The original Ellis drainhole [1] has an attractive end and a repulsive end. They are both spherically symmetric and asymptotically flat, i.e. their gravitationa

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 https://en.wikipedia.org/wiki/Ellis_drainhole [2] https://en.wikipedia.org/wiki/Ellis_wormhole https://en.wikipedia.org/wiki/Ellis_wormhole [3] https://arxiv.org/abs/1302.7170 https://arxiv.org/abs/1302.7170