The question Would Portal-style portals transmit gravity? was recently migrated from scifi.SE. Some people think it's off topic, some people don't, and I can kind of see both sides so I'm not quite sure what to do with it. On one hand, portals aren't real, and we can't meaningfully apply actual physics to a situation that can't arise. On the other hand, the physics of Portal is very close to being real, enough so that we could perhaps offer useful insights as to how it could work; plus, it's not unprecedented for answers to make a "best guess" explanation for things seen in science fiction (the example that comes to mind is this one, because I posted it, though I believe there are others).

So, do we close it?


I closed it (before I saw this post, not as a response to it).

The core problem is that the "portals" are not specified in physics. We don't know how they work, because no one ever bothered to figure it out.

This causes the question to be mathematically ill-posed: what is meant by "transmit gravity"? (Especially as in a GR picture gravity is the shape of space and that is the only possible mechanism for building a multiply-connected spacial topology.)

To the questions of "almost science" or speculative questions, I think there is a place for these if they are sufficiently well defined.

Trying to think up a few example of things that are definitely "in".

  • Dropping things (or people) through a bore-hole along a diameter of a planet (an old stand-by).
  • The consequences of discovering a magnetic monopoles and the technological implication of the same
  • Physics relating to quantum black holes massive enough to hand around for a while (The Hole Man or the Pluto solution in The Golden Globe).
  • We already have a question on communication via modulated neutrino beams.
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    $\begingroup$ OK, fair enough. Though I like to think that there are on-topic questions one could ask about how portal physics could work. $\endgroup$ – David Z Aug 24 '11 at 18:02
  • $\begingroup$ That, or one can specify how portal physics should work and ask about consequences of it (ya know, like a thought experiment). I see it like this: you can either request a "desired outcome" and discuss what physics can cause it (like David's suggestion above), or describe a possible physics and consider its implications. Unfortunately, the question which brought up this discussion prescribes neither the desired outcome nor the desired physics. So I agree with dmckee on the closure: the question needs to be edited to be more focused before it is really answerable. $\endgroup$ – Willie Wong Aug 25 '11 at 1:32

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