Time Travel into the Past: How can a wormhole be transformed into a time machine?

In 1988, Kip Thorn and his students published a technical article about traversable wormholes (see here). In their article, they conjectured that if the laws of physics were to permit traversable wormholes they would probably also permit such a wormhole to be transformed into a time machine, which violates causality. This would allow for travel into the past. More than 25 years later, Thorn was involved with the movie Interstellar from its inception and he helped the producer Christopher Nolan and others weave science into the film’s fabric. However, according to Thorn, today almost thirty years have gone by and, the preponderance of evidence still suggests that traversable wormholes are an impossibility.

Wormhole creation would be governed by the laws of quantum gravity. A seemingly plausible scenario entails quantum foam (“foamy” topologies of space-time on length-scales of the order of the Planck length 1.3 x 10-33). One can imagine an advanced civilization pulling a wormhole out of the quantum foam, enlarging it to classical size, and threading it with exotic matter to hold it open. Of course, says Thorn, we do not understand the quantum gravity laws that control the foam, the pull, and the stages of enlargement. Moreover, we do not understand exotic matter very well either.

Thorn suggests the following thought experiment. I am paraphrasing here. Suppose both California desert and Dublin are connected by a wormhole. The two mouths of the wormhole are synchronized. Since the California desert and Dublin are not moving with respect to each other, I in the California desert can synchronize my clock with that of my friend in Dublin. Hence clocks remain synchronized inside the throat and between the two mouths regardless of the outside time. While a wormhole is a single unit connected by a throat, its two mouths open onto places that are totally different from each other. The wormhole throat itself is a single reference system. According to special relativity, we can, therefore, synchronize clocks in this reference system.

wormholes

Mouth in California Desert                             Mouth in Dublin

The images seen through a wormhole’s mouths. Photos by Catherine MacBride and Mark Interrante.

Both mouths look like crystal balls. When I look into my California desert mouth, I see a distorted image of a street in Dublin. That image is brought to me by light that travels through the wormhole from Dublin to California, rather like light traveling through an optical fiber. When you look into your Dublin mouth, you see a distorted image of the trees in the California desert.

In Thorn, Kip, The Science of Interstellar, W. W. Norton & Company, p. 133.

Imagine a situation where the wormhole has been created by an advanced civilization in some future year, say 3000. On January 1, 3000 the wormhole’s two mouths, A and B, are at rest with respect to each other. Subsequently, mouth A remains at rest in Dublin, while mouth B, in California desert, accelerates to near-light speed, then reverses its motion and returns to its original location. Suppose the advanced beings produce this motion by pulling on mouth B gravitationally. I, therefore, take mouth B for a round trip and travel outside the wormhole with mouth B moving at relativistic velocities. Mouth A will not have moved since nothing has been pulling on it. The two mouths A and B of the wormhole are moving with respect to each other, and the wormhole throat now has mouth A at one end and a hole B at the other end. Hence the geometry of the wormhole throat does not change during the whole trip of mouth B so that the length of the wormhole’s throat remains fixed.

Since the two mouths move with respect to each other, time dilation creates a time difference between the clocks next to each mouth. The motion of the mouth is like that of the twins in the standard special-relativistic twin paradox. Outside the wormhole, mouth B ages less than mouth A, but inside the wormhole, the clocks are still synchronized; mouth A and hole B are at rest relative to each other and therefore, both entrances of the wormhole will age equally. If I have traveled with mouth B at close to the speed of light, I might find myself ensconced for many years in the future after returning to my original location in California desert.

I finally return to California desert with mouth B and find I have aged only one day (namely, on the date January 2, 3000, as measured by my own time – my proper time). Suppose that I find myself, on returning to California desert, to have arrived on, say, January 1, 3010 (according to the standard special-relativistic twin paradox). This is the date that appears on the calendar on the wall of an abandoned creepy cabin in the desert. Stepping through mouth B in California desert on January 1, 3010 and emerging out of A in Dublin will take me back in time. I will emerge from A and find that it is January 2, 3000. This is so because it is as seen from Dublin and my clock remains synchronized with the clock in mouth A. Recall that I have aged only one day during the trip (on my subsequent return to California desert, the date was January 2, 3000, as measured by my own time).

Consequently, by traversing the wormhole from mouth B to mouth A, one can travel backward in time, namely one can traverse a closed timelike curve. The same relative aging that occurs in the twin paradox produces, here, closed timelike curves that loop through the wormhole. However, that traveler could never go further back into the past than the year 3000. No traveler can ever go further back in time than the original date of creation of the wormhole.

Fur further reading see my book: General Relativity Conflict and Rivalries: Einstein’s Polemics with Physicists.

How do science fiction writers explain traversable wormholes? In The Strange Days at Blake Holsey High science fiction television program, a group of science students (science club) at a private boarding school have discovered that their science teacher’s office floor has a traversable wormhole that connects major time periods and therefore deposits a traveler back in time to October 4, 1987, April 11, 1977, and October 4, 1879 (when Blake Holsey High and the wormhole were founded). One of the students is getting sucked into the wormhole:

blck

balke

blak

blc

 

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אלברט איינשטיין – דרכו ליחסות Albert Einstein – pathway to theory of relativity

My Einstein and Relativity Papers – Gali Weinstein

Einstein’s Pathway to the Special Theory of Relativity

Einstein’s Pathway to the General Theory of Relativity

The papers describe the genesis and history of special relativity and the discovery and history of general relativity – Einstein chases a light beam, the magnet and conductor thought experiment, Michelson-Morley experiment, emission theory, ether superfluous, Fizeau water-tube experiment, the principle of relativity and the principle of the constancy of the velocity of light (light postulate), The Step, Besso-Einstein meeting, Relativity 1905 paper. 1907 equivalence principle, lift experiments, Galileo principle, coordinate-dependant theory of relativity, Zurich Notebook, Einstein-Grossmann theory (Entwurf theory), deflection of light near the sun, Einstein’s struggles with Entwurf theory, hole argument, 1915 General Theory of Relativity: Hilbert – Einstein, precession or advance of Perihelion of Mercury, how Einstein found the generally covariant field equations, and Einstein’s 1916 general theory of relativity – Mach’s principle, rotating disk thought experiment, and point coincidence argument. These papers do not discuss the affine connection. For a discussion of the affine connection please consult Prof. John Stachel’s works

Philosophyof physics andof Special Relativity – papers discussing philosophical questions about space and time and interpretations of Special Relativity. A rigid body does not exist in the special theory of relativity, distant simultaneity defined with respect to a given frame of reference without reference to synchronized clocks, Einstein synchronization, challenges on Einstein’s connection of synchronization and Lorentz contraction, a theory of relativity without light – Ignatowski, Einstein’s composition of relative velocities – addition theorem for relative velocities, and space of relative velocities, Max Born and rigid body problem, Paul Ehrenfest’s paradox, relativity of simultaneity, Einstein’s clocks: Einstein’s 1905 Clock Paradox, Paul Langevin and the Twin Paradox

Poincaré and EinsteinThe inertial mass-energy equivalence, Lorentz’s theory of the electron violated the principle of action and reaction, Henri Poincaré trying to mend this violation, in 1905 Einstein showed that a change in energy is associated with a change in inertial mass equal to the change in energy divided by c2. Einstein and Poincaré– Method of clocks and their synchronization, Sur la dynamique de l’electron, Dynamics of the Electron, Einstein’s 1905 letter to Conrad Habicht, Poincaré’s 1905 letters to Lorentz, Poincaré’s spacetime mathematical theory of groups, As opposed to Einstein, before 1905 Poincaré stressed the importance of the method of clocks and their synchronization by light signals. Poincaré’s Lorentz group, Poincaré’s La Science et l’hypothèse  – Science and Hypothesis 

Innovation never comes from the established institutions… – Eric Schmidt

מאמרי איינשטיין והיחסות שלי – גלי וינשטיין

דרכו של איינשטיין ליחסות הפרטית.

דרכו של איינשטיין ליחסות הכללית.

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“חידוש אף פעם לא מגיע ממוסדות מוכרים” – אריק שמידט.

Einstein Archives – Jerusalem and Einstein Papers Project – Caltech

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