"These are -- as their name suggests -- string-like objects that some scientists believe were formed in the early universe. These strings may line the entire length of the universe and are under immense pressure -- millions upon millions of tons. These cosmic strings, which are thinner than an atom, would generate an enormous amount of gravitational pull on any objects that pass near them. Objects attached to a cosmic string could travel at incredible speeds, and because their gravitational force distorts spacetime, they could be used for time travel. By pulling two cosmic strings close together, or one string close to a black hole, it might be possible to warp spacetime enough to create closed time-like curves."