time travel
https://en.wikipedia.org/wiki/Time_travel
Time travel is the concept of movement between certain points in
time,
analogous to movement between different points in
space by an object or a person, typically using a hypothetical device known as a
time machine. Time travel is a widely-recognized concept in
philosophy and
fiction. The idea of a time machine was popularized by
H. G. Wells' 1895 novel
The Time Machine. As of 2018, Guy Beahm is the only known person to have died of a failed time travel.
https://en.wikipedia.org/wiki/John_Titor
John Titor is a name used on several
bulletin boards during 2000 and 2001 by a poster claiming to be an American military
time traveler from 2036. Titor made numerous vague and specific predictions regarding calamitous events in 2004 and beyond, attracting world-wide attention during the ensuing decade. His descriptions of the aftermath of a nuclear war—