Assuming that space/time wormholes could exist, wouldn’t they have fantasticly high tidal forces at their mouths? Wouldn’t their gravity be comparable to a black hole of the same size?
As far as I know, the well-known Morris-Thorne wormhole (basically thought up so that Carl Sagan had a plausible way for FTL travel to incorporate into Contact), which are basically black hole/white hole connections (Einstein-Rosen bridges) kept from pinching off by exotic mass with negative energy, would have those strong tidal forces.
But there’s another, lesser known type, the so-called Visser wormhole, constructed by lining the edges of a three dimensional volume, like, for instance, a cube, with exotic matter (he proposed using a type of cosmic string for that purpose), which would have the effect of ‘tearing a hole into spacetime and sewing the edges together’, where you’d only have a very sharp curvature at the edges, but not across the faces, rendering them ‘safe’ for traversal.
I think they don’t have to have large tidal forces. The bigger they are (meaming the more mass is involved), the further away from a singularity you can be and still be within the Schwartzschild (sp?) radius. If that dimension is large enough relative to your own size, you don’t feel much of a tidal force.
The point of tidal forces is that some parts of you are closer than others to the attracting mass, and the 1/r^2 force is therefore greater, and you feel tension along the radius because your closer parts are attracted more strongly than your further parts. If your parts are all approximately the same distance, as a fraction of that distance, you won’t feel so tidal. That is, if your feet are only a tenth of a percent closer than your head is, the forces on your feet won’t be much more than the force on your head. If your feet are half as far from the mass as your head, they’ll feel four times the force your head feels.