On this week’s Exploration, Dr. Michio Kaku has Dr. Frank Melia on the show to talk about black holes; later, Dr. Richard Gott of Princeton University will be on hand to discuss the possibilites of time travel. Tune in for your Monday ration of science and physics!
Fulvio Melia (born 2 August 1956) is an Italian–American astrophysicist and author. He is Professor of Physics and Astronomy at the University of Arizona and has been an Associate Editor of The Astrophysical Journal Letters. A former Presidential Young Investigator and Sloan Research Fellow, he is the author of six books and 175 refereed articles on theoretical astrophysics.
Melia was born in Gorizia, Italy. He was educated at Melbourne University and Massachusetts Institute of Technology, and held a post-doctoral research position at the University of Chicago, before taking an assistant professorship at Northwestern University in 1987. Moving to the University of Arizona as an associate professor in 1991, he became a full professor in 1993. From 1988 to 1995, he was a Presidential Young Investigator (under President Ronald Reagan), and then an Alfred P. Sloan Research Fellow from 1989 to 1992. He became a Fellow of the American Physical Society in 2002. He is also a Professorial Fellow in the School of Physics, Melbourne University.
From 1996 to 2002, he was a Scientific Editor with the Astrophysical Journal, and has later been an Associate Editor with The Astrophysical Journal Letters. He is also the Chief Editor of the Theoretical Astrophysics series of books at the University of Chicago Press.
In a career that has seen him publish 175 refereed research papers and several books, Melia has made important contributions in High Energy Astronomy and the physics of supermassive black holes. He is especially known for his work on the galactic center, particularly developing a theoretical understanding of the central supermassive black hole, known as Sagittarius A*. With his students and collaborators, he was the first to propose that imaging this object with millimeter-interferometry, which should be feasible within a few years, should prove beyond doubt that it possesses the event horizon predicted by Einstein’s theory of general relativity. His more recent work on the “Rh=ct” alternative cosmology has proved much more controversial.
He is also a well-respected and popular publicist of astronomy and science in general, delivering many lectures at public venues, including museums and planetariums. His books have won several awards of distinction, including the designation of Outstanding Academic Books by the American Library Association, and selection as worldwide astronomy books of the year by Astronomy magazine.
John Richard Gott III (born February 8, 1947 in Louisville, Kentucky) is a professor of astrophysical sciences at Princeton University. He is known for developing and advocating two cosmological theories with the flavor of science fiction: Time travel and the Doomsday argument.
Paul Davies‘s bestseller How to Build a Time Machine credits Gott with the proposal of using cosmic strings to create a time machine. Gott’s machine depends upon the antigravitational tension of the (hypothetical) strings to deform space without attracting nearby objects. The traveler would follow a precise path around rapidly separating strings, and find that he or she had moved backwards in time. Gott’s solution does require that the strings are infinitely long, though: a theorem by Stephen Hawking proves that according to general relativity, closed timelike curves cannot be created in a finite region of space unless there is exotic matter present which violates certain energy conditions, while cosmic strings would not be expected to violate these conditions, so strings of finite length wouldn’t work.
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, as in the Novikov self-consistency principle). 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 (1961 + (8/0.25)).
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/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.