The Time machine project
For quite some time, Ronald Mallett has been working on plans for a time machine. This technology would be based upon a ring laser's properties within the context of Einstein's Theory of Relativity. Mallett first argued that the ring laser would produce a limited amount of frame-dragging which might be measured experimentally, saying:
"In Einstein's General Theory of Relativity, both matter and energy can create a gravitational field. This means that the energy of a light beam can produce a gravitational field. My current research considers both the weak and strong gravitational fields produced by a single continuously circulating unidirectional beam of light. In the weak gravitational field of a unidirectional ring laser, it is predicted that a spinning neutral particle, when placed in the ring, is dragged around by the resulting gravitational field."
In a later paper, he argued that at sufficient energies, the circulating laser might produce not just frame-dragging but also closed timelike curves, allowing time travel into the past:
"For the strong gravitational field of a circulating cylinder of light, I have found new exact solutions of the Einstein field equations for the exterior and interior gravitational fields of the light cylinder. The exterior gravitational field is shown to contain closed timelike lines. The presence of closed timelike lines indicates the possibility of time travel into the past. This creates the foundation for a time machine based on a circulating cylinder of light."
Funding for his program, now known as The Space-time Twisting by Light (STL) project, is progressing. Full details on the project, Mallett's theories, a list of upcoming public lectures and links to popular articles on his work can be found at the Professor's UConn web page, and an illustration showing the concept on which Mallett has designed the time machine can be seen on a Geocities webpage.
He also wrote a book entitled, Time Traveler: A Scientist's Personal Mission to Make Time Travel a Reality, co-written with New York Times best-selling author Bruce B. Henderson, that was first published in 2006. In June 2008, motion picture director Spike Lee's production company announced it had acquired the film rights to Mallett's book. Lee is co-writing the movie script and directing the picture.
In a recent paper by Ken Olum and Allen Everett the authors claimed to have found problems with Mallett's analysis. One of their objections is that the spacetime which Mallett used in his analysis contains a singularity even when the power to the laser is off and is not the spacetime that would be expected to arise naturally if the circulating laser were activated in previously empty space. Mallett has not offered a published response to Olum and Everett, but in his book Time Traveler he mentions that he was unable to directly model the optical fiber or photonic crystal which bends the light's path as it travels through it, so the light circulates around rather than moving in a straight line; as a substitute he chose to include a "line source" (a type of one-dimensional singularity) which would act as a "geometric constraint", bending spacetime in such a way that the light would circulate around on a helix-shaped path in a vacuum. He notes that closed timelike curves are present in a spacetime containing both the line source and the circulating light, while they are not present in a spacetime containing only the line source, so that "the closed loops in time had been produced by the circulating flow of light, and not by the non-moving line source." However, he does not provide any additional argument as to why we should expect to see closed timelike curves in a different spacetime where there is no line source, and where the light is caused to circulate due to passing through a physical substance like a photonic crystal rather than circulating in a vacuum due to the curved spacetime around the line source.
Another objection by Olum and Everett is that even if Mallett's choice of spacetime were correct, the energy required to twist spacetime sufficiently would be huge, and that with lasers of the type in use today the ring would have to be much larger in circumference than the observable universe. At one point Mallett agreed that in a vacuum the energy requirements would be impractical but noted that the energy required goes down as the speed of light goes down. He then argued that if the light is slowed down significantly by passing it through a medium (as in the experiments of Lene Hau where light was passed through a superfluid and slowed to about 17 metres per second) the needed energy would be attainable. However, the physicist J. Richard Gott argues that slowing down light by passing it through a medium cannot be treated as equivalent to lowering the constant c (the speed of light in a vacuum) in the equations of General Relativity, saying:
"One has to distinguish between the speed of light in a vacuum, which is a constant, and through any other medium, which can vary enormously. Light travels more slowly through water than through empty space, for example, but this does not mean that you age more slowly while scuba diving or that it is easier to twist space-time underwater. The experiments done so far don't lower the speed of light in empty space; they just lower the speed of light in a medium and should not make it easier to twist space-time. Thus, it should not take any less mass-energy to form a black hole or a time machine of a given size in such a medium."
Later, Mallett abandoned the idea of using slowed light to reduce the energy, writing that, "For a time, I considered the possibility that slowing down light might increase the gravitational frame dragging effect of the ring laser ... Slow light, however, turned out not to be helpful for my research."
Finally, Olum and Everett note a theorem proven by Stephen Hawking in a 1992 paper on the Chronology Protection Conjecture, which demonstrated that according to General Relativity it should be impossible to create closed timelike curves in any finite region that satisfies the weak energy condition, meaning that the region contains no exotic matter with negative energy. Mallett's original solution involved a spacetime containing a line source of infinite length, so it did not violate this theorem despite the absence of exotic matter, but Olum and Everett point out that the theorem "would, however, rule out the creation of CTC's in any finite-sized approximation to this spacetime."
Ronald L. Mallett
Ronald L. Mallett is a full time professor of physics at the University of Connecticut.
Mallett was born in Roaring Spring, Pennsylvania, on March 3rd, 1945. He lived in the Bronx, New York City. When he was 10 years old, his father died at age 33 of a heart attack. Inspired by a Classics Illustrated comic book version of H.G. Wells' The Time Machine, Mallett resolved to travel back in time to save his father. This idea became a lifelong obsession. His brother is artist Keith Mallett.
In 1973, he received a Ph.D. from Penn State University. Also that year, he received the Graduate Assistant Award for Excellence in Teaching.
In 1975, he was appointed a job at the University of Connecticut as an Assistant Professor, where he continues to work today. His research interests include general relativity, quantum gravity, and time travel.
In 1980, he was promoted to Associate Professor, and since 1987, he has been a full Professor. He has received two grants and many other distinctions.
In 2007, his life story of pursuing a time machine was told on This American Life, episode #324.
He is a member of both the American Physical Society and the National Society of Black Physicists.