Time Machines

Time travel has two vocabularies. For most of us, it’s Tardises, DeLoreans, and time turners. For scientists, though, it’s wormholes, naked singularities, and closed time-like curves.
Physicists will be tossing those terms around next week at a conference in Italy. They probably won’t come up with a new device for heading back in time. But they may come up with a better understanding of the science behind time travel.
Traveling through time is allowed by General Relativity, Albert Einstein’s theory of gravity.
A naked singularity, for example, would be like the center of a black hole without the surrounding black hole. That would allow you to pass near the dense concentration of matter without getting trapped. Instead, it might fling you elsewhere in time.
A wormhole is like a tunnel — a shortcut connecting not only different points in space, but different points in time. In fact, if wormholes exist, they must be time machines.
A closed time-like curve would bring an object that follow