Man Made Wormholes
To be traversable, and useful, there are very few properties we want a wormhole to have. First, it must obviously be connected to distant parts of space-time, such as you bedroom to the bathroom, or Earth to Jupiter. Second, it should not contain any even horizons, which would block travel. Third, it should be sufficiently sized so that the gravitational force does not kill human travellers.
The biggest problem we have to solve is keeping our wormholes open. No matter how we make wormholes, gravity tries to close them. Gravity wants to pinch it closed and cut the bridge, leaving only block holes at the end, whether it is a traversable wormhole at both ends. It will try to close unless we have something propping it open.
For very old string theory wormholes, that the cosmic strings job. For manmade wormholes, we need a new ingredient – exotic matter. Exotic matter is stuff that has a negative mass (-m). Positive mass (+m), for example, are people, planets and everything attractive because of gravity. But negative mass (-m) will be repulsive – it will push you away. This makes a kind of anti-gravity that props open our wormholes. Exotic matter must exhort enormous pressure to push space-time open; greater pressure than the centre of neutron stars. With exotic matter, we could weave space-time however we see fit. We may even have a candidate for this exotic matter – the vacuum of space itself.
Quantum Fluctuation itself and empty space create pairs of particles and antiparticles only for them to be annihilated an instance later. The vacuum of space boils them and makes it easy to manipulate them to produce an effect similar to the mass we are looking for (-m). We could use this to stabilise wormholes. Once it is kept open the ends of the wormhole would start together. We would need to move them around in distinct places.