question. Even if wormholes exist, the Universe is under no obligation to make them observable to us. If they are always on the other side of a black hole event horizon, then there would be no way for us to detect them, even in principle.

Would we not be able to infer their existence by finding a white hole? I do see how calling that a detection could be a stretch.

Actually, GR describes white holes, along with black holes, but no ideas how a white hole would form in the real universe apparently exist.

It is true no physical law obligates the universe to make them observable to us. But, this is the same universe that gave rise to Star Trek, Firefly, and especially The Expanse making so many of us dream of interstellar travel. So, I’d say ethically it’s pretty damn obligated to make them observable :)

/s (Sort of.. not really)

Life imitates art, the universe will surely give :)

Firefly is all STL. It’s ambiguous how they got to the system they now occupy.

Wait, really? I haven't watched the show, but aren't there like six different habitable planets involved?

You can't have that all in a single star system.

They kinda try to patch it up in the movie "Serenity". Supposedly the whole show takes place in a gigantic star system full of giants with dozens of moons amounting to hundreds of worlds. They also have some form of terraforming tech to make inhospitable worlds habitable.

Frankly I find that whole set up only slightly more plausible than some kind of FTL, especially since they also have gravity manipulation tech already.

More. All geo engineered. Ambiguous how humanity got to the system though.

That said recent talks about habitable zone around a black hole made me wonder if that would work.

I honestly did not remember that.

Good point.

IIRC it's spelled out somewhere that the colonization fleet was generation ships.

This is the same universe that gave rise to the Tide Pod challenge.

Perhaps in the far future there will be a Find a wormhole challenge where future human teenagers will dive their spaceships into a blackhole they think is in fact the entrance to a wormhoe and scream YOLO just before entering the event horizon.

If they're not observable then they're all unidirectional from here to somewhere over there (or from there to here but there is nothing over there, not even vacuum fluctuations).

If they are undetectable, that is, never ever influence anything in the observable universe, the Occam razor instantly shaves them off.

Would the entry and exit points be orbiting another body somewhere?

They could be. Absent other forces acting on them, they would move along geodesics, like everything else. Near an ordinary massive body, geodesics are orbits.

Popular example: the wormhole in "Interstellar" was orbiting Jupiter.

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