Gott also proposed a "time mirror": a time travel device based on the principle of time delays. The device would be situated near a black hole some hundred or more light years from Earth. The device would act as a light collector and would power the light rays deformed and curved by the gravitational depression of the black hole. The collector would then reveal the past as detailed by the photons that had originated from Earth.
Since Gott believes that time travel is not cosmologically excluded, he has presented the possibility that the universe was created out of itself (at a later time). This controversial suggestion was published with Li-Xin Lin, and it was described by Gott as "it would be like having one branch of a tree circle around and grow up to be the trunk. In that way, the universe could be its own mother."
In his own book, Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time, Gott argues that travel to the past is quite possible, although probably only after the construction of a working device (during its existence), and certainly not onto the time traveler's own past timeline (he argues that either the many worlds QM interpretation must be invoked to overcome the Grandfather paradox, or that all time travel remain self-consistent, i.e., one can visit the past, but not change it). Although he is keen to emphasize that time travel itself is a commonplace physical phenomenon, by this he means time travel into the future at varying rates through special relativity, he is not completely committal on the subject of time travel to the past. The book does say that nothing known excludes such travel, but he doesn't completely rule out the possibility that future research may prove it impossible.
Gott first thought of his "Copernicus method" of lifetime estimation in 1969 when stopping at the Berlin Wall and wondering how long it would stand. Instead of extrapolating a set of developments in world geo-politics (futurology), Gott used his relative ignorance to his advantage by saying that the Copernican principle is applicable in cases where nothing is known; unless there was something special about his visit (which he didn't think there was) this gave a 75% chance that he was seeing the wall after the first quarter of its life. Based on its age in 1969 (8 years), Gott left the wall with 75% confidence that it wouldn't be there in 1993 ((8/.25) + 1961).
In fact, the wall was brought down in 1989, and 1993 was the year in which Gott applied his "Copernicus method" to the lifetime of the human race. His paper in Nature was the first to apply the Copernican principle to the survival of humanity; His original prediction gave 95% confidence that the human race would last for between 5100 and 7.8 million years. (Brandon Carter's alternative form of the Doomsday argument was delivered earlier that year, but Gott's derivation was independent.)
He made a major effort subsequently to defend his form of the Doomsday argument from a variety of philosophical attacks, and this debate (like the feasibility of closed time loops) is still ongoing. To popularize the Copernicus method, Gott gave The New Yorker magazine a 95% confidence interval for the closing time of forty-four Broadway and Off Broadway productions based only on their opening dates. He was more or less 95% correct.
He received the President’s Award for Distinguished Teaching in acknowledgment of his work on the National Westinghouse and Intel Science Talent Search high school student science competition. He is an active promoter of the public awareness of science at the popular level, and Princeton students have voted him the school's outstanding professor several times.
Gott is a Presbyterian who distinguishes physical from meta-physical questions by their teleology; he believes () that his writings are entirely scientific (not trespassing into the theology) because the motivation for the way things are (or might be) is never examined.